Article: 98417 of rec.radio.amateur.homebrew From: Andrea Baldoni Subject: Re: AGC signal/noise question... References: <44e5cf80$0$13738$5fc30a8@news.tiscali.it> <44e5fe81$0$13715$5fc30a8@news.tiscali.it> <1156043959.936323.84540@75g2000cwc.googlegroups.com> <1156103185.261420.21420@74g2000cwt.googlegroups.com> Message-ID: Date: Fri, 25 Aug 2006 13:06:55 -0500 tim gorman wrote: : Are you sure you are seeing an AGC problem? What you describe above, with : slightly less signal in the center, is typical of a *filter* with dip in I have the filter dip; it was not cured with realigning, but realigning was anyway helpful to gain a dB or two. I also see that disabling AGC cause less noise in FM while listening to 2m converted to HF by the internal converter of the Yaesu FR-101. I didn't check if enabling or disabling AGC cause any change in the filter dip, anyway I'll check and report soon. : Without knowing more about the receiver I can't make any guesses as to what : is in play here but I question if this is an AGC artifact. It uses a MC1496G as mixer and two CA3053 as IF. Plus some DG FETs, in first RF amplifier, after the mixer... What information do you need? Ciao, AB ... Andrea Baldoni, 2002: messaggio non protetto da copyright. Article: 98418 of rec.radio.amateur.homebrew From: tim gorman Subject: Re: AGC signal/noise question... References: <44e5cf80$0$13738$5fc30a8@news.tiscali.it> <44e5fe81$0$13715$5fc30a8@news.tiscali.it> <1156043959.936323.84540@75g2000cwc.googlegroups.com> <1156103185.261420.21420@74g2000cwt.googlegroups.com> Message-ID: <1crnce.972.ln@tg6124.ab0wr.net> Date: Fri, 25 Aug 2006 15:52:22 -0500 Andrea Baldoni wrote: > > > tim gorman wrote: > > : Are you sure you are seeing an AGC problem? What you describe above, > : with slightly less signal in the center, is typical of a *filter* with > : dip in > > I have the filter dip; it was not cured with realigning, but realigning > was anyway helpful to gain a dB or two. > I also see that disabling AGC cause less noise in FM while listening to 2m > converted to HF by the internal converter of the Yaesu FR-101. I didn't > check if enabling or disabling AGC cause any change in the filter dip, > anyway I'll check and report soon. > > : Without knowing more about the receiver I can't make any guesses as to > : what is in play here but I question if this is an AGC artifact. > > It uses a MC1496G as mixer and two CA3053 as IF. Plus some DG FETs, in > first RF amplifier, after the mixer... What information do you need? > > Ciao, > AB > > ... Andrea Baldoni, 2002: messaggio non protetto da copyright. A block diagram would be helpful. Do you know if the AGC is being derived >from the audio chain or from a sampling circuit in the IF chain? Where are you turning off the AGC? In the FR-101? It sounds like you have a frequency converter feeding an HF receiver with an FM position. Is that correct? Could you just as easily tune in 2-m SSB as well as 2-m FM? I can't seem to grasp why turning off the AGC would result in *less* noise, especially on FM. The "noise factor" of the system is probably fixed by the converter, not the receiver. It would be like hooking an antenna to an HF receiver. Usually the noise in the receiver is set by the atmospheric noise the antenna picks up, not by the noise factor of the receiver. (On the higher HF bands, 15m and 10m, this may not always be the case) The same would apply for the 2m converter. Unless it is designed very well its contribution to the noise at the antenna of the receiver would probably mask the noise factor of the receiver itself. If you could kill the power to the converter you could probably test for this by just killing the power and seeing what happens to the noise out of the receiver speaker. If it goes down, then the noise factor of the receiver is irrelevant. If it doesn't change then the converter is contributing less noise than the receiver itself. If turning off the AGC causes less noise output then my first guess would be to look at what "turning off the AGC" is actually doing. Is it actually breaking the AGC loop so the AGC inputs to the CA3053 amps are left floating? Or does turning off the AGC actually mean putting a fixed bias on the CA3053's? Either case could potentially cause the gain of the CA3053's to actually go down with the AGC turned off and that might be what is going on. Can you actually monitor the AGC loop to see what happens to the AGC voltage when the AGC is turned off? tim ab0wr Article: 98419 of rec.radio.amateur.homebrew From: jgboyles@aol.com Subject: Re: Can I use a 120V Variac to get 220V? Date: 25 Aug 2006 14:59:53 -0700 Message-ID: <1156543193.700468.147250@b28g2000cwb.googlegroups.com> References: <1155929463.373199.177360@74g2000cwt.googlegroups.com> > And if you want to see a good textbook using this method, grab a copy > of 'The Art of Engineering" by Horowitz(sp) and Hill. read it - you > might learn something from it about communication skill. > > If you cant help, dont hinder. > > > Andrew VK3BFA. Hi Andrew, don't you mean "grab a copy of 'The Art of Electronics' by Paul Horowitz and Winfield Hill"? As far as I can tell H & H never wrote 'The Art of Engineering'. You made some halfway good points in the age old "me Technician you Engineer" argument, but you lost credibility when you recommended a book that doesn't exsist. Attention to detail, Engineers do, Technicians don't :-). If you can't help, don't hinder. This had nothing to do with the orginal question-sorry. Gary N4AST Article: 98420 of rec.radio.amateur.homebrew From: Rob Subject: QST June 2006 Message-ID: Date: Sat, 26 Aug 2006 11:41:36 GMT Would anyone have a copy of QST June 2006 that they could scan the article about building a homebrew 600 watt amplifier on page 39 or possibly know of a link where I could download it? Thanks, Rob WB8VWI Article: 98421 of rec.radio.amateur.homebrew From: "jack" References: Subject: Re: QST June 2006 Date: Sat, 26 Aug 2006 09:13:35 -0400 Message-ID: Try the Cleveland Public Library. "Rob" wrote in message news:QrWHg.80021$Eh1.71543@tornado.ohiordc.rr.com... > Would anyone have a copy of QST June 2006 that they could scan the > article about building a homebrew 600 watt amplifier on page 39 or > possibly know of a link where I could download it? Thanks, Rob WB8VWI Article: 98422 of rec.radio.amateur.homebrew From: "Wesleywoo-woo" References: <8Y-dnQuvbIz2GHLZnZ2dnUVZ_uydnZ2d@comcast.com> Subject: Re: radiomart descriptions Date: Sat, 26 Aug 2006 09:42:02 -0400 Message-ID: I have a better idea Mike. If you don't like the guy re-selling things he bought at estate sales and other places, simply ignore him. It's just that simple. Go to another Deli and get your Cornbeef on Rye at another store. Life's too short to worry about ham radio dealers that's fer damm sure! :) "mike maghakian" wrote in message news:8Y-dnQuvbIz2GHLZnZ2dnUVZ_uydnZ2d@comcast.com... > look at this auction: > http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=ADME:B:WNA:US:112&item=110023382429&id= > > the seller said he bought it in a radio mart acution and gives the number. > radio mart said it was "stunning" and "excellent" > the seller is now noting all the problems if you read the question section. > > for those of you considering a radiomart auction. consider that he thinks > telling lies is standard operating procedure. > > Article: 98423 of rec.radio.amateur.homebrew From: Andrea Baldoni Subject: Re: AGC signal/noise question... References: <44e5cf80$0$13738$5fc30a8@news.tiscali.it> <44e5fe81$0$13715$5fc30a8@news.tiscali.it> <1156043959.936323.84540@75g2000cwc.googlegroups.com> <1156103185.261420.21420@74g2000cwt.googlegroups.com> <1crnce.972.ln@tg6124.ab0wr.net> Message-ID: <2eCdnYEIhbm7Em3ZRVny2w@kpnqwest.it> Date: Sat, 26 Aug 2006 13:12:54 -0500 tim gorman wrote: : A block diagram would be helpful. Do you know if the AGC is being derived : from the audio chain or from a sampling circuit in the IF chain? The AGC is derived sampling the RF level at the last IF. In the same point, (using another diode, capacitor, etc.) there is the AM detector. The same RF signal go to a diode balanced modulator along with BFO signal for CW and SSB and to the input of FM IF amplifier (TA7061AP). : Where are you turning off the AGC? In the FR-101? It sounds like you have a : frequency converter feeding an HF receiver with an FM position. Is that : correct? Could you just as easily tune in 2-m SSB as well as 2-m FM? I have a FR-101 with the onboard 2m converter. Yes, I could tune 2m SSB but it's difficult to find SSB on 2m here usually so I didn't any test. The FR-101 is CW/SSB/AM/Narrow AM in segments of the HF range, plus you could buy (as a option) a onboard 2m converter, a onboard 6m converter and a onboard FM detector. I have all boards installed, so I eventually could use FM on HF as well as 2m or 6m. : If you could kill the power to the converter you could probably test for : this by just killing the power and seeing what happens to the noise out of : the receiver speaker. If it goes down, then the noise factor of the : receiver is irrelevant. If it doesn't change then the converter is : contributing less noise than the receiver itself. Turning on the 2m converter don't seem to change noise level, while instead turning on the 6m converter seems to double the noise. Maybe it needs realigning, I never use it so I don't know if it's working well. : If turning off the AGC causes less noise output then my first guess would be : to look at what "turning off the AGC" is actually doing. Is it actually The AGC line is derived from a fixed voltage using a 9V zener, then the RF GAIN pot permit to divide this voltage from 100% to ground and feed it (trough a resistor) to the first RF amplifier of the HF receiver (a DG FET) as well as the first RF amplifier of the 2m converter, and the same for 6m converter. It is also fed to the last but one CA3053. Other amplifiers are fixed gain I suppose. Everything in the receiver needs to reduce gain, lower this voltage by more or less shorting it to ground. For instance, the standby button shorts it to ground, silencing the receiver completely. The RF level at the last IF instead reduce it by means of common emitter transistor: the AGC voltage from zener at the collector and the rectified and filtered IF at the base. When you disable AGC, you disconnect the collector of this transistor, thus the signal is let alone to the level adjusted with RF gain pot (normally at maximum, so it is 9V). Ciao, AB ... Andrea Baldoni, 2002: messaggio non protetto da copyright. Article: 98424 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: QST June 2006 Message-ID: References: Date: Sat, 26 Aug 2006 19:20:44 GMT On Sat, 26 Aug 2006 11:41:36 GMT, Rob wrote: >Would anyone have a copy of QST June 2006 that they could scan the >article about building a homebrew 600 watt amplifier on page 39 or >possibly know of a link where I could download it? Thanks, Rob WB8VWI the design is a motorola published design. Communications Concepts also sells parts to make it and has the schematic on their site. Allison Article: 98425 of rec.radio.amateur.homebrew From: Andrea Baldoni Subject: Re: AGC signal/noise question... References: <44e5cf80$0$13738$5fc30a8@news.tiscali.it> <44e5fe81$0$13715$5fc30a8@news.tiscali.it> <1156043959.936323.84540@75g2000cwc.googlegroups.com> <1156103185.261420.21420@74g2000cwt.googlegroups.com> <6tpke2h5uksplnv3ud85rki5nfbdjjnca5@4ax.com> Message-ID: Date: Sat, 26 Aug 2006 14:50:32 -0500 nospam@nouce.bellatlantic.net wrote: : Dual conversion for HF and triple conversion of 2m. There would : not be RF agc on the 2m converter. In FM modes you should see : limiting so agc is behavour is different. By looking closer at the AGC circuits, there is RF AGC also in the 2m and 6m converters. However, the AGC involves not all amplifiers in this receiver, just the first and the last but one. I often see different configurations in receivers, where every amplifier is controlled. Maybe they thought it would suffice. : Likely a test point that is not marked on the board. I don't have : a print handy. I had calibrate it for the minimum voltmeter reading, because it appears that the signal is negative over a positive DC bias, supplied by the JFET. Probably there is another point where the signal is positive, anyway it should be the same. : Having experimented with recievers since before EE school and still : many decades later I find it challenging. Always looking for and at : new ideas. I have read very interesting articles on QEX (by downloading them in PDF format from the site) following back the chain of cross references starting >from "A software defined radio for the masses" to the R1 and R2. Every designer has his own ideas about AGC, dynamic range, et all. Often very different. While I never (as now) tried to design a receiver, I want to carefully understand the reasons behind every implementation. So I could build my own opinion and in future choose what I think better for a receiver project. Anther interesting argument is LO: DDS, PLL or DDS+PLL? Ciao, AB ... Andrea Baldoni, 2002: messaggio non protetto da copyright. Article: 98426 of rec.radio.amateur.homebrew From: "AndyS" Subject: Kenwood ST-1 Base Station schematic Date: 26 Aug 2006 13:20:27 -0700 Message-ID: <1156623627.794705.75480@75g2000cwc.googlegroups.com> Andy asks: Does anyone have a schematic of a Kenwood ST-1, which is the base station stand/charger for a TR2400, that they could Email to me ? Thanks. Andy in Eureka, Texas W4OAH Article: 98427 of rec.radio.amateur.homebrew From: ken scharf Subject: Re: buying stupid in the USA References: <92901$44ecf536$d1cc7c6f$29385@snip.allthenewsgroups.com> Message-ID: Date: Sat, 26 Aug 2006 16:47:42 -0400 bobbbo wrote: > "mike maghakian" wrote in message > news:NaKdnUoccopEXXHZnZ2dnUVZ_q2dnZ2d@comcast.com... >> sometimes people complain when I point out people paying real stupid > prices >> for something on eBay. > > The reason for that is Hamfests and Swap Meets in general are DEAD. > Finished! Kaputski! Stick-a-fork-into-it! (etc..etc..) > Dayton Included too. I went to Dayton this year after a 5 Year sabbatical. > Fully 1/3'rd of the outside vendor spaces were empty. > Just 5 Years ago this was a rarity and 10 years ago it was downright > impossible. > > Why? Reasons are many....aging ham/swl population, SK's, health/travel, > cost > of gas food lodging etc... then again, why drive when you can order new > online > an it's at your door via UPS in a few days? > > Ham radio is changing and it is aging. more than HALF the hams I used > to talk with on 75M HF just from 10 Years ago are all SK's. That alone > speaks volumes folks! > > E-Bay did not kill hamfests. Hams themselves are dying off and > most of the stuff is ending up on e-Bay where it's a feeding frenzy. > This too will end in a few (10?) Years time also. > > In short....Wayne Green (W2NSD) had it right all along folks. > > Enjoy the rest of the ride. > > The various "free flea" ham events that pop up here ins S FL are well attended. They are short and sweet events opening at the crack of dawn and ending by noon. Stuff for sale is a mix of old radios >from the 50's through the 90's (with a few WWII boat anchors here and there), lots of computer crap (who wants pre-pentium stuff these days?), and a few tube vendors. Also the usual guys just cleaning out their junk boxes. Why pay to go to a big ham fest when you can show up at a freebee? I usually don't find any real big bargains, but I do bump into old friends, chew the fat, and usually take home some needed parts for a project. Maybe the flea markets at the big shows are lean because all the sellers have dumped their stuff at the free fleas? It is a pain to have to load up, set up, hang around for two long days and then pack it all back in and go home. With the free fleas you just open your trunk throw a blanket on the floor or open up a folding table or two. 5 or 6 hours later, (not too long a drag) you pack it up and go home. You'll take less stuff to sell, and maybe have to go to a few free fleas to get rid of it all but somehow it seems like less wear and tear on the old body. I still like to go to one big hamfest a year though, just to see what the big vendors have come up with. Article: 98428 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: AGC signal/noise question... Message-ID: References: <44e5cf80$0$13738$5fc30a8@news.tiscali.it> <44e5fe81$0$13715$5fc30a8@news.tiscali.it> <1156043959.936323.84540@75g2000cwc.googlegroups.com> <1156103185.261420.21420@74g2000cwt.googlegroups.com> <6tpke2h5uksplnv3ud85rki5nfbdjjnca5@4ax.com> Date: Sat, 26 Aug 2006 22:01:20 GMT On Sat, 26 Aug 2006 14:50:32 -0500, Andrea Baldoni wrote: >nospam@nouce.bellatlantic.net wrote: > >: Dual conversion for HF and triple conversion of 2m. There would >: not be RF agc on the 2m converter. In FM modes you should see >: limiting so agc is behavour is different. > >By looking closer at the AGC circuits, there is RF AGC also in the 2m >and 6m converters. However, the AGC involves not all amplifiers in this >receiver, just the first and the last but one. I often see different >configurations in receivers, where every amplifier is controlled. >Maybe they thought it would suffice. Often not every amplifier needs to be controlled. It's a matter of van the overall gain change be achieved with fewest control points. > >: Likely a test point that is not marked on the board. I don't have >: a print handy. > >I had calibrate it for the minimum voltmeter reading, because it appears that >the signal is negative over a positive DC bias, supplied by the JFET. >Probably there is another point where the signal is positive, anyway it >should be the same. Generally will be. What I have seen in some cases is where the no signal resting point for gain control bias voltage is not correct and the gain can go up a bit before going down. Often seen on oder recievers where the large part of the radio is discrete devices and the various setpoints have drifited from age or componenet changes. >: Having experimented with recievers since before EE school and still >: many decades later I find it challenging. Always looking for and at >: new ideas. > >I have read very interesting articles on QEX (by downloading them in PDF >format from the site) following back the chain of cross references starting >from "A software defined radio for the masses" to the R1 and R2. I've build R1, R2, MiniR2. I happen to like the miniR2 and use on with the matching T2 in 6m as my highest performing RX. Highest performing in this case is best dynamic range and lowest noise. SDR is an extension of that work. However since most of the digital work is done at low IF (under 50khz) or at baseband all of the frontend, filter and IF issues remain though the tradeoffs may be different. >Every designer has his own ideas about AGC, dynamic range, et all. Often >very different. While I never (as now) tried to design a receiver, I want >to carefully understand the reasons behind every implementation. So I could >build my own opinion and in future choose what I think better for a receiver >project. Very true. What was considered best in class for 1960, 1970, 1980 and so on has changed considerably. However it's possible to use older topologies with newer devices and obtain perfomance unattainable back then. What is easiest to build and make perform is usually a low gain approach using amplifers that do not overload easily to get a balanced dynamic range and noise figure. I've seen too many chase for a high gain for sensitivity at low HF only to be overloaded with man made and atmospheric noise. A good example of a strong staple topology is the Elecraft K2. A very solid single conversion with medium high IF transceiver. The basic design topology is 25 years old (look up Progressive RX, QST) but, it's well executed using current tech parts. The manual is available on line and worth reading and reviewing. >Another interesting argument is LO: DDS, PLL or DDS+PLL? I use Analog with premix for lowest close in noise. Though I also have a DDS with PLL tracking filter and a straight PLL system that has proven satisfactory at my favorite band (6M). In each case considerable care was taken to well shield and filter the signals used while using the best techniques. Executed with care and with an eye for how it fits into the system all work well. Of those (opinion follows) I find DDS has agility and stability with the very noticeable tradeoff for spurious outputs. Due to that I prefer to restrict raw DDS to narrow band systems or clean them up with a tracking PLL. The cost is power, and great care in shielding as the various oscillators and the concurrent need for a microprocessor to do the translation of knobs, buttons and tuning displays into the digital control for DDS can contribute to a lot of undesired signals (birdies). So the whole subject of the LO system can be as complex as the rest of the reciever and be a significant factor in it's total performance. Allison Article: 98429 of rec.radio.amateur.homebrew From: "g. beat" <@> References: Subject: Re: QST June 2006 Date: Sat, 26 Aug 2006 20:07:00 -0500 Message-ID: "Rob" wrote in message news:QrWHg.80021$Eh1.71543@tornado.ohiordc.rr.com... > Would anyone have a copy of QST June 2006 that they could scan the article > about building a homebrew 600 watt amplifier on page 39 or possibly know > of a link where I could download it? > Thanks, Rob WB8VWI Rob, IF you desire to build a solid-state RF amplifier -- it will be for education / build desire -- rather an economics (in other words -- a used Ameritron/MFJ ALS-600 (with 4 MOSFETs) is often much cheaper. It is advisable at 500/600 watt and greater -- that 24/28 VDC or 48/50 VDC RF transistors be used -- lighter gauge wire - less amperage from power supplies. Next read all that you can about Helge Granberg, K7ES(sk) -- Finland's version of Art Collins who wrote most of the Application Notes for Motorola that all other designers have used as the baseline for their designs. http://www.communication-concepts.com/application_notes.htm Amplifier Home building G3TSO (an award winner) http://www.qsl.net/g3tso/HFLinearFrameSet1.html Communication Concepts (supplier of boards referenced in the June 2006 QST article) http://www.communication-concepts.com/ Tom Snowden's 600 watt version -- using the MRF150 RF transistors http://www.k0gkd.com/ssamp.html Pieter Ibelings, N4IP BROADBAND, SOLID STATE AMPLIFIER FOR HF AND 6 METERS http://www.ibelings.com/n4ip/mrf157.html Joel F. Paladino, N6AMG(sk) also had articles on MOSFET design featured in QST and QEX in 1980s (consult back issues) UK design using new power-MOSFETs http://www.picks.force9.co.uk/throb.htm w9gb Article: 98430 of rec.radio.amateur.homebrew From: "g. beat" <@> References: Subject: Re: QST June 2006 Date: Sat, 26 Aug 2006 20:16:35 -0500 Message-ID: "Rob" wrote in message news:QrWHg.80021$Eh1.71543@tornado.ohiordc.rr.com... > Would anyone have a copy of QST June 2006 that they could scan the article > about building a homebrew 600 watt amplifier on page 39 or possibly know > of a link where I could download it? Thanks, Rob WB8VWI Rob - June 2006 QST, page 39 Homebrew Solid-state 600 W HF Amplifier Tom Sowden, K0GKD A low-voltage amp based on one of K7ES' (Helge Granberg -sk) classic application notes . The link to Tom's web site (below) -- will provide not only the article contents but MUCH more than in the QST article ! http://www.k0gkd.com/ssamp.html Article: 98431 of rec.radio.amateur.homebrew From: Rob Subject: Re: QST June 2006 References: Message-ID: Date: Sun, 27 Aug 2006 01:39:43 GMT g. beat <@ wrote: > "Rob" wrote in message > news:QrWHg.80021$Eh1.71543@tornado.ohiordc.rr.com... >> Would anyone have a copy of QST June 2006 that they could scan the article >> about building a homebrew 600 watt amplifier on page 39 or possibly know >> of a link where I could download it? Thanks, Rob WB8VWI > > Rob - > > June 2006 QST, page 39 > Homebrew Solid-state 600 W HF Amplifier > Tom Sowden, K0GKD > A low-voltage amp based on one of K7ES' (Helge Granberg -sk) classic > application notes . > > The link to Tom's web site (below) -- > will provide not only the article contents but MUCH more than in the QST > article ! > http://www.k0gkd.com/ssamp.html > > Thank you for all of the info!! Rob Article: 98432 of rec.radio.amateur.homebrew From: tim gorman Subject: Re: AGC signal/noise question... References: <44e5cf80$0$13738$5fc30a8@news.tiscali.it> <44e5fe81$0$13715$5fc30a8@news.tiscali.it> <1156043959.936323.84540@75g2000cwc.googlegroups.com> <1156103185.261420.21420@74g2000cwt.googlegroups.com> <1crnce.972.ln@tg6124.ab0wr.net> <2eCdnYEIhbm7Em3ZRVny2w@kpnqwest.it> Message-ID: Date: Sat, 26 Aug 2006 21:30:47 -0500 Andrea Baldoni wrote: .................................... > > The AGC line is derived from a fixed voltage using a 9V zener, then the RF > GAIN pot permit to divide this voltage from 100% to ground and feed it > (trough a resistor) to the first RF amplifier of the HF receiver (a DG > FET) as well as the first RF amplifier of the 2m converter, and the same > for 6m converter. It is also fed to the last but one CA3053. Other > amplifiers are fixed gain I suppose. > Everything in the receiver needs to reduce gain, lower this voltage by > more or less shorting it to ground. > For instance, the standby button shorts it to ground, silencing the > receiver completely. The RF level at the last IF instead reduce it by > means of common emitter transistor: the AGC voltage from zener at the > collector and the rectified and filtered IF at the base. > When you disable AGC, you disconnect the collector of this transistor, > thus the signal is let alone to the level adjusted with RF gain pot > (normally at maximum, so it is 9V). > > Ciao, > AB Ok, have you checked the Dual Gate FET to insure that the bias supplied by the RF gain control puts the device at maximum gain when the AGC is off? Dual Gate FET's have transducer gain curves that are peaked curves. Depending upon the Gate 2 voltage, the transducer gain can actually go down as the Gate1 to Source voltage goes up. I would still be interested in knowing *exactly* what the AGC voltage on the gate of the DGFET is for 1) AGC on, no signal, RF gain wide open, and 2) AGC off, no signal, RF gain wide open. It would also be interesting to know what the Gate 1 bias voltage is for each state as well. I'll bet you'll find an interesting interaction between the bias voltages and the actual stage gain as the controls are manipulated. tim ab0wr Article: 98433 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: AGC signal/noise question... Message-ID: References: <44e5fe81$0$13715$5fc30a8@news.tiscali.it> <1156043959.936323.84540@75g2000cwc.googlegroups.com> <1156103185.261420.21420@74g2000cwt.googlegroups.com> <1crnce.972.ln@tg6124.ab0wr.net> <2eCdnYEIhbm7Em3ZRVny2w@kpnqwest.it> Date: Sun, 27 Aug 2006 13:11:46 GMT On Sat, 26 Aug 2006 21:30:47 -0500, tim gorman wrote: >Andrea Baldoni wrote: > >.................................... > >> >> The AGC line is derived from a fixed voltage using a 9V zener, then the RF >> GAIN pot permit to divide this voltage from 100% to ground and feed it >> (trough a resistor) to the first RF amplifier of the HF receiver (a DG >> FET) as well as the first RF amplifier of the 2m converter, and the same >> for 6m converter. It is also fed to the last but one CA3053. Other >> amplifiers are fixed gain I suppose. >> Everything in the receiver needs to reduce gain, lower this voltage by >> more or less shorting it to ground. >> For instance, the standby button shorts it to ground, silencing the >> receiver completely. The RF level at the last IF instead reduce it by >> means of common emitter transistor: the AGC voltage from zener at the >> collector and the rectified and filtered IF at the base. >> When you disable AGC, you disconnect the collector of this transistor, >> thus the signal is let alone to the level adjusted with RF gain pot >> (normally at maximum, so it is 9V). >> >> Ciao, >> AB > >Ok, have you checked the Dual Gate FET to insure that the bias supplied by >the RF gain control puts the device at maximum gain when the AGC is off? > >Dual Gate FET's have transducer gain curves that are peaked curves. >Depending upon the Gate 2 voltage, the transducer gain can actually go down >as the Gate1 to Source voltage goes up. > >I would still be interested in knowing *exactly* what the AGC voltage on the >gate of the DGFET is for 1) AGC on, no signal, RF gain wide open, and 2) >AGC off, no signal, RF gain wide open. It would also be interesting to know >what the Gate 1 bias voltage is for each state as well. Tim, Your hitting the specifics of what I refered to earlier. I'll repeat it for emphasis. What I have seen in some cases is where the no signal resting point for gain control bias voltage is not correct and the gain can go up a bit before going down. Often seen on oder recievers where the large part of the radio is discrete devices and the various setpoints have drifted from age or componenet changes. I have seen this on older radios where parts have been replaced or the original parts used were at opposing ends of the allowable tolerence. Occasionally a part like a zener doide can drift form heating. The end result is the full gain voltage can be off or full gain for a single stage can be off (high or low from optimum). In one case it was a mechanical switch (agc/manual) causing difficulty (leakage path). Other suspect components seen in Japanese built radios are those commonly used ceramic disk caps for bypasses, they can and do go leaky(high resistance), or short and I've even seen microphonic. I have a reciever I repaired where the DGfet developed a substrate to gate2 short which casued all manner of unusual problems. The worst case by far was one that the agc bias point had drifted a bit high. When on manual agc the RX was hot. When agc was enabled the RX sensitvity would drop noticeably. The problem was the higher agc bias point had the IF and RF running harder and producing more noise and when agc was turned on it would see the noise and pull the agc voltage. That sounds ok save for the front end was more agc sensitivve than the overbiased IF and the front end would loose gain faster (it was 2 jfets cascode) rendering the reciever less sensitive. The fix was repairing the internal voltage regulator that fed 9V to most of the circuits (it was running at 11v due to open zener). Just a few examples of what can occur. I havent even gone into the golden screwdriver problems when pots are tweeked for "more". >I'll bet you'll find an interesting interaction between the bias voltages >and the actual stage gain as the controls are manipulated. I'd be inclined to agree. Allison Article: 98434 of rec.radio.amateur.homebrew From: "Rob Mills" Subject: FS: Old/New Hardware Message-ID: Date: Sun, 27 Aug 2006 13:49:10 -0500 I stumbled on to a hand full of old/new parts that I will never use which consist of, 3 ea Millen 39005 universal joint couplings for 1/4 " shafts. 2 ea right angled geared drives that terminate with 2 1/2 " X 1/4" shafts. I believe these to be National parts. 1 ea 5 & 3/4" X 1/8 " flex shaft (can bet cut to length) that has an isolated coupling on each end that will accept 1/4 " shafts. I also believe this to be National part. These are quality items, probably 30 - 40 years old. I'll send any place in the continental US for $20. Rob Mills Article: 98435 of rec.radio.amateur.homebrew From: "Christopher Bucca" Subject: 7854 Tube/Motorola 9TS136401 Schematic? Message-ID: Date: Sun, 27 Aug 2006 19:20:16 GMT Hello all. I'm looking for a circuit schematic to use this tube on 6 meters and 2 meters. So far I'm stumped. I think that this tube was used in some early commercial tansceivers, but I'm not 100% sure. Also would like to know if this is same tube as Motorola P/N 9TS136401 It is the same size as a 5894 but with much thicker plate pins as well as amuch beefier plate structure with an extra fin in the structure for cooling. Even the glass is thicker.I'd even consider buying the final section that used this tube. Any help at all would be greatly appreciated. Thanks and 73 Chris KC2BZH@arrl.net Article: 98436 of rec.radio.amateur.homebrew From: "Christopher Bucca" References: <92901$44ecf536$d1cc7c6f$29385@snip.allthenewsgroups.com> Subject: Re: buying stupid in the USA Message-ID: Date: Sun, 27 Aug 2006 19:29:14 GMT My biggest gripe is that the SAME guys show up selling the SAME old crap that you have seen for the last 4 or 5 years now and the all think that they have stuff made out of pure diamonds. If the rest of us don't buy their overpriced crap then prices would come in line with reality. (getting off soapbox now...;-) Chris KC2BZH@arrl.net Article: 98437 of rec.radio.amateur.homebrew From: Roy Lewallen Subject: Re: AGC signal/noise question... Date: Sun, 27 Aug 2006 13:36:59 -0700 Message-ID: <12f40jd6gilt63c@corp.supernews.com> References: <1155856208.223644.33300@m73g2000cwd.googlegroups.com> <12ef9c4hlloatf4@corp.supernews.com> <-N-dnT3VvvMyr3fZRVnyrg@kpnqwest.it> Andrea Baldoni wrote: > Roy Lewallen wrote: > > : The bottom line is that I'd be hesitant to trust just about any number > : for a "worst case" maximum signal strength. Be sure to test any proposed > : design on 40 meters for a while from your location in Europe. > > Uh. Very interesting, Roy. > Even a receiver with AGC has his own limits and probably what you experienced > would have surely overload most commercial ones... > Some numbers must be fixed, even if very high ones. So, how one could > proceed? If you really want to be rigorous about it, you could set up some kind of logging system, perhaps with an A/D converter and computer connected to a reference antenna and simple detector, to measure and log signal strengths over a long period of time. The tough part would probably be deciding what kind of filter to precede it with; maybe something typical of what you expect to use in a real receiver. Then you could do a statistical analysis on the logged signal strengths. Whether or not that's worth while would be up to you -- it would at least certainly make an interesting article. Or, you could build something and put a coarse step attenuator at the front end, noting how much attenuation you have to apply when operating in order to keep the spurs down. Roy Lewallen, W7EL Article: 98438 of rec.radio.amateur.homebrew From: Roy Lewallen Subject: Re: AGC signal/noise question... Date: Sun, 27 Aug 2006 13:56:50 -0700 Message-ID: <12f41ok8jpb605a@corp.supernews.com> References: <44e5cf80$0$13738$5fc30a8@news.tiscali.it> <44e5fe81$0$13715$5fc30a8@news.tiscali.it> <1156043959.936323.84540@75g2000cwc.googlegroups.com> <1156103185.261420.21420@74g2000cwt.googlegroups.com> <2phhe21tmriborj1ghc22k0lcr3sjdo01v@4ax.com> nospam@nouce.bellatlantic.net wrote: > . . . > It's relevence is I've seen this before and understood it's origin > and also elsehere. The other aspect is that if a commonly > accepted part is not fully understood and can lead to undesired > effects then, why not others. . . Very nearly 30 years ago, I was looking into "feed forward" circuits, a technique developed by someone at Tektronix for ultra-low distortion amplification. It turns out that the topology of the MC1350 is similar to what's needed, and a feed forward amplifier can be made from one plus just a few external components. But even by then, I'd learned that it's risky to use components for other than their intended purpose. So I collected 8 or 10 samples from various vendors (the part was widely sold then), and opened them up. Those in cans were easy, using a little can opener that worked like a tubing cutter. Some of the plastic DIP ones were more difficult, but one of the labs at Tek was able to dissolve the plastic while leaving the chip intact. Then I examined them carefully with an inspection microscope. Here's what I found: 1. There were at least three very different designs. The chip size of the largest was several times that of the smallest. 2. Some designs were inherently better balanced than others. Some had resistive "cross unders" where traces cross, which weren't the same on both sides of the circuit. Based on this, I decided it was too risky to make a design based on that part number, since a vendor could change chip suppliers or designs without notice. Interestingly, about six months later, I got a call from the component engineering group asking if I still had the chips. It seems that one or more of the vendors supplying that part (which was used for other applications at Tek) had changed their design, causing failure of some products and the shutting down of their production lines. Tek was big enough that vendors were often required to give advance notice before such changes, but they hadn't given any notice in this case. I'm bringing this up because I'm hearing the MC1350 being spoken of as though all are the same. It wouldn't surprise me if, after all these years, they're now all being made with one design from one foundry. But those ones in your junk box might be way more different than you think. This is almost certainly true of just about any IC. Roy Lewallen, W7EL Article: 98439 of rec.radio.amateur.homebrew From: "Christopher Bucca" References: Subject: Re: 6v & 90v DC Power supply Message-ID: Date: Sun, 27 Aug 2006 22:09:40 GMT I assume that you do not have the companion AM-65 audio amplifier? Shame, because internal to that unit is a power supply (don't remember the numbers now) that allowed you to operate the AM-65/RT-70 combo from 6, 12 or 24 volts depending on the power supply used. The usually supplied unit used 24 volts (Korean War American military standard elec system). If you can't get the 12 volt version, modification instructions can be found in a 73 Magazine article called "New Orders for the R-108" which was a companion receiver for the big brother of the RT-70, the RT-68. R-108 used the same series of plug in internal power supplies that the AM-65 did. There was also a magazine article in the now defunct as well Ham Radio mag titled "Get on Six Meters-The Easy Way". It dealt with a manpack 6 channel radio of Canadian ancestry that also needed 90 Volts. I have the entire run of that magazine from 1969 to 1990 on cd. If I can figure out how to extract the stuff off the disk, I'll email it to you. Now, the fee for such information..... You will regale me with tales of operation and modification of aforementioned Olive Drab garbed electronic equipment!!! I'll email you later from my own account so that you will get my real email address, or you can use the arrl reflector. 73 Chris KC2BZH@arrl.net "James F. Mayer" wrote in message news:Hg1sf.10532$nm.866@newsread2.news.atl.earthlink.net... > I need to generate 6v DC and 90v DC from a 12v DC automotive > electrical system to power an RT-70A/GRC surplus military radio. I need > about 250 mA at +6 volts and about 75 mA at +90 volts. I was thinking > about using the guts from an old battery back up but it would be a bit of > a kluge. Are there any 90 volt regulators in the 78xx series? How do I > get the voltage up to where I can get something that I can get the 90 > volts from. Getting the 6 volts doesn't seem to be a problem. A 7806 off > the battery should work for that unless any of you can see a problem doing > that. Maybe the common common would be a problem. Right now I'm running > it off of an HP6299A and an HP6236B with commons jumpered. I'd like to be > able to go portable with it. > Article: 98440 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: AGC signal/noise question... Message-ID: References: <44e5cf80$0$13738$5fc30a8@news.tiscali.it> <44e5fe81$0$13715$5fc30a8@news.tiscali.it> <1156043959.936323.84540@75g2000cwc.googlegroups.com> <1156103185.261420.21420@74g2000cwt.googlegroups.com> <2phhe21tmriborj1ghc22k0lcr3sjdo01v@4ax.com> <12f41ok8jpb605a@corp.supernews.com> Date: Mon, 28 Aug 2006 02:25:31 GMT On Sun, 27 Aug 2006 13:56:50 -0700, Roy Lewallen wrote: >nospam@nouce.bellatlantic.net wrote: >> . . . >> It's relevence is I've seen this before and understood it's origin >> and also elsehere. The other aspect is that if a commonly >> accepted part is not fully understood and can lead to undesired >> effects then, why not others. . . > >Very nearly 30 years ago, I was looking into "feed forward" circuits, a >technique developed by someone at Tektronix for ultra-low distortion >amplification. It turns out that the topology of the MC1350 is similar >to what's needed, and a feed forward amplifier can be made from one plus >just a few external components. But even by then, I'd learned that it's >risky to use components for other than their intended purpose. So I >collected 8 or 10 samples from various vendors (the part was widely sold >then), and opened them up. Those in cans were easy, using a little can >opener that worked like a tubing cutter. Some of the plastic DIP ones >were more difficult, but one of the labs at Tek was able to dissolve the >plastic while leaving the chip intact. Then I examined them carefully >with an inspection microscope. Here's what I found: > >1. There were at least three very different designs. The chip size of >the largest was several times that of the smallest. >2. Some designs were inherently better balanced than others. Some had >resistive "cross unders" where traces cross, which weren't the same on >both sides of the circuit. > >Based on this, I decided it was too risky to make a design based on that >part number, since a vendor could change chip suppliers or designs >without notice. > >Interestingly, about six months later, I got a call from the component >engineering group asking if I still had the chips. It seems that one or >more of the vendors supplying that part (which was used for other >applications at Tek) had changed their design, causing failure of some >products and the shutting down of their production lines. Tek was big >enough that vendors were often required to give advance notice before >such changes, but they hadn't given any notice in this case. > >I'm bringing this up because I'm hearing the MC1350 being spoken of as >though all are the same. It wouldn't surprise me if, after all these >years, they're now all being made with one design from one foundry. But >those ones in your junk box might be way more different than you think. > >This is almost certainly true of just about any IC. Roy, That is my engineering experience as well. At the time I did my testing I had Motorola, National and Hitachi parts Some fairly current date codes and a few from early 80s and and while the general behavour was similar I noted differences in gain, overall noise and DC balance as well. The noise increase was enough to be noteable in a particular case but on analysis understandable and to be expected. Then again I date back to when the Fairchild UA703 was a breakthrough gain block for RF. Allison KB!GMX Article: 98441 of rec.radio.amateur.homebrew From: David Subject: Book recommendation please Message-ID: <_1uIg.19044$rP1.12765@news-server.bigpond.net.au> Date: Mon, 28 Aug 2006 04:11:38 GMT Anyone recommend a "decent" book that would cover oscillators, small signal RF amps and matching techniques sufficiently to enable a novice to start experimenting with circuits and have enough detail in the text to tweak the circuits to get them running properly ? I have purchased numerous books and cannot yet find one that is capable of giving me enough clear information to do something useful (Or more to the point, I cannot seem to get onto the same wavelength as these guys). My predominant interest is VHF (150MHz). Low power (1 Watt or less), no valves, no requirement to use rf transformers for matching through the entire circuit. Someone mentioned an analog design book a while ago and that may have been appropriate and I could not remember the title. I thought it was "The art and science of analog circuit design" so I purchased that book and was disappointed to find it was full more of anecdotes of a bunch of well seasoned engineers along with some handy tips. Thanks David Article: 98442 of rec.radio.amateur.homebrew From: dplatt@radagast.org (Dave Platt) Subject: Re: Book recommendation please Date: Mon, 28 Aug 2006 05:15:32 -0000 Message-ID: <12f4uvk56v3l96c@corp.supernews.com> References: <_1uIg.19044$rP1.12765@news-server.bigpond.net.au> >Anyone recommend a "decent" book that would cover oscillators, small >signal RF amps and matching techniques sufficiently to enable a novice >to start experimenting with circuits and have enough detail in the text >to tweak the circuits to get them running properly ? "Experimental Methods in RF Design" by Hayward, Campbell, and Larkin, available from the ARRL, would be a good place to start. It's the successor to the classic "Solid-State Design for the Radio Amateur" >from back in 1977. If you can find copies of Doug Demaw's "Design notebook" and "QRP notebook", there's some good reading there as well. Not as advanced as "Experimental Methods" but perhaps a bit more accessible. Buying a bunch of back issues of QRPp might also be helpful. In a lot of the articles which discuss QRP receiver and transmitters, the authors go into detail about their own particular circuit preferences, tweaks, construction and debugging techniques, etc. For a slightly deeper background, I'd recommend "Troubleshooting Analog Circuits" by Robert Pease. It's not specific to RF but is full of useful tricks and ideas. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! Article: 98443 of rec.radio.amateur.homebrew From: David Subject: Re: Book recommendation please References: <_1uIg.19044$rP1.12765@news-server.bigpond.net.au> <12f4uvk56v3l96c@corp.supernews.com> Message-ID: Date: Mon, 28 Aug 2006 05:59:39 GMT Dave, I do have EMIRFD but find almost all the circuits are based around rf transformers for matching and most of them are low frequency (3MHz etc). Regards David Dave Platt wrote: >> Anyone recommend a "decent" book that would cover oscillators, small >> signal RF amps and matching techniques sufficiently to enable a novice >> to start experimenting with circuits and have enough detail in the text >> to tweak the circuits to get them running properly ? > > "Experimental Methods in RF Design" by Hayward, Campbell, and Larkin, > available from the ARRL, would be a good place to start. It's the > successor to the classic "Solid-State Design for the Radio Amateur" > from back in 1977. > > If you can find copies of Doug Demaw's "Design notebook" and "QRP > notebook", there's some good reading there as well. Not as advanced > as "Experimental Methods" but perhaps a bit more accessible. > > Buying a bunch of back issues of QRPp might also be helpful. In a lot > of the articles which discuss QRP receiver and transmitters, the > authors go into detail about their own particular circuit preferences, > tweaks, construction and debugging techniques, etc. > > For a slightly deeper background, I'd recommend "Troubleshooting > Analog Circuits" by Robert Pease. It's not specific to RF but is full > of useful tricks and ideas. > Article: 98444 of rec.radio.amateur.homebrew From: dplatt@radagast.org (Dave Platt) Subject: Re: Book recommendation please Date: Mon, 28 Aug 2006 06:19:14 -0000 Message-ID: <12f52n26i1ufr42@corp.supernews.com> References: <_1uIg.19044$rP1.12765@news-server.bigpond.net.au> <12f4uvk56v3l96c@corp.supernews.com> >Dave, > >I do have EMIRFD but find almost all the circuits are based around rf >transformers for matching and most of them are low frequency (3MHz etc). For the primary matching stuff, that's true. You might want to look at the sections on crystal filters... if I recall properly, there are some filter arrangements which use an LC match at one or both ends. You might want to dig into the ARRL books on UHF and microwave, and perhaps a copy of the old ARRL VHF manual (out of print but available used). I think, though, that you're probably out on the bleeding edge of amateur experimentation. Not a lot of people are homebrewing VHF gear these days, so there may not be a single book which goes into the sort of circuitry you're interested in with an eye towards from-scratch design work. I'm looking right now at the ARRL VHF Manual's description of a 2-meter portable design, circa 1972 - AM transmitter and superregenerative receiver. It's all solid-state - no tubes. However, as with most such designs I've seen, it has quite a few transformers in it - typically part of single- or double-tuned resonant circuits between the stages. The design seems to do both the tuned filtering, and the impedance matching with the same components - not an unreasonable approach. The oscillator strips in a commercially-built 2-meter FM repeater's transmitter and receiver I tore apart recently use a similar approach. If you really want a transformerless design, I'm sure it can be done, but the necessary L/T/pi matches may end up being more difficult to design, and trickier to tune than a more conventional transformer-based design. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! Article: 98445 of rec.radio.amateur.homebrew From: David Subject: Re: Book recommendation please References: <_1uIg.19044$rP1.12765@news-server.bigpond.net.au> <12f4uvk56v3l96c@corp.supernews.com> <12f52n26i1ufr42@corp.supernews.com> Message-ID: <9myIg.19199$rP1.13973@news-server.bigpond.net.au> Date: Mon, 28 Aug 2006 09:06:13 GMT Dave, At present I have an issue with a Butler emitter follower oscillator at 150MHz. I have Matthy's "Crystal Oscillator Circuits" and Randall Rhea's "Oscillator design and computer simulation" books. Also EMIRFD, "Introduction to RF design by Wes Hayward", "Complete Wireless design by Sayre", "RF design by Boswick", ARRL handbook, VHF/UHF handbook and a few more fundamental electronics and antenna books but try as I might I just cannot seem to ever extract enough information from all these books combined to get a useful result. The Butler design I am looking at has a circuit for 100MHz. I assume this would be close enough to use the same typology but adjust the tuning components for 150MHz. The book mentions tuning near by not at resonance. I have no idea how far "near" is and should it be above or below resonance or does it not matter. He then states the holder capacitance of the crystal is 4.2pF and that he tunes this capacitance out with a 410nH inductor. If I calculate this, I get 600nH inductor to tune out 4.2pF at 100MHz. Why would he use 410nH instead of the larger value ? No mention in the text. He mentions that tuning "near" resonance is achieved with L and Cap from base to emitter. He shows a 8-15pF cap. If I assume the trimmer set about half way at say 12pF and use his value of L of 120nH then the circuit is actually tuned to 132MHz. (I am not sure if this 30% higher frequency is what e really means by "near resonance". He also does not take into account the Base emitter capacitance or the cap to ground of the c-tap. Is the assumption that these do not matter ? I made the circuit with changes in values to try to achieve 150MHz and it worked but had extremely critical tuning (very small adjustment in the tuning C stopped the oscillation). It also appeared to run slightly lower than the stamped marking on the crystal so I assume the either the crystal is cut 100ppm lower for parallel mode or I have not tuned out enough Co or something ? This is where I now need more detail to understand why the circuit behaves like this and what to do to fix it. I would also like to change the bias current as the 19mA current draw is a lot for my application. 5mA would be good but without properly understanding how to calculate Rout of the emitter follower, I am not sure the resistance is getting too high toi drive the crystal. I have tried common base butler designs and they seemed to be easier to get going and understand but several text point out this design is prone to have instabilities and small ranges of inductance in the tuned tank that they will run over. I need to find some text that would cover issues like this but not so deep mathematically that I need a degree to use the math. Thanks Dave Platt wrote: >> Dave, >> >> I do have EMIRFD but find almost all the circuits are based around rf >> transformers for matching and most of them are low frequency (3MHz etc). > > For the primary matching stuff, that's true. > > You might want to look at the sections on crystal filters... if I > recall properly, there are some filter arrangements which use an LC > match at one or both ends. > > You might want to dig into the ARRL books on UHF and microwave, and > perhaps a copy of the old ARRL VHF manual (out of print but available > used). > > I think, though, that you're probably out on the bleeding edge of > amateur experimentation. Not a lot of people are homebrewing VHF gear > these days, so there may not be a single book which goes into the sort > of circuitry you're interested in with an eye towards from-scratch > design work. > > I'm looking right now at the ARRL VHF Manual's description of a > 2-meter portable design, circa 1972 - AM transmitter and > superregenerative receiver. It's all solid-state - no tubes. > However, as with most such designs I've seen, it has quite a few > transformers in it - typically part of single- or double-tuned > resonant circuits between the stages. The design seems to do both the > tuned filtering, and the impedance matching with the same components - > not an unreasonable approach. The oscillator strips in a > commercially-built 2-meter FM repeater's transmitter and receiver I > tore apart recently use a similar approach. > > If you really want a transformerless design, I'm sure it can be done, > but the necessary L/T/pi matches may end up being more difficult to > design, and trickier to tune than a more conventional > transformer-based design. > Article: 98446 of rec.radio.amateur.homebrew From: Roy Lewallen Subject: Re: Book recommendation please Date: Mon, 28 Aug 2006 04:12:42 -0700 Message-ID: <12f5jtci14fijb3@corp.supernews.com> References: <_1uIg.19044$rP1.12765@news-server.bigpond.net.au> It sounds like some of the HP or Motorola app notes might be helpful for this. Maybe someone can suggest some specific ones. Roy Lewallen, W7EL David wrote: > Anyone recommend a "decent" book that would cover oscillators, small > signal RF amps and matching techniques sufficiently to enable a novice > to start experimenting with circuits and have enough detail in the text > to tweak the circuits to get them running properly ? > > I have purchased numerous books and cannot yet find one that is capable > of giving me enough clear information to do something useful (Or more to > the point, I cannot seem to get onto the same wavelength as these guys). > > My predominant interest is VHF (150MHz). Low power (1 Watt or less), no > valves, no requirement to use rf transformers for matching through the > entire circuit. > > Someone mentioned an analog design book a while ago and that may have > been appropriate and I could not remember the title. I thought it was > "The art and science of analog circuit design" so I purchased that book > and was disappointed to find it was full more of anecdotes of a bunch of > well seasoned engineers along with some handy tips. > > Thanks > > David > Article: 98447 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: Book recommendation please Message-ID: References: <_1uIg.19044$rP1.12765@news-server.bigpond.net.au> <12f4uvk56v3l96c@corp.supernews.com> Date: Mon, 28 Aug 2006 12:40:59 GMT On Mon, 28 Aug 2006 05:59:39 GMT, David wrote: > >Dave, > >I do have EMIRFD but find almost all the circuits are based around rf >transformers for matching and most of them are low frequency (3MHz etc). Up to around 200mhz thats not a big issue if properly scaled and the right ferrite used. I've used a lot of ideas from that book at 6 and 2m. The book list presented is one I'd have suggested and added the venerable handbook both current and a few older copies. Allison > >Regards > >David > >Dave Platt wrote: >>> Anyone recommend a "decent" book that would cover oscillators, small >>> signal RF amps and matching techniques sufficiently to enable a novice >>> to start experimenting with circuits and have enough detail in the text >>> to tweak the circuits to get them running properly ? >> >> "Experimental Methods in RF Design" by Hayward, Campbell, and Larkin, >> available from the ARRL, would be a good place to start. It's the >> successor to the classic "Solid-State Design for the Radio Amateur" >> from back in 1977. >> >> If you can find copies of Doug Demaw's "Design notebook" and "QRP >> notebook", there's some good reading there as well. Not as advanced >> as "Experimental Methods" but perhaps a bit more accessible. >> >> Buying a bunch of back issues of QRPp might also be helpful. In a lot >> of the articles which discuss QRP receiver and transmitters, the >> authors go into detail about their own particular circuit preferences, >> tweaks, construction and debugging techniques, etc. >> >> For a slightly deeper background, I'd recommend "Troubleshooting >> Analog Circuits" by Robert Pease. It's not specific to RF but is full >> of useful tricks and ideas. >> Article: 98448 of rec.radio.amateur.homebrew From: David Subject: Re: Book recommendation please References: <_1uIg.19044$rP1.12765@news-server.bigpond.net.au> <12f4uvk56v3l96c@corp.supernews.com> Message-ID: Date: Mon, 28 Aug 2006 13:25:40 GMT Thanks for the feedback. I do not have a ready supply of ferrite cores and do not really want to wind coils. I have surface mountable air fixed coils that provide Q > 100 that I expect should be suitable for most applications and use of trimmer capacitors. The only high frequency crystal oscillator I could find in the EMRFD (100MHz) is page 4.15 which is a common base butler. I understand these suffer parasitic effects, the tank is only effective for a limited range of inductance. The butler emitter follower is offered as a more superior typology but this circuit is not found in this book. The circuit values in his example are incorrect as the 25nH inductor in the tank requires over 100pF to resonate at 100MHz. The circuit shown has a net capacitance of around 40pF ? There is very little design information given with respect to ratio of the C-Tap or emitter bias. I also have his book "Introduction to Radio Frequency design". This does go into more depth but is centred mainly around colpitts oscillators (not good for harmonic crystal oscillators). nospam@nouce.bellatlantic.net wrote: > On Mon, 28 Aug 2006 05:59:39 GMT, David > wrote: > >> Dave, >> >> I do have EMIRFD but find almost all the circuits are based around rf >> transformers for matching and most of them are low frequency (3MHz etc). > > Up to around 200mhz thats not a big issue if properly scaled and the > right ferrite used. > > I've used a lot of ideas from that book at 6 and 2m. The book list > presented is one I'd have suggested and added the venerable handbook > both current and a few older copies. > > Allison > > >> Regards >> >> David >> >> Dave Platt wrote: >>>> Anyone recommend a "decent" book that would cover oscillators, small >>>> signal RF amps and matching techniques sufficiently to enable a novice >>>> to start experimenting with circuits and have enough detail in the text >>>> to tweak the circuits to get them running properly ? >>> "Experimental Methods in RF Design" by Hayward, Campbell, and Larkin, >>> available from the ARRL, would be a good place to start. It's the >>> successor to the classic "Solid-State Design for the Radio Amateur" >>> from back in 1977. >>> >>> If you can find copies of Doug Demaw's "Design notebook" and "QRP >>> notebook", there's some good reading there as well. Not as advanced >>> as "Experimental Methods" but perhaps a bit more accessible. >>> >>> Buying a bunch of back issues of QRPp might also be helpful. In a lot >>> of the articles which discuss QRP receiver and transmitters, the >>> authors go into detail about their own particular circuit preferences, >>> tweaks, construction and debugging techniques, etc. >>> >>> For a slightly deeper background, I'd recommend "Troubleshooting >>> Analog Circuits" by Robert Pease. It's not specific to RF but is full >>> of useful tricks and ideas. >>> > Article: 98449 of rec.radio.amateur.homebrew From: "Joel Kolstad" Subject: Re: Book recommendation please Date: Mon, 28 Aug 2006 09:38:06 -0700 Message-ID: <12f66vf520jl19f@corp.supernews.com> References: <_1uIg.19044$rP1.12765@news-server.bigpond.net.au> Hi David, I've read through the rest of the posts, and in general I think you have a decent selection of books. The couple I'd add: "RF Oscillator Circuit Analysis and Design with Breadboard Experiments" by John Plastonek -- Which is no longer in print, but I could probably scan it in one of these days if you can't find a copy kicking around (I've made active efforts to find this Plastonek guy to ask him about this, and he seems to have dropped off the face of the planet). His oscillator circuits go up to ~100MHz, and he has some discussion as to why you might prefer one oscillator topology over another. "Build Your Own Low-Power Transmitters: Projects for the Electronics Experimenter" by Graf & Sheets (you can preview it on-line at Amazon.com). He has plans in there for transmitters at pretty much all frequency from LF-SHF, and although I haven't build anything in it myself :-), I've heard >from other people that the transmitters really do work. "Practical RF Design Manual" by DeMaw -- Probably overlaps a lot of the of DeMaw books; now distributed by MFJ. BTW, I wouldn't be so quick to give up on RF transformers and matching -- any RF circuit with active components in it is going to require some amount of matching, and while at times you can get away without formally considering it, doing so often gives up power or robustness. (I know it's a little disheartening to open up a commercial radio and see that they managed to achileve something like a stereo FM receiver all in 7 transistors and no RF transformers, but such designs are the evolutionary results of a lot of people spending a lot of time trying to cost minimize a product that's produced in the millions. And keep in mind that something like a cell phone today requires over 100 man years to design...) Finally, don't write off books such as "The Art and Science of Analog Circuit Design" -- it's a great example of one of those books that has a lot of great advice in it, but until you've hit your head on the wall a few thousand times encountering the particular problems the authors have, its value isn't apparent. The sort of "tweaking" advice you're looking for with RF circuits is precisely what TAaSoACD is trying to provide... just more to folks building op-amps & data converters than RF circuit. ---Joel Kolstad Article: 98450 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: Book recommendation please Message-ID: References: <_1uIg.19044$rP1.12765@news-server.bigpond.net.au> <12f4uvk56v3l96c@corp.supernews.com> Date: Mon, 28 Aug 2006 19:36:45 GMT On Mon, 28 Aug 2006 13:25:40 GMT, David wrote: >Thanks for the feedback. > >I do not have a ready supply of ferrite cores and do not really want to >wind coils. >I have surface mountable air fixed coils that provide Q > 100 that I >expect should be suitable for most applications and use of trimmer >capacitors. > >The only high frequency crystal oscillator I could find in the EMRFD >(100MHz) is page 4.15 which is a common base butler. I understand these >suffer parasitic effects, the tank is only effective for a limited range >of inductance. The butler emitter follower is offered as a more superior >typology but this circuit is not found in this book. >The circuit values in his example are incorrect as the 25nH inductor in >the tank requires over 100pF to resonate at 100MHz. The circuit shown >has a net capacitance of around 40pF ? Built as described, it works. However the 25nH is an approximation as distributed C and also lead lengths add significantly. Mine tuned with 33ohms substituted for the crystal from 93 to 122mhz. >There is very little design information given with respect to ratio of >the C-Tap or emitter bias. Read the test as the concepts are outlined rather than how to design xyz circuit in cookbook fashon. If you need help, the easy way is to calculate the reactances at the shown frequency and then using those numbers scale for the desired frequency. The bias point would be the same at any frequency for a given transistor and power. >I also have his book "Introduction to Radio Frequency design". This does >go into more depth but is centred mainly around colpitts oscillators >(not good for harmonic crystal oscillators). In general oscillators in the >20mhz range are harmonic or overtone designs and more subject to parasitic effects. I've bult the 100mhz design and it worked fine for me within the limits of the crystal used though after a x4 multiplication the thermal drift was unacceptable and the crystal was the first order contributor. The oscillator otherwise behaved well. My solution for the whole mess was a lower frequency osc and using low order harmonics. The lower frequency crystale proved both less fussy to oscilate and more stable in fundemental mode. Note: I was interested in sufficient stability to copy SSB at ~1296mhz so even a few dozen Hz drift is noticeable.. Allison > > > > > >nospam@nouce.bellatlantic.net wrote: >> On Mon, 28 Aug 2006 05:59:39 GMT, David >> wrote: >> >>> Dave, >>> >>> I do have EMIRFD but find almost all the circuits are based around rf >>> transformers for matching and most of them are low frequency (3MHz etc). >> >> Up to around 200mhz thats not a big issue if properly scaled and the >> right ferrite used. >> >> I've used a lot of ideas from that book at 6 and 2m. The book list >> presented is one I'd have suggested and added the venerable handbook >> both current and a few older copies. >> >> Allison >> >> >>> Regards >>> >>> David >>> >>> Dave Platt wrote: >>>>> Anyone recommend a "decent" book that would cover oscillators, small >>>>> signal RF amps and matching techniques sufficiently to enable a novice >>>>> to start experimenting with circuits and have enough detail in the text >>>>> to tweak the circuits to get them running properly ? >>>> "Experimental Methods in RF Design" by Hayward, Campbell, and Larkin, >>>> available from the ARRL, would be a good place to start. It's the >>>> successor to the classic "Solid-State Design for the Radio Amateur" >>>> from back in 1977. >>>> >>>> If you can find copies of Doug Demaw's "Design notebook" and "QRP >>>> notebook", there's some good reading there as well. Not as advanced >>>> as "Experimental Methods" but perhaps a bit more accessible. >>>> >>>> Buying a bunch of back issues of QRPp might also be helpful. In a lot >>>> of the articles which discuss QRP receiver and transmitters, the >>>> authors go into detail about their own particular circuit preferences, >>>> tweaks, construction and debugging techniques, etc. >>>> >>>> For a slightly deeper background, I'd recommend "Troubleshooting >>>> Analog Circuits" by Robert Pease. It's not specific to RF but is full >>>> of useful tricks and ideas. >>>> >> Article: 98451 of rec.radio.amateur.homebrew From: "SparkySKO" Subject: Beginner Radio w/o using air variable cap??? Date: 28 Aug 2006 14:42:55 -0700 Message-ID: <1156801375.566432.201790@m73g2000cwd.googlegroups.com> Hello All, [Basically this says, are there any practical alternatives to an air variable capacitor that a beginner can use in building his first receiver radio?] I'm interested in getting my feet wet in building a receiver, but don't want to buy a 'kit'. I'd like to build a radio that has a knob I can somewhat tune it with. I've been really looking at regenerative radios and superheterodynes, although a simple radio is more important than how well it really performs. One common theme in almost every 'simple' radio design I can find, is that they *ALL* use Air variable capacitors. While I'm sure these were everywhere 20 years ago, going to every major electronics supply house in Portland, Oregon has yielded me only with small trimmer capacitors, which AFAIK, will not do for a 'tuner'. I'm aware I can order online for about 10-20$ and purchase an air variable, but I'd like to see if any of you have any suggestions on what might work as an alternative? Varactor diode seemed like a neat idea, although I guess they suffer >from temperature fading. Would this make it impratical for a shortwave or AM receiver? Can you even make a regenerative radio out of a varactor? (Actually, I'll try ghetto rigging a red LED for a varactor, since I don't really care about it being nicely linear, I just want something with a knob that does something!). Can anyone recommend any type of reasonably simple radio (simple mostly as in reasonably low parts count, i don't need an LCD readout) that could possibly be done with parts that can be had at a reasonably stocked electronics store. (Much more inventory than Fry's). A knob is important, I don't want to build one of those ghetto radios with the coil and a metal bead that I slide along the coil to 'tune' it. Any other way to use a potentiometer to tune a radio? Article: 98452 of rec.radio.amateur.homebrew Date: Mon, 28 Aug 2006 15:11:26 -0700 From: Tim Wescott Subject: Re: Beginner Radio w/o using air variable cap??? References: <1156801375.566432.201790@m73g2000cwd.googlegroups.com> Message-ID: SparkySKO wrote: > Hello All, > > [Basically this says, are there any practical alternatives to an air > variable capacitor that a beginner can use in building his first > receiver radio?] > > I'm interested in getting my feet wet in building a receiver, but don't > want to buy a 'kit'. I'd like to build a radio that has a knob I can > somewhat tune it with. I've been really looking at regenerative radios > and superheterodynes, although a simple radio is more important than > how well it really performs. > > One common theme in almost every 'simple' radio design I can find, is > that they *ALL* use Air variable capacitors. While I'm sure these were > everywhere 20 years ago, going to every major electronics supply house > in Portland, Oregon has yielded me only with small trimmer capacitors, > which AFAIK, will not do for a 'tuner'. I'm aware I can order online > for about 10-20$ and purchase an air variable, but I'd like to see if > any of you have any suggestions on what might work as an alternative? > > Varactor diode seemed like a neat idea, although I guess they suffer > from temperature fading. Would this make it impratical for a shortwave > or AM receiver? Can you even make a regenerative radio out of a > varactor? (Actually, I'll try ghetto rigging a red LED for a varactor, > since I don't really care about it being nicely linear, I just want > something with a knob that does something!). > > Can anyone recommend any type of reasonably simple radio (simple mostly > as in reasonably low parts count, i don't need an LCD readout) that > could possibly be done with parts that can be had at a reasonably > stocked electronics store. (Much more inventory than Fry's). A knob is > important, I don't want to build one of those ghetto radios with the > coil and a metal bead that I slide along the coil to 'tune' it. Any > other way to use a potentiometer to tune a radio? > If you want to build a radio circuit without much circuitry you really have to put up with either a variable cap or a variable coil. I'd say you either have to scrounge something or buy one -- they're really not that spendy. Yes, you can go the varactor route, and folks have made it work well. But you have to add more components, it'll never be the same, and you'll have to tinker with it to keep it from drifting all over the place. For a 1st-time radio it may not be a bad thing, but after that I'd go with a real variable element. As far as your complaints about 'ghetto' radios -- your ability to build a high-quality, good looking tunable element is a matter of the talent that you were born with and the effort you take to use it. If you want to build something without many components then you're going to need to work at it anyway. Having said that I wouldn't build -- I'd buy. Have you checked with Cascade Surplus Electronics in North Portland? It's been ages since I've been in there, so I can't guarantee anything. You may also want to try R 5-D 3 Electronic Surplus out in Southeast. He's got lots of old stuff there, if he doesn't have a variable cap he'll have some piece of crud that you can buy and harvest the caps. After those two, consider going to yard and garage sales, buying old radios, and tearing out their capacitors. Stereo tuners from the 70's and 80's are best -- if it's big and has a knob, chances are it has a cap. If it receives FM and it's big and has a knob , chances are the cap will be a good size for shortwave. You may even find that it has a cap with a built-in reduction drive which is cool if you want to tune in CW. Good luck. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/ "Applied Control Theory for Embedded Systems" came out in April. See details at http://www.wescottdesign.com/actfes/actfes.html Article: 98453 of rec.radio.amateur.homebrew From: "laura halliday" Subject: Re: Beginner Radio w/o using air variable cap??? Date: 28 Aug 2006 16:23:52 -0700 Message-ID: <1156807432.877350.199500@m73g2000cwd.googlegroups.com> References: <1156801375.566432.201790@m73g2000cwd.googlegroups.com> SparkySKO wrote: > Hello All, > > [Basically this says, are there any practical alternatives to an air > variable capacitor that a beginner can use in building his first > receiver radio?] > > I'm interested in getting my feet wet in building a receiver, but don't > want to buy a 'kit'. I'd like to build a radio that has a knob I can > somewhat tune it with. I've been really looking at regenerative radios > and superheterodynes, although a simple radio is more important than > how well it really performs. > > One common theme in almost every 'simple' radio design I can find, is > that they *ALL* use Air variable capacitors. While I'm sure these were > everywhere 20 years ago, going to every major electronics supply house > in Portland, Oregon has yielded me only with small trimmer capacitors, > which AFAIK, will not do for a 'tuner'... I'd try R5D3 first, then see if I could find something worth cannibalizing at Cascade (note new address) or Wacky Willy's (lots of junk, but you never know...). Then I'd hit the various thrift stores and see if I could find an old FM tuner. Are there any ham radio swap meets coming up? If you go to R5D3, they really are on a residential side street out in the middle of nowhere. The parts are out there. Go get them! Laura Halliday VE7LDH "Que les nuages soient notre Grid: CN89mg pied a terre..." ICBM: 49 16.05 N 122 56.92 W - Hospital/Shafte Article: 98454 of rec.radio.amateur.homebrew From: David Subject: Re: Book recommendation please References: <_1uIg.19044$rP1.12765@news-server.bigpond.net.au> <12f4uvk56v3l96c@corp.supernews.com> Message-ID: <28LIg.19507$rP1.18962@news-server.bigpond.net.au> Date: Mon, 28 Aug 2006 23:38:38 GMT From what I understand so far the bias should should not necessarily be the same and the capacitors will not scale as suggested. The ESR of the crystal would be different for different overtone crystals so therefore the bias should change to provide correct drive and C to ground on the C-Tap would also need to change. According to Matthy the Cap to ground should be 0.5 to 1 x ESR and emitter drive impedance less than ESR. Or have I misinterpreted something here ? I am also unsure of whether the tank should be tuned above or below resonance. Rhea's book suggests the tank should be capacitive at Fo indicating the tank itself would be tuned above the operating frequency. I would like to learn more about the Butler emitter follower crystal oscillator. If I ask the specific questions about this typology and someone gives me an answer, where did they obtain this information. Have they learned by just playing with the circuit in a hit and miss fashion or have they first obtained fundamental information from some text and using what they have learnt then played with the circuit. If so, what would this text be ? If Ro = Rsource/(beta+1), is Rsource in the oscillator case of the emitter follower Rp of the coil in parallel with the bias resistance or does it also include (Rphi+RE) x Beta. Is Beta used here an approximation calculate by Ft/F ? nospam@nouce.bellatlantic.net wrote: > On Mon, 28 Aug 2006 13:25:40 GMT, David > wrote: > >> Thanks for the feedback. >> >> I do not have a ready supply of ferrite cores and do not really want to >> wind coils. >> I have surface mountable air fixed coils that provide Q > 100 that I >> expect should be suitable for most applications and use of trimmer >> capacitors. >> >> The only high frequency crystal oscillator I could find in the EMRFD >> (100MHz) is page 4.15 which is a common base butler. I understand these >> suffer parasitic effects, the tank is only effective for a limited range >> of inductance. The butler emitter follower is offered as a more superior >> typology but this circuit is not found in this book. >> The circuit values in his example are incorrect as the 25nH inductor in >> the tank requires over 100pF to resonate at 100MHz. The circuit shown >> has a net capacitance of around 40pF ? > > Built as described, it works. However the 25nH is an approximation > as distributed C and also lead lengths add significantly. Mine tuned > with 33ohms substituted for the crystal from 93 to 122mhz. > >> There is very little design information given with respect to ratio of >> the C-Tap or emitter bias. > > Read the test as the concepts are outlined rather than how to design > xyz circuit in cookbook fashon. If you need help, the easy way is > to calculate the reactances at the shown frequency and then using > those numbers scale for the desired frequency. The bias point would > be the same at any frequency for a given transistor and power. > >> I also have his book "Introduction to Radio Frequency design". This does >> go into more depth but is centred mainly around colpitts oscillators >> (not good for harmonic crystal oscillators). > > In general oscillators in the >20mhz range are harmonic or overtone > designs and more subject to parasitic effects. I've bult the 100mhz > design and it worked fine for me within the limits of the crystal used > though after a x4 multiplication the thermal drift was unacceptable > and the crystal was the first order contributor. The oscillator > otherwise behaved well. > > My solution for the whole mess was a lower frequency osc > and using low order harmonics. The lower frequency crystale proved > both less fussy to oscilate and more stable in fundemental mode. > Note: I was interested in sufficient stability to copy SSB at ~1296mhz > so even a few dozen Hz drift is noticeable.. > > Allison >> >> >> >> >> nospam@nouce.bellatlantic.net wrote: >>> On Mon, 28 Aug 2006 05:59:39 GMT, David >>> wrote: >>> >>>> Dave, >>>> >>>> I do have EMIRFD but find almost all the circuits are based around rf >>>> transformers for matching and most of them are low frequency (3MHz etc). >>> Up to around 200mhz thats not a big issue if properly scaled and the >>> right ferrite used. >>> >>> I've used a lot of ideas from that book at 6 and 2m. The book list >>> presented is one I'd have suggested and added the venerable handbook >>> both current and a few older copies. >>> >>> Allison >>> >>> >>>> Regards >>>> >>>> David >>>> >>>> Dave Platt wrote: >>>>>> Anyone recommend a "decent" book that would cover oscillators, small >>>>>> signal RF amps and matching techniques sufficiently to enable a novice >>>>>> to start experimenting with circuits and have enough detail in the text >>>>>> to tweak the circuits to get them running properly ? >>>>> "Experimental Methods in RF Design" by Hayward, Campbell, and Larkin, >>>>> available from the ARRL, would be a good place to start. It's the >>>>> successor to the classic "Solid-State Design for the Radio Amateur" >>>>> from back in 1977. >>>>> >>>>> If you can find copies of Doug Demaw's "Design notebook" and "QRP >>>>> notebook", there's some good reading there as well. Not as advanced >>>>> as "Experimental Methods" but perhaps a bit more accessible. >>>>> >>>>> Buying a bunch of back issues of QRPp might also be helpful. In a lot >>>>> of the articles which discuss QRP receiver and transmitters, the >>>>> authors go into detail about their own particular circuit preferences, >>>>> tweaks, construction and debugging techniques, etc. >>>>> >>>>> For a slightly deeper background, I'd recommend "Troubleshooting >>>>> Analog Circuits" by Robert Pease. It's not specific to RF but is full >>>>> of useful tricks and ideas. >>>>> > Article: 98455 of rec.radio.amateur.homebrew From: "Greg Neill" References: <1156801375.566432.201790@m73g2000cwd.googlegroups.com> Subject: Re: Beginner Radio w/o using air variable cap??? Date: Mon, 28 Aug 2006 20:25:56 -0400 Message-ID: <44f3882d$0$24197$9a6e19ea@news.newshosting.com> "SparkySKO" wrote in message news:1156801375.566432.201790@m73g2000cwd.googlegroups.com... > Hello All, > > [Basically this says, are there any practical alternatives to an air > variable capacitor that a beginner can use in building his first > receiver radio?] Go here: http://www.tubesandmore.com/ and check under Capacitors --> variable. Article: 98456 of rec.radio.amateur.homebrew From: mcalhoun@ksu.edu Subject: Re: Beginner Radio w/o using air variable cap??? Date: 28 Aug 2006 22:12:39 -0500 Message-ID: References: <1156801375.566432.201790@m73g2000cwd.googlegroups.com> "SparkySKO" writes: >[Basically this says, are there any practical alternatives to an air >variable capacitor that a beginner can use in building his first >receiver radio?] >....[snip].... For TWO BUCKS I bought a whole box full of cheapie "transistor radios" >from a church rummage sale a few weeks ago (most were about the size of a man's wallet, but a few were about the size of a thick book), and ALL OF THEM HAD AN AIR-VARIABLE TUNING CAPACITOR! Don't fight a battle you don't need to fight; just tear up an old "transistor radio"! (Now the NEWER transistor radios -- the kind you buy at WalMart for a buck each that have a "push to tune to the next station" button -- do NOT have air-variable capacitors, but the OLDER ones do!) -- --Myron A. Calhoun, W0PBV. Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge NRA Life Member and Rifle, Pistol, & Home Firearm Safety Certified Instructor Certified Instructor for the Kansas Concealed-Carry Handgun license Article: 98457 of rec.radio.amateur.homebrew From: "copdoc1@optonline.net" Subject: WTB COBRA 148 GTL Philippines Made Date: 29 Aug 2006 00:54:40 -0700 Message-ID: <1156838080.181440.287260@75g2000cwc.googlegroups.com> I am looking to purchase 1 or 2 Cobra 148 GTL units that were made in the Philippines. If you have or know of someone that has please contact me at copdoc1@optonline.net Thank You Peter Article: 98458 of rec.radio.amateur.homebrew From: "Leon" Subject: Re: Beginner Radio w/o using air variable cap??? Date: 29 Aug 2006 03:21:41 -0700 Message-ID: <1156846901.774589.229910@b28g2000cwb.googlegroups.com> References: <1156801375.566432.201790@m73g2000cwd.googlegroups.com> SparkySKO wrote: > Hello All, > > [Basically this says, are there any practical alternatives to an air > variable capacitor that a beginner can use in building his first > receiver radio?] > > I'm interested in getting my feet wet in building a receiver, but don't > want to buy a 'kit'. I'd like to build a radio that has a knob I can > somewhat tune it with. I've been really looking at regenerative radios > and superheterodynes, although a simple radio is more important than > how well it really performs. > > One common theme in almost every 'simple' radio design I can find, is > that they *ALL* use Air variable capacitors. While I'm sure these were > everywhere 20 years ago, going to every major electronics supply house > in Portland, Oregon has yielded me only with small trimmer capacitors, > which AFAIK, will not do for a 'tuner'. I'm aware I can order online > for about 10-20$ and purchase an air variable, but I'd like to see if > any of you have any suggestions on what might work as an alternative? > > Varactor diode seemed like a neat idea, although I guess they suffer > from temperature fading. Would this make it impratical for a shortwave > or AM receiver? Can you even make a regenerative radio out of a > varactor? (Actually, I'll try ghetto rigging a red LED for a varactor, > since I don't really care about it being nicely linear, I just want > something with a knob that does something!). > > Can anyone recommend any type of reasonably simple radio (simple mostly > as in reasonably low parts count, i don't need an LCD readout) that > could possibly be done with parts that can be had at a reasonably > stocked electronics store. (Much more inventory than Fry's). A knob is > important, I don't want to build one of those ghetto radios with the > coil and a metal bead that I slide along the coil to 'tune' it. Any > other way to use a potentiometer to tune a radio? Varying the inductance by moving a core in and out of the coil works just as well, and is quite easy to make at home. Leon Article: 98459 of rec.radio.amateur.homebrew From: "xpyttl" References: <1156801375.566432.201790@m73g2000cwd.googlegroups.com> Subject: Re: Beginner Radio w/o using air variable cap??? Message-ID: Date: Tue, 29 Aug 2006 07:37:13 -0400 "Tim Wescott" wrote in message news:Jq6dnWEwlYtg9G7ZnZ2dnUVZ_v2dnZ2d@web-ster.com... > Yes, you can go the varactor route, and folks have made it work well. But > you have to add more components, it'll never be the same, and you'll have > to tinker with it to keep it from drifting all over the place. Varactors are not that tough, and don't mistake the "never be the same". Good varactor rigs are much more pleasant than anything with a variable cap. (Although there are plenty of bad varactor designs out there!) Yes, sometimes there are a couple more components, but not many more. It does take some work to get a varactor oscillator close to drift-free, but five minutes with a calculator will get you close enough for SWLing. Oh by the way, getting a capacitor oscillator close to drift free can be a challenge, especially if you don't have hard-to-get air inductors, and microphonics in that case can be a challenge, too. The larger size of the variable cap/air inductor makes mechanical construction details a lot more important. There's really no free lunch. Varactors do have some temperature coefficient, and they are often coupled with toroid inductors, which also have some considerable temperature coefficient. Most of the designs you see out there are for CW rigs in the ham bands, where temperature stability is extremely important. The maze of capacitors around the varactor are there to balance the temperature coefficients. Usually there is a polystyrene capacitor which has a temperature coefficient opposite to the toroid and varactor, but you can never get exactly the right value for that, so it is a question of getting the right combination of positive and negative temperature coefficients AND the right value of capacitance. For AM in the broadcast band, you can probably come close enough with one or two capacitors. For a rig with a 200 Hz CW filter at 15 meters, it can be a real bear keeping the frequency to within the 0.0001% that you need for comfortable operation. That being said, it is undoubtedly easier to use a variable cap, and caps can be cannabalized from old radios easily and cheaply. Leon also mentions the possibility of making a variable inductor. Actually, from time to time articles have appeared about making variable caps, too. In either case, though, you will need considerable mechanical skills. One thing that makes projects hard, especially your first projects, is this idea that you need exactly the right part. With a little help from your trusty calculator, you can play pretty fast and loose with parts values in most projects. In the case of a tuning cap, if you can find something on the right planet it typically isn't too tough to make adjustments to accomodate the different part. Study your circuit and understand what each part is doing, especially around the tuning circuits. It is usually pretty simple to make some adjustments, especially if, as you suggest, getting some precise tuning range isn't critical. .. Article: 98460 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: Book recommendation please Message-ID: References: <_1uIg.19044$rP1.12765@news-server.bigpond.net.au> <12f4uvk56v3l96c@corp.supernews.com> <28LIg.19507$rP1.18962@news-server.bigpond.net.au> Date: Tue, 29 Aug 2006 12:04:46 GMT On Mon, 28 Aug 2006 23:38:38 GMT, David wrote: > From what I understand so far the bias should should not necessarily be >the same and the capacitors will not scale as suggested. > >The ESR of the crystal would be different for different overtone >crystals so therefore the bias should change to provide correct >drive and C to ground on the C-Tap would also need to change. According >to Matthy the Cap to ground should be 0.5 to 1 x ESR and emitter drive >impedance less than ESR. Or have I misinterpreted something here ? The DC bias would be unchanged. The feedback required may need to be altered but thats a product of frequency and transistor(or fet) gain at the target frequency and any change in overtone used. In short if the circuit shown uses a 100mhz crystal in a 7th overtone mode it will scale if a 89mhz 7th overtone crystal is used. Usually for a narrow range of frequencies like that the ERS varies but not greatly. This does not cover the difference between good quality crystal and poor quality crystals, If you going to use poor quality crystals there may be other issues to investigate as well. >I am also unsure of whether the tank should be tuned above or below >resonance. Rhea's book suggests the tank should be capacitive at Fo >indicating the tank itself would be tuned above the operating frequency. Believe it or not, doesn't matter. You'll build it and then have to tune it for proper oscillation. At around 100mhz the circuit parasitics such as coil construction, PC board trace capacitance and inductance, transistor characteristics, transistor, coil and capactior lead length are all in the mix. >I would like to learn more about the Butler emitter follower crystal >oscillator. > >If I ask the specific questions about this typology and someone gives me >an answer, where did they obtain this information. Have they learned by >just playing with the circuit in a hit and miss fashion or have they >first obtained fundamental information from some text and using what >they have learnt then played with the circuit. If so, what would this >text be ? Generally I try to avoid high order oscilators(overtone) as stability and the need for being tuned doesn't suit my needs. I've never seen a in depth analysis in any one book. I apply my EE training plus 30+ years of theory vs what really happens and go from there. Sometimes being an engineer is really more like science where you observe and build or search out theory to explain the observed behavour, or you break out the diddle stick and adjust it and move on to bigger problems. >If Ro = Rsource/(beta+1), is Rsource in the oscillator case of the >emitter follower Rp of the coil in parallel with the bias resistance >or does it also include (Rphi+RE) x Beta. Is Beta used here an >approximation calculate by Ft/F ? Thats all first order rule of thumb. However, are you trying to build one working oscillator or flog it to death? I say that as I've found it to be both less than an exact science and that accurate to more than 3 decimal places is excess for operation. For one oscillator it is both easy and practical to dead bug it and see if it meets your needs. If you going to build in quantity something using it that is a whole different set of issues. Allison > > > > >nospam@nouce.bellatlantic.net wrote: >> On Mon, 28 Aug 2006 13:25:40 GMT, David >> wrote: >> >>> Thanks for the feedback. >>> >>> I do not have a ready supply of ferrite cores and do not really want to >>> wind coils. >>> I have surface mountable air fixed coils that provide Q > 100 that I >>> expect should be suitable for most applications and use of trimmer >>> capacitors. >>> >>> The only high frequency crystal oscillator I could find in the EMRFD >>> (100MHz) is page 4.15 which is a common base butler. I understand these >>> suffer parasitic effects, the tank is only effective for a limited range >>> of inductance. The butler emitter follower is offered as a more superior >>> typology but this circuit is not found in this book. >>> The circuit values in his example are incorrect as the 25nH inductor in >>> the tank requires over 100pF to resonate at 100MHz. The circuit shown >>> has a net capacitance of around 40pF ? >> >> Built as described, it works. However the 25nH is an approximation >> as distributed C and also lead lengths add significantly. Mine tuned >> with 33ohms substituted for the crystal from 93 to 122mhz. >> >>> There is very little design information given with respect to ratio of >>> the C-Tap or emitter bias. >> >> Read the test as the concepts are outlined rather than how to design >> xyz circuit in cookbook fashon. If you need help, the easy way is >> to calculate the reactances at the shown frequency and then using >> those numbers scale for the desired frequency. The bias point would >> be the same at any frequency for a given transistor and power. >> >>> I also have his book "Introduction to Radio Frequency design". This does >>> go into more depth but is centred mainly around colpitts oscillators >>> (not good for harmonic crystal oscillators). >> >> In general oscillators in the >20mhz range are harmonic or overtone >> designs and more subject to parasitic effects. I've bult the 100mhz >> design and it worked fine for me within the limits of the crystal used >> though after a x4 multiplication the thermal drift was unacceptable >> and the crystal was the first order contributor. The oscillator >> otherwise behaved well. >> >> My solution for the whole mess was a lower frequency osc >> and using low order harmonics. The lower frequency crystale proved >> both less fussy to oscilate and more stable in fundemental mode. >> Note: I was interested in sufficient stability to copy SSB at ~1296mhz >> so even a few dozen Hz drift is noticeable.. >> >> Allison >>> >>> >>> >>> >>> nospam@nouce.bellatlantic.net wrote: >>>> On Mon, 28 Aug 2006 05:59:39 GMT, David >>>> wrote: >>>> >>>>> Dave, >>>>> >>>>> I do have EMIRFD but find almost all the circuits are based around rf >>>>> transformers for matching and most of them are low frequency (3MHz etc). >>>> Up to around 200mhz thats not a big issue if properly scaled and the >>>> right ferrite used. >>>> >>>> I've used a lot of ideas from that book at 6 and 2m. The book list >>>> presented is one I'd have suggested and added the venerable handbook >>>> both current and a few older copies. >>>> >>>> Allison >>>> >>>> >>>>> Regards >>>>> >>>>> David >>>>> >>>>> Dave Platt wrote: >>>>>>> Anyone recommend a "decent" book that would cover oscillators, small >>>>>>> signal RF amps and matching techniques sufficiently to enable a novice >>>>>>> to start experimenting with circuits and have enough detail in the text >>>>>>> to tweak the circuits to get them running properly ? >>>>>> "Experimental Methods in RF Design" by Hayward, Campbell, and Larkin, >>>>>> available from the ARRL, would be a good place to start. It's the >>>>>> successor to the classic "Solid-State Design for the Radio Amateur" >>>>>> from back in 1977. >>>>>> >>>>>> If you can find copies of Doug Demaw's "Design notebook" and "QRP >>>>>> notebook", there's some good reading there as well. Not as advanced >>>>>> as "Experimental Methods" but perhaps a bit more accessible. >>>>>> >>>>>> Buying a bunch of back issues of QRPp might also be helpful. In a lot >>>>>> of the articles which discuss QRP receiver and transmitters, the >>>>>> authors go into detail about their own particular circuit preferences, >>>>>> tweaks, construction and debugging techniques, etc. >>>>>> >>>>>> For a slightly deeper background, I'd recommend "Troubleshooting >>>>>> Analog Circuits" by Robert Pease. It's not specific to RF but is full >>>>>> of useful tricks and ideas. >>>>>> >> Article: 98461 of rec.radio.amateur.homebrew From: Hamateur Subject: Re: Beginner Radio w/o using air variable cap??? Date: Tue, 29 Aug 2006 13:34:47 -0000 Message-ID: <12f8gjn37mpsh9f@corp.supernews.com> References: <1156801375.566432.201790@m73g2000cwd.googlegroups.com> SparkySKO wrote: > > [Basically this says, are there any practical alternatives to an air > variable capacitor that a beginner can use in building his first > receiver radio?] This homebrew 10-600pF book-shaped air variable has knob tuning: http://www.leradiodisophie.it/CV-libro.html Wind a simple coil, add a diode and audio amplification - see what you can hear. Article: 98462 of rec.radio.amateur.homebrew From: "Chas" References: <8Y-dnQuvbIz2GHLZnZ2dnUVZ_uydnZ2d@comcast.com> Subject: Re: radiomart descriptions Date: Tue, 29 Aug 2006 09:31:46 -0500 Message-ID: <1pGdnVp-eZwh0mnZnZ2dnUVZ_qudnZ2d@bright.net> It's the lying that bothers most of us, I bought a radio from him and it smoked when I plugged it in, upon examination, I found it was NO WHERE NEAR what he described, he used photos that didn't show the imperfections and outright lied about the ownership. I know several people who have sold gear to him (using his gottahaveit1995 name) only to see radio-mart sell it a week later, claiming it came from his personal collection and had owned it for years!! Then he lies about the condition of it, not to mention that he shill bids on his gear using the above mentioned gottahaveit1995 name. This asshole needs to be run off ebay, because of how he screws unsuspecting bidders!! "Wesleywoo-woo" wrote in message news:bac77$44f04f82$d1cc790d$30393@snip.allthenewsgroups.com... >I have a better idea Mike. If you don't like the guy re-selling > things he bought at estate sales and other places, simply ignore him. > It's just that simple. Go to another Deli and get your Cornbeef on Rye > at another store. Life's too short to worry about ham radio dealers > that's fer damm sure! :) > > > "mike maghakian" wrote in message > news:8Y-dnQuvbIz2GHLZnZ2dnUVZ_uydnZ2d@comcast.com... >> look at this auction: >> > http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=ADME:B:WNA:US:112&item=110023382429&id= >> >> the seller said he bought it in a radio mart acution and gives the > number. >> radio mart said it was "stunning" and "excellent" >> the seller is now noting all the problems if you read the question > section. >> >> for those of you considering a radiomart auction. consider that he thinks >> telling lies is standard operating procedure. >> >> > Article: 98463 of rec.radio.amateur.homebrew From: "SparkySKO" Subject: Re: Beginner Radio w/o using air variable cap??? Date: 29 Aug 2006 09:08:38 -0700 Message-ID: <1156867718.040087.165480@b28g2000cwb.googlegroups.com> References: <1156801375.566432.201790@m73g2000cwd.googlegroups.com> I finally caved in and cannibalized a radio. 8$ at big lots (heck they even had one for 4$, but this one had a bigger 'knob'). Sure enough, a variable cap (plastic spacers in between the plates). Article: 98464 of rec.radio.amateur.homebrew Date: Tue, 29 Aug 2006 09:12:53 -0700 From: PhattyMo Subject: Re: Beginner Radio w/o using air variable cap??? References: <1156801375.566432.201790@m73g2000cwd.googlegroups.com> Message-ID: <44f46781$0$34071$815e3792@news.qwest.net> SparkySKO wrote: > Hello All, > > [Basically this says, are there any practical alternatives to an air > variable capacitor that a beginner can use in building his first > receiver radio?] > > I'm interested in getting my feet wet in building a receiver, but don't > want to buy a 'kit'. I'd like to build a radio that has a knob I can > somewhat tune it with. I've been really looking at regenerative radios > and superheterodynes, although a simple radio is more important than > how well it really performs. > > One common theme in almost every 'simple' radio design I can find, is > that they *ALL* use Air variable capacitors. While I'm sure these were > everywhere 20 years ago, going to every major electronics supply house > in Portland, Oregon has yielded me only with small trimmer capacitors, > which AFAIK, will not do for a 'tuner'. Oh, A local! Okay,I'mma spill the beans,and 'leak' my hidden treasure trove.. Check out "R5D3 Electronic Surplus" out in Milwaukie,off of Johnson Creek road. He's got *tons* of tubes,and lots of other useful parts for cheap. Got a couple bins/boxes full of variable caps and all that stuff. Bob's a cool guy. Tell him "that young punk" sent ya. ;-) >I'm aware I can order online > for about 10-20$ and purchase an air variable, but I'd like to see if > any of you have any suggestions on what might work as an alternative? > > Varactor diode seemed like a neat idea, although I guess they suffer > from temperature fading. Would this make it impratical for a shortwave > or AM receiver? Can you even make a regenerative radio out of a > varactor? (Actually, I'll try ghetto rigging a red LED for a varactor, > since I don't really care about it being nicely linear, I just want > something with a knob that does something!). > > Can anyone recommend any type of reasonably simple radio (simple mostly > as in reasonably low parts count, i don't need an LCD readout) that > could possibly be done with parts that can be had at a reasonably > stocked electronics store. (Much more inventory than Fry's). A knob is > important, I don't want to build one of those ghetto radios with the > coil and a metal bead that I slide along the coil to 'tune' it. Any > other way to use a potentiometer to tune a radio? > Article: 98465 of rec.radio.amateur.homebrew From: "Christopher Bucca" References: <1135568602.102362.228660@g14g2000cwa.googlegroups.com> Subject: Re: Harry E. Landsberg, Jr., CIA Maltese Falcon: Kennedy assassination, IRAN/CONTRA, UFO's Message-ID: Date: Tue, 29 Aug 2006 18:31:11 GMT Could someone please chlorinate her end of the gene pool, PLEASE?? "Laura" wrote in message news:1135568602.102362.228660@g14g2000cwa.googlegroups.com... > Harry E. Landsberg, Jr., CIA Maltese Falcon: Kennedy assassination, > IRAN/CONTRA, UFO's > > My late father, Harry E. Landsberg, Jr. is apparently one of the 35 CIA > Officers memorialized on the north wall of the Original Headquarters > Building lobby whose "names ... must remain secret, even in death." > > Please see: > > http://www.angelfire.com/journal2/landsbergphotos2/maltese_falcon_search_terms_maltese_falcon_cia_dot_gov.jpg > > taking note of the search terms "maltese+falcon." > > Then: > > http://www.angelfire.com/journal2/landsbergphotos2/maltese_falcon_cia_dot_gov_memorial_wall.jpg > > and > > http://www.angelfire.com/journal2/landsbergphotos2/maltese_falcon_cia_dot_gov_memorial_wall_2.jpg > > ---- > > I was discredited as being mentally ill in 1981 and again in 1985. As > a result I was motivated to research family matters. > > In 2004 I learned that my husband, Richard Hanning, Jr., was a > Marine/covert operator assigned to me. We met in 1985 and I knew I was > a target when I met him. I just didn't know I was his target. > > We are divorced. My life has been in danger and I have been revealing > information about my family and their associates as a result. > > Please see: > > "Harry E. Landsberg, Jr. -- resemblance to man in photo with Specter" > http://home.earthlink.net/~lhann10243/index.html > > and > > "IRAN/CONTRA: Fleming O. Landsberg, Fleming Landsberg, U.S. Ordinance > [sic] Inc." > http://home.earthlink.net/~lhann10243/id85.html > > and > > "Landsbergs and Maddens -- Mirror" (UFO's) > http://www.angelfire.com/journal2/landsbergphotos/Landsbergs_and_Maddens_mirror.html > > ---- > > I am a survivor of satanic ritual abuse and mind control. > > Please see: > > "The Love Game" > http://home.earthlink.net/~sammark4/id2.html > > and > > "Scars and other signs of mind control" > http://home.earthlink.net/~sammark4/id5.html > > ---- > > My legal mother, Donna Jean Volkmer Landsberg, worked as secretary to > the Undersecretary of the Navy in the 1940's, likely James Forrestal. > > He died under mysterious circumstances. Please see: > > "The Death of James Forrestal" by Richard M. Dolan > http://keyholepublishing.com/Death%20of%20James%20Forrestal.htm > > ---- > > I had a vision of Donna as a three-headed bird (black heads.) > > I was searching for photos of Vanessa Redgrave and found this photo > which was similar to the bird in my vision: > > http://www.angelfire.com/journal2/landsbergphotos2/donnas_bird_head_more_like_this.jpg > > Then searching on "Maltese Falcon" I came across "The Virtual Tour of > the CIA:" > > http://images.google.com/imgres?imgurl=http://www.cia.gov/cia/information/ > tour/83stars_lg.jpg&imgrefurl=http://www.cia.gov/cia/information/tour/ > stars.html&h=465&w=600&sz=184&tbnid=fQ8WESE-YHkpWM:&tbnh=103&tbnw > =133&hl=en&start=130&prev=/images%3Fq%3D%2522maltese%2Bfalcon > %2522%26start%3D120%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DN > > or > > http://www.cia.gov/cia/information/tour/stars.html > > There is no mention of the words "Maltese Falcon" on the page. > > ---- > > There was a Divine Intervention in late 2003 and I have been protected > as I have been enduring harassment in the astral plane. > > Please see: > > "Mystical Journey" > http://home.earthlink.net/~sammark4/id157.html > > "Mystical Journey -- more" > http://home.earthlink.net/~silent_no_more99/id41.html > > "Mystical Journey -- more ii" > http://home.earthlink.net/~sammark4lhann/id17.html > > "Mystical Journey -- more iii" > http://home.earthlink.net/~twainablelhann/id17.html > > and > > "To My Friend" > http://home.earthlink.net/~sammark4/id214.html > > "To My Friend -- more" > http://home.earthlink.net/~sammark4lhann/id33.html > > "To My Friend -- more ii" > http://home.earthlink.net/~twainablelhann/id12.html > > "To My Friend -- more iii" > http://home.earthlink.net/~twainable2lhann/id7.html > > ---- > > Laura Landsberg > 305 Linden St., Apt. B > Fond du Lac, WI 54935 > (920) 922-2599 > Article: 98466 of rec.radio.amateur.homebrew From: David Subject: Re: Book recommendation please References: <_1uIg.19044$rP1.12765@news-server.bigpond.net.au> <12f4uvk56v3l96c@corp.supernews.com> <28LIg.19507$rP1.18962@news-server.bigpond.net.au> Message-ID: Date: Tue, 29 Aug 2006 20:41:09 GMT Thanks for the information. The book example uses a 5th OT 100MHz crystal. My application uses a 7th OT 151 MHz crystal. I suspect the ESR jumps from around 60-70 in the 5th OT to a max. of 120R for the 7th OT. Something I find a little confusing though in in Matthys book at the beginning he explains that in series mode, the lower the impedances driving and loading the crystal - the better as this ensures the crystal has maximum control of the feedback path. But during his explanation of the butler emitter follower, he mentions the load cannot be "too" small and suggests optimal load of 1/2 to 1 x ESR. Can you shed some light on this for me please. I realise another option is to build a 3rd OT oscillator followed by a tripler and filtering but I find when I do this that I have trouble getting rid of harmonics. Also each tank circuit ends up adding lots of cost to the circuit as I usually use a fixed air-wound SMD format coil and SMD trimmer cap and these are expensive. Another option was I could use a PLL as I have a heap of the LMX1602. Then the trouble is that the microcontroller overhead goes.(Having to set frequency each time the system boots). I also looked at other PLL ICs like the motorola devices that can be pre-programmed with pin settings but these seem to be hard to obtain now. Thanks again. I appreciate the time people have taken to consider my questions and provide me with some valuable insight that I have not yet gained from experience. (I suppose that is the power of such a forum as this anyway). regards David nospam@nouce.bellatlantic.net wrote: > On Mon, 28 Aug 2006 23:38:38 GMT, David > wrote: > >> From what I understand so far the bias should should not necessarily be >> the same and the capacitors will not scale as suggested. >> >> The ESR of the crystal would be different for different overtone >> crystals so therefore the bias should change to provide correct >> drive and C to ground on the C-Tap would also need to change. According >> to Matthy the Cap to ground should be 0.5 to 1 x ESR and emitter drive >> impedance less than ESR. Or have I misinterpreted something here ? > > The DC bias would be unchanged. The feedback required may need > to be altered but thats a product of frequency and transistor(or fet) > gain at the target frequency and any change in overtone used. > > In short if the circuit shown uses a 100mhz crystal in a 7th overtone > mode it will scale if a 89mhz 7th overtone crystal is used. Usually > for a narrow range of frequencies like that the ERS varies but not > greatly. This does not cover the difference between good quality > crystal and poor quality crystals, If you going to use poor quality > crystals there may be other issues to investigate as well. > >> I am also unsure of whether the tank should be tuned above or below >> resonance. Rhea's book suggests the tank should be capacitive at Fo >> indicating the tank itself would be tuned above the operating frequency. > > Believe it or not, doesn't matter. You'll build it and then have to > tune it for proper oscillation. At around 100mhz the circuit > parasitics such as coil construction, PC board trace capacitance > and inductance, transistor characteristics, transistor, coil and > capactior lead length are all in the mix. > >> I would like to learn more about the Butler emitter follower crystal >> oscillator. >> >> If I ask the specific questions about this typology and someone gives me >> an answer, where did they obtain this information. Have they learned by >> just playing with the circuit in a hit and miss fashion or have they >> first obtained fundamental information from some text and using what >> they have learnt then played with the circuit. If so, what would this >> text be ? > > Generally I try to avoid high order oscilators(overtone) as stability > and the need for being tuned doesn't suit my needs. > > I've never seen a in depth analysis in any one book. I apply > my EE training plus 30+ years of theory vs what really happens > and go from there. Sometimes being an engineer is really more like > science where you observe and build or search out theory to explain > the observed behavour, or you break out the diddle stick and adjust > it and move on to bigger problems. > >> If Ro = Rsource/(beta+1), is Rsource in the oscillator case of the >> emitter follower Rp of the coil in parallel with the bias resistance >> or does it also include (Rphi+RE) x Beta. Is Beta used here an >> approximation calculate by Ft/F ? > > Thats all first order rule of thumb. However, are you trying to build > one working oscillator or flog it to death? I say that as I've found > it to be both less than an exact science and that accurate to more > than 3 decimal places is excess for operation. For one oscillator > it is both easy and practical to dead bug it and see if it meets > your needs. If you going to build in quantity something using it > that is a whole different set of issues. > > Allison > >> >> >> >> nospam@nouce.bellatlantic.net wrote: >>> On Mon, 28 Aug 2006 13:25:40 GMT, David >>> wrote: >>> >>>> Thanks for the feedback. >>>> >>>> I do not have a ready supply of ferrite cores and do not really want to >>>> wind coils. >>>> I have surface mountable air fixed coils that provide Q > 100 that I >>>> expect should be suitable for most applications and use of trimmer >>>> capacitors. >>>> >>>> The only high frequency crystal oscillator I could find in the EMRFD >>>> (100MHz) is page 4.15 which is a common base butler. I understand these >>>> suffer parasitic effects, the tank is only effective for a limited range >>>> of inductance. The butler emitter follower is offered as a more superior >>>> typology but this circuit is not found in this book. >>>> The circuit values in his example are incorrect as the 25nH inductor in >>>> the tank requires over 100pF to resonate at 100MHz. The circuit shown >>>> has a net capacitance of around 40pF ? >>> Built as described, it works. However the 25nH is an approximation >>> as distributed C and also lead lengths add significantly. Mine tuned >>> with 33ohms substituted for the crystal from 93 to 122mhz. >>> >>>> There is very little design information given with respect to ratio of >>>> the C-Tap or emitter bias. >>> Read the test as the concepts are outlined rather than how to design >>> xyz circuit in cookbook fashon. If you need help, the easy way is >>> to calculate the reactances at the shown frequency and then using >>> those numbers scale for the desired frequency. The bias point would >>> be the same at any frequency for a given transistor and power. >>> >>>> I also have his book "Introduction to Radio Frequency design". This does >>>> go into more depth but is centred mainly around colpitts oscillators >>>> (not good for harmonic crystal oscillators). >>> In general oscillators in the >20mhz range are harmonic or overtone >>> designs and more subject to parasitic effects. I've bult the 100mhz >>> design and it worked fine for me within the limits of the crystal used >>> though after a x4 multiplication the thermal drift was unacceptable >>> and the crystal was the first order contributor. The oscillator >>> otherwise behaved well. >>> >>> My solution for the whole mess was a lower frequency osc >>> and using low order harmonics. The lower frequency crystale proved >>> both less fussy to oscilate and more stable in fundemental mode. >>> Note: I was interested in sufficient stability to copy SSB at ~1296mhz >>> so even a few dozen Hz drift is noticeable.. >>> >>> Allison >>>> >>>> >>>> >>>> nospam@nouce.bellatlantic.net wrote: >>>>> On Mon, 28 Aug 2006 05:59:39 GMT, David >>>>> wrote: >>>>> >>>>>> Dave, >>>>>> >>>>>> I do have EMIRFD but find almost all the circuits are based around rf >>>>>> transformers for matching and most of them are low frequency (3MHz etc). >>>>> Up to around 200mhz thats not a big issue if properly scaled and the >>>>> right ferrite used. >>>>> >>>>> I've used a lot of ideas from that book at 6 and 2m. The book list >>>>> presented is one I'd have suggested and added the venerable handbook >>>>> both current and a few older copies. >>>>> >>>>> Allison >>>>> >>>>> >>>>>> Regards >>>>>> >>>>>> David >>>>>> >>>>>> Dave Platt wrote: >>>>>>>> Anyone recommend a "decent" book that would cover oscillators, small >>>>>>>> signal RF amps and matching techniques sufficiently to enable a novice >>>>>>>> to start experimenting with circuits and have enough detail in the text >>>>>>>> to tweak the circuits to get them running properly ? >>>>>>> "Experimental Methods in RF Design" by Hayward, Campbell, and Larkin, >>>>>>> available from the ARRL, would be a good place to start. It's the >>>>>>> successor to the classic "Solid-State Design for the Radio Amateur" >>>>>>> from back in 1977. >>>>>>> >>>>>>> If you can find copies of Doug Demaw's "Design notebook" and "QRP >>>>>>> notebook", there's some good reading there as well. Not as advanced >>>>>>> as "Experimental Methods" but perhaps a bit more accessible. >>>>>>> >>>>>>> Buying a bunch of back issues of QRPp might also be helpful. In a lot >>>>>>> of the articles which discuss QRP receiver and transmitters, the >>>>>>> authors go into detail about their own particular circuit preferences, >>>>>>> tweaks, construction and debugging techniques, etc. >>>>>>> >>>>>>> For a slightly deeper background, I'd recommend "Troubleshooting >>>>>>> Analog Circuits" by Robert Pease. It's not specific to RF but is full >>>>>>> of useful tricks and ideas. >>>>>>> > Article: 98467 of rec.radio.amateur.homebrew From: "SparkySKO" Subject: Hi-Q Ceramic Caps? Date: 29 Aug 2006 14:57:19 -0700 Message-ID: <1156888639.427999.12080@p79g2000cwp.googlegroups.com> Hello All! Bare with me, I'm a newbie. I'm looking into building the Radio Shack Special http://www.electronics-lab.com/projects/rf/007/ And looking through the parts list, I see that he references using Hi-Q Ceramic Capacitors. This radio is for FM, so 90-110mhz. I have a bunch of normal ceramic capacitors, but no hi-q capacitors. Is there really much of a difference between the two, or am I likely to fail if I don't use them? I'd hate to solder all this onto a board, and risk messing up the board when removing them. Any advice on the difference between them would be helpful. I'm guessing they oscillate better, or at higher frequencies. Article: 98468 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: Book recommendation please Message-ID: References: <_1uIg.19044$rP1.12765@news-server.bigpond.net.au> <12f4uvk56v3l96c@corp.supernews.com> <28LIg.19507$rP1.18962@news-server.bigpond.net.au> Date: Tue, 29 Aug 2006 22:07:05 GMT On Tue, 29 Aug 2006 20:41:09 GMT, David wrote: >Thanks for the information. > >The book example uses a 5th OT 100MHz crystal. My application uses a 7th >OT 151 MHz crystal. > >I suspect the ESR jumps from around 60-70 in the 5th OT to a max. of >120R for the 7th OT. I dont consider that a huge jump, considering the amount of tolereance there is in that kind of thing. >Something I find a little confusing though in in Matthys book at the >beginning he explains that in series mode, the lower the impedances >driving and loading the crystal - the better as this ensures the crystal >has maximum control of the feedback path. if the crystal feedbak path loads the crystal too greatly the problems of mode jumping and poor starting are present. >But during his explanation of the butler emitter follower, he mentions >the load cannot be "too" small and suggests optimal load of 1/2 to 1 x >ESR. Can you shed some light on this for me please. too low the osc will not start (low effective gain) and too high allows for possible mode shifts. >I realise another option is to build a 3rd OT oscillator followed by >a tripler and filtering but I find when I do this that I have trouble >getting rid of harmonics. Also each tank circuit ends up adding lots of >cost to the circuit as I usually use a fixed air-wound SMD format coil >and SMD trimmer cap and these are expensive. I would think using double tuned and properly coupled the undesired harmonics should easily be more than 70db down. Requires some care in layout and grounding. >Another option was I could use a PLL as I have a heap of the LMX1602. >Then the trouble is that the microcontroller overhead goes.(Having to >set frequency each time the system boots). I also looked at other PLL >ICs like the motorola devices that can be pre-programmed with pin >settings but these seem to be hard to obtain now. Those headaches and also sidebands that are not well surpressed if care is not taken make it potentially worse than 3rd OT and tripler. build and test is my suggestion. Allison > > >nospam@nouce.bellatlantic.net wrote: >> On Mon, 28 Aug 2006 23:38:38 GMT, David >> wrote: >> >>> From what I understand so far the bias should should not necessarily be >>> the same and the capacitors will not scale as suggested. >>> >>> The ESR of the crystal would be different for different overtone >>> crystals so therefore the bias should change to provide correct >>> drive and C to ground on the C-Tap would also need to change. According >>> to Matthy the Cap to ground should be 0.5 to 1 x ESR and emitter drive >>> impedance less than ESR. Or have I misinterpreted something here ? >> >> The DC bias would be unchanged. The feedback required may need >> to be altered but thats a product of frequency and transistor(or fet) >> gain at the target frequency and any change in overtone used. >> >> In short if the circuit shown uses a 100mhz crystal in a 7th overtone >> mode it will scale if a 89mhz 7th overtone crystal is used. Usually >> for a narrow range of frequencies like that the ERS varies but not >> greatly. This does not cover the difference between good quality >> crystal and poor quality crystals, If you going to use poor quality >> crystals there may be other issues to investigate as well. >> >>> I am also unsure of whether the tank should be tuned above or below >>> resonance. Rhea's book suggests the tank should be capacitive at Fo >>> indicating the tank itself would be tuned above the operating frequency. >> >> Believe it or not, doesn't matter. You'll build it and then have to >> tune it for proper oscillation. At around 100mhz the circuit >> parasitics such as coil construction, PC board trace capacitance >> and inductance, transistor characteristics, transistor, coil and >> capactior lead length are all in the mix. >> >>> I would like to learn more about the Butler emitter follower crystal >>> oscillator. >>> >>> If I ask the specific questions about this typology and someone gives me >>> an answer, where did they obtain this information. Have they learned by >>> just playing with the circuit in a hit and miss fashion or have they >>> first obtained fundamental information from some text and using what >>> they have learnt then played with the circuit. If so, what would this >>> text be ? >> >> Generally I try to avoid high order oscilators(overtone) as stability >> and the need for being tuned doesn't suit my needs. >> >> I've never seen a in depth analysis in any one book. I apply >> my EE training plus 30+ years of theory vs what really happens >> and go from there. Sometimes being an engineer is really more like >> science where you observe and build or search out theory to explain >> the observed behavour, or you break out the diddle stick and adjust >> it and move on to bigger problems. >> >>> If Ro = Rsource/(beta+1), is Rsource in the oscillator case of the >>> emitter follower Rp of the coil in parallel with the bias resistance >>> or does it also include (Rphi+RE) x Beta. Is Beta used here an >>> approximation calculate by Ft/F ? >> >> Thats all first order rule of thumb. However, are you trying to build >> one working oscillator or flog it to death? I say that as I've found >> it to be both less than an exact science and that accurate to more >> than 3 decimal places is excess for operation. For one oscillator >> it is both easy and practical to dead bug it and see if it meets >> your needs. If you going to build in quantity something using it >> that is a whole different set of issues. >> >> Allison >> >>> >>> >>> >>> nospam@nouce.bellatlantic.net wrote: >>>> On Mon, 28 Aug 2006 13:25:40 GMT, David >>>> wrote: >>>> >>>>> Thanks for the feedback. >>>>> >>>>> I do not have a ready supply of ferrite cores and do not really want to >>>>> wind coils. >>>>> I have surface mountable air fixed coils that provide Q > 100 that I >>>>> expect should be suitable for most applications and use of trimmer >>>>> capacitors. >>>>> >>>>> The only high frequency crystal oscillator I could find in the EMRFD >>>>> (100MHz) is page 4.15 which is a common base butler. I understand these >>>>> suffer parasitic effects, the tank is only effective for a limited range >>>>> of inductance. The butler emitter follower is offered as a more superior >>>>> typology but this circuit is not found in this book. >>>>> The circuit values in his example are incorrect as the 25nH inductor in >>>>> the tank requires over 100pF to resonate at 100MHz. The circuit shown >>>>> has a net capacitance of around 40pF ? >>>> Built as described, it works. However the 25nH is an approximation >>>> as distributed C and also lead lengths add significantly. Mine tuned >>>> with 33ohms substituted for the crystal from 93 to 122mhz. >>>> >>>>> There is very little design information given with respect to ratio of >>>>> the C-Tap or emitter bias. >>>> Read the test as the concepts are outlined rather than how to design >>>> xyz circuit in cookbook fashon. If you need help, the easy way is >>>> to calculate the reactances at the shown frequency and then using >>>> those numbers scale for the desired frequency. The bias point would >>>> be the same at any frequency for a given transistor and power. >>>> >>>>> I also have his book "Introduction to Radio Frequency design". This does >>>>> go into more depth but is centred mainly around colpitts oscillators >>>>> (not good for harmonic crystal oscillators). >>>> In general oscillators in the >20mhz range are harmonic or overtone >>>> designs and more subject to parasitic effects. I've bult the 100mhz >>>> design and it worked fine for me within the limits of the crystal used >>>> though after a x4 multiplication the thermal drift was unacceptable >>>> and the crystal was the first order contributor. The oscillator >>>> otherwise behaved well. >>>> >>>> My solution for the whole mess was a lower frequency osc >>>> and using low order harmonics. The lower frequency crystale proved >>>> both less fussy to oscilate and more stable in fundemental mode. >>>> Note: I was interested in sufficient stability to copy SSB at ~1296mhz >>>> so even a few dozen Hz drift is noticeable.. >>>> >>>> Allison >>>>> >>>>> >>>>> >>>>> nospam@nouce.bellatlantic.net wrote: >>>>>> On Mon, 28 Aug 2006 05:59:39 GMT, David >>>>>> wrote: >>>>>> >>>>>>> Dave, >>>>>>> >>>>>>> I do have EMIRFD but find almost all the circuits are based around rf >>>>>>> transformers for matching and most of them are low frequency (3MHz etc). >>>>>> Up to around 200mhz thats not a big issue if properly scaled and the >>>>>> right ferrite used. >>>>>> >>>>>> I've used a lot of ideas from that book at 6 and 2m. The book list >>>>>> presented is one I'd have suggested and added the venerable handbook >>>>>> both current and a few older copies. >>>>>> >>>>>> Allison >>>>>> >>>>>> >>>>>>> Regards >>>>>>> >>>>>>> David >>>>>>> >>>>>>> Dave Platt wrote: >>>>>>>>> Anyone recommend a "decent" book that would cover oscillators, small >>>>>>>>> signal RF amps and matching techniques sufficiently to enable a novice >>>>>>>>> to start experimenting with circuits and have enough detail in the text >>>>>>>>> to tweak the circuits to get them running properly ? >>>>>>>> "Experimental Methods in RF Design" by Hayward, Campbell, and Larkin, >>>>>>>> available from the ARRL, would be a good place to start. It's the >>>>>>>> successor to the classic "Solid-State Design for the Radio Amateur" >>>>>>>> from back in 1977. >>>>>>>> >>>>>>>> If you can find copies of Doug Demaw's "Design notebook" and "QRP >>>>>>>> notebook", there's some good reading there as well. Not as advanced >>>>>>>> as "Experimental Methods" but perhaps a bit more accessible. >>>>>>>> >>>>>>>> Buying a bunch of back issues of QRPp might also be helpful. In a lot >>>>>>>> of the articles which discuss QRP receiver and transmitters, the >>>>>>>> authors go into detail about their own particular circuit preferences, >>>>>>>> tweaks, construction and debugging techniques, etc. >>>>>>>> >>>>>>>> For a slightly deeper background, I'd recommend "Troubleshooting >>>>>>>> Analog Circuits" by Robert Pease. It's not specific to RF but is full >>>>>>>> of useful tricks and ideas. >>>>>>>> >> Article: 98469 of rec.radio.amateur.homebrew From: Wes Stewart Subject: Re: Hi-Q Ceramic Caps? Date: Tue, 29 Aug 2006 15:33:29 -0700 Message-ID: References: <1156888639.427999.12080@p79g2000cwp.googlegroups.com> On 29 Aug 2006 14:57:19 -0700, "SparkySKO" wrote: >Hello All! > >Bare with me, I'm a newbie. Only if you're female. Article: 98470 of rec.radio.amateur.homebrew From: "SparkySKO" Subject: Re: Hi-Q Ceramic Caps? Date: 29 Aug 2006 16:51:03 -0700 Message-ID: <1156895462.934525.236310@h48g2000cwc.googlegroups.com> References: <1156888639.427999.12080@p79g2000cwp.googlegroups.com> Wes Stewart wrote: > On 29 Aug 2006 14:57:19 -0700, "SparkySKO" > wrote: > > >Hello All! > > > >Bare with me, I'm a newbie. > > Only if you're female. Okay okay, bear with me.. Sorry, I went to a public school. Article: 98471 of rec.radio.amateur.homebrew From: Roy Lewallen Subject: Re: Hi-Q Ceramic Caps? Date: Tue, 29 Aug 2006 18:39:07 -0700 Message-ID: <12f9r1uhrlah72e@corp.supernews.com> References: <1156888639.427999.12080@p79g2000cwp.googlegroups.com> For the 5 pF and 15 pF capacitors, use only NPO (C0G) ceramic capacitors -- otherwise the frequency will drift. For just receiving FM broadcast, you *might* get by with "stable" ceramic caps, like X7R, since the signals are broad. But try to get NPO if you can. For the other capacitors, use ones which are physically small. Multilayer ceramic capacitors are smaller than disks. Get some solder wick, which is a wire braid soaked with flux. To remove components, first remove the solder with the wick, then you can pull the components out without damaging the board. Any beginner's board that won't tolerate removal of parts is crap and shouldn't be on the market. Roy Lewallen, W7EL SparkySKO wrote: > Hello All! > > Bare with me, I'm a newbie. > > I'm looking into building the Radio Shack Special > > http://www.electronics-lab.com/projects/rf/007/ > > And looking through the parts list, I see that he references using Hi-Q > Ceramic Capacitors. This radio is for FM, so 90-110mhz. > > I have a bunch of normal ceramic capacitors, but no hi-q capacitors. Is > there really much of a difference between the two, or am I likely to > fail if I don't use them? I'd hate to solder all this onto a board, and > risk messing up the board when removing them. > > Any advice on the difference between them would be helpful. I'm > guessing they oscillate better, or at higher frequencies. > Article: 98472 of rec.radio.amateur.homebrew From: Roy Lewallen Subject: Re: Beginner Radio w/o using air variable cap??? Date: Tue, 29 Aug 2006 21:40:51 -0700 Message-ID: <12fa5mm8b60as66@corp.supernews.com> References: <1156801375.566432.201790@m73g2000cwd.googlegroups.com> xpyttl wrote: > . . . > Varactors do have some temperature coefficient, and they are often coupled > with toroid inductors, which also have some considerable temperature > coefficient. Most of the designs you see out there are for CW rigs in the > ham bands, where temperature stability is extremely important. The maze of > capacitors around the varactor are there to balance the temperature > coefficients. Usually there is a polystyrene capacitor which has a > temperature coefficient opposite to the toroid and varactor, but you can > never get exactly the right value for that, so it is a question of getting > the right combination of positive and negative temperature coefficients AND > the right value of capacitance. For AM in the broadcast band, you can > probably come close enough with one or two capacitors. For a rig with a 200 > Hz CW filter at 15 meters, it can be a real bear keeping the frequency to > within the 0.0001% that you need for comfortable operation. > . . . All toroid inductors aren't equal, and neither are capacitors. I routinely build VFOs with no temperature compensation which have about 200 Hz total warmup drift on 40 meters. The trick is to use components which have inherently low temperature coefficients rather than try to make ones with high coefficients compensate each other. Polystyrene capacitors have a fairly high temperature coefficient, but it's in the opposite direction than a typical poor inductor. Sometimes people get lucky and the combination works ok, but often they don't and it doesn't. The other thing you have to do is design your oscillator so that its frequency depends almost solely on the tank components and not the active device. I found that good quality NPO ceramic capacitors have the lowest temperature coefficient of any commonly available parts, and inductors wound on type 6 powdered iron cores were the best. It's the inductor which dominates the drift in my VFOs, and that small amount can easily be compensated if desired by replacing part of the tank C with a capacitor with controlled temperature coefficient. I described these techniques (except for compensation) in more detail in "An Optimized QRP Transceiver", in August 1980 QST. Roy Lewallen, W7EL Article: 98473 of rec.radio.amateur.homebrew From: Roy Lewallen Subject: Re: Beginner Radio w/o using air variable cap??? Date: Tue, 29 Aug 2006 21:48:53 -0700 Message-ID: <12fa65p2cc7pn81@corp.supernews.com> References: <1156801375.566432.201790@m73g2000cwd.googlegroups.com> <1156807432.877350.199500@m73g2000cwd.googlegroups.com> laura halliday wrote: > . . . > I'd try R5D3 first, then see if I could find something worth > cannibalizing at Cascade (note new address) or Wacky > Willy's (lots of junk, but you never know...). Then I'd hit the > various thrift stores and see if I could find an old FM tuner. At Sea-Pac this year I found out that Wacky Willy's has also moved from its long time location across from the Reedville Cafe. > Are there any ham radio swap meets coming up? There's the Salem club swap meet at Rickreall in February, and Sea-Pac at Seaside in June, but no other major local ones I know of. I'm sure that a query on a local repeater would bring full details of any others. > . . . Roy Lewallen, W7EL Article: 98474 of rec.radio.amateur.homebrew Date: Tue, 29 Aug 2006 22:06:26 -0700 From: "H. P. Friedrichs" Subject: Re: Beginner Radio w/o using air variable cap??? References: <1156801375.566432.201790@m73g2000cwd.googlegroups.com> <12f8gjn37mpsh9f@corp.supernews.com> Message-ID: <1f2dnYSIN8hOgWjZnZ2dnUVZ_sGdnZ2d@velocitywest.com> Here's a radio tuner based on a variometer and fixed capacitor. The variometer housing is a CDROM container; the capacitor is built from blank CDROMS. http://www.hpfriedrichs.com/rr-cdrom.htm 73 Pete AC7ZL Hamateur wrote: > SparkySKO wrote: > >>[Basically this says, are there any practical alternatives to an air >>variable capacitor that a beginner can use in building his first >>receiver radio?] > > > This homebrew 10-600pF book-shaped air variable has knob tuning: > http://www.leradiodisophie.it/CV-libro.html > > Wind a simple coil, add a diode and audio amplification - > see what you can hear. > Article: 98475 of rec.radio.amateur.homebrew From: "hamguy1" Subject: looking for service manual for 747 urgent Date: Wed, 30 Aug 2006 17:42:06 +1000 Message-ID: <44f54147$0$18777$afc38c87@news.optusnet.com.au> hi guys , i have a yaesu757gx 1 it has a few little problems the main vfo is off on modes usb lsb as well the tx usb freq is off .i was wondering if anyone could help me out with a free pdf or win rar service manual they have online or in there favourites i need help to align this 747 where it should be originally .thanks in advance ham guy1 nsw australia . Article: 98476 of rec.radio.amateur.homebrew Date: Wed, 30 Aug 2006 10:55:03 +0100 From: Highland Ham Subject: Re: looking for service manual for 747 urgent References: <44f54147$0$18777$afc38c87@news.optusnet.com.au> Message-ID: hamguy1 wrote: > hi guys , i have a yaesu757gx 1 it has a few little problems the main vfo > is off on modes usb lsb as well the tx usb freq is off .i was wondering if > anyone could help me out with a free pdf or win rar service manual they have > online or in there favourites i need help to align this 747 where it should > be originally .thanks in advance ham guy1 nsw australia . > > ======================== You'll find the manual at www.mods.dk Manuals ----> Yaesu -----> Frank GM0CSZ / KN6WH Article: 98477 of rec.radio.amateur.homebrew From: "Alan Holmes" References: <44f54147$0$18777$afc38c87@news.optusnet.com.au> Subject: Re: looking for service manual for 747 urgent Message-ID: Date: Wed, 30 Aug 2006 16:02:37 GMT "Highland Ham" wrote in message news:cqidnfrK5oPq_WjZRVnyqA@pipex.net... > hamguy1 wrote: >> hi guys , i have a yaesu757gx 1 it has a few little problems the main >> vfo is off on modes usb lsb as well the tx usb freq is off .i was >> wondering if anyone could help me out with a free pdf or win rar service >> manual they have online or in there favourites i need help to align this >> 747 where it should be originally .thanks in advance ham guy1 nsw >> australia . > ======================== > You'll find the manual at www.mods.dk Manuals ----> Yaesu -----> What is the point, he obviously didn't bother to read your first post on the subject! > > Frank GM0CSZ / KN6WH Article: 98478 of rec.radio.amateur.homebrew From: "K7ITM" Subject: Re: Hi-Q Ceramic Caps? Date: 30 Aug 2006 11:10:03 -0700 Message-ID: <1156961403.048645.304590@e3g2000cwe.googlegroups.com> References: <1156888639.427999.12080@p79g2000cwp.googlegroups.com> Actually, modern ceramic capacitors generally are pretty high Q, though I wonder if the "Hi-Q" may be a trademarked name. The problem, as Roy suggests, is more likely to be temperature stability, and as he says, the 5pF and 15pF parts in the design are the ones to be careful about. I'd guess you will have a very hard time finding 5pF and 15pF capacitors which are NOT either temperature stable (NPO or C0G type) or controlled coefficient (negative or positive temperature coefficient, typically used to compensate for drift in coils...since a coil typically expands with increased temperature, its inductance goes up, and that can be compensated by a capacitor whose capacitance goes down). The dielectrics which are not stable, like X7R, Y5V and Z5U, are used in high capacitance parts, and looking at a couple manufacturers' data sheets, the smallest value X7R I see is 100pF. If the capacitor is large enough, it may be marked "NPO" or "N220" or something similar to let you know its temperature characteristic. In the RF part of the circuit, especially, keeping lead lengths very short is important. You don't want the part that's supposed to be a capacitor also include a lot of inductance. There are ceramic capacitors which are specially designed for use at UHF and microwave frequencies, and maintain very high Q up into GHz frequencies, but you shouldn't need anything like that. Also, be aware that "5pF" is deprecated: modern parts are much more likely to be in the standard "e12" sequence: 1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2, 10, ... So for the "5pF" you'd use a 4.7pF part (and probably not notice the difference at all). Another note: I notice the instructions you referenced say to use a form for the source coil that's EXACTLY 8mm diameter. I'm confident that if you use one that's 5/16" diameter, you won't notice the difference. In fact, if you use one that's 1/4" diameter and wind it with 32 turns of close-wound 24 AWG enamelled wire, it's very likely to work just as well. You could also use a 2.2uH commercial RF inductor. So maybe you were only baring your soul... Cheers, Tom SparkySKO wrote: > Hello All! > > Bare with me, I'm a newbie. > > I'm looking into building the Radio Shack Special > > http://www.electronics-lab.com/projects/rf/007/ > > And looking through the parts list, I see that he references using Hi-Q > Ceramic Capacitors. This radio is for FM, so 90-110mhz. > > I have a bunch of normal ceramic capacitors, but no hi-q capacitors. Is > there really much of a difference between the two, or am I likely to > fail if I don't use them? I'd hate to solder all this onto a board, and > risk messing up the board when removing them. > > Any advice on the difference between them would be helpful. I'm > guessing they oscillate better, or at higher frequencies. Article: 98479 of rec.radio.amateur.homebrew From: Jim Subject: What would be best way to go from 12 VDC to 12 VAC, 350 Ma, freq not critical? Message-ID: Date: Wed, 30 Aug 2006 14:21:47 -0500 I have a special ozone generating lamp that requires approx 12 VAC at 330 MA (will have to be current limited, as it strikes a gaseous arc and too much current will melt the filaments). I would like to use it in an automotive application. What would you suggest for circuitry to make the conversion? Frequency is not critical, but some form of current limiting is. Jim Article: 98480 of rec.radio.amateur.homebrew Date: Wed, 30 Aug 2006 23:48:32 +0100 From: Samuel Morse Subject: Re: looking for service manual for 747 urgent References: <44f54147$0$18777$afc38c87@news.optusnet.com.au> Message-ID: Alan Holmes wrote: > What is the point, he obviously didn't bother to read your first post on the > subject! What a helpful chap you are! Article: 98481 of rec.radio.amateur.homebrew From: "David Heinsohn" References: <8Y-dnQuvbIz2GHLZnZ2dnUVZ_uydnZ2d@comcast.com> <1pGdnVp-eZwh0mnZnZ2dnUVZ_qudnZ2d@bright.net> Subject: Re: radiomart descriptions Message-ID: Date: Wed, 30 Aug 2006 23:38:29 GMT "not to mention that he shill bids on his gear using the above mentioned gottahaveit1995 name" How do you know this when he makes his auctions private ? Except for X material, why would one want a private auction ? I will agree that he describes the gear much more glowingly than I. He has re-sold 3 of my radios. One went out on a Monday and it was listed Sunday. Dave "Chas" wrote in message news:1pGdnVp-eZwh0mnZnZ2dnUVZ_qudnZ2d@bright.net... > It's the lying that bothers most of us, I bought a radio from him and it > smoked when I plugged it in, upon examination, I found it was NO WHERE NEAR > what he described, he used photos that didn't show the imperfections and > outright lied about the ownership. I know several people who have sold gear > to him (using his gottahaveit1995 name) only to see radio-mart sell it a > week later, claiming it came from his personal collection and had owned it > for years!! Then he lies about the condition of it, not to mention that he > shill bids on his gear using the above mentioned gottahaveit1995 name. This > asshole needs to be run off ebay, because of how he screws unsuspecting > bidders!! > > "Wesleywoo-woo" wrote in message > news:bac77$44f04f82$d1cc790d$30393@snip.allthenewsgroups.com... > >I have a better idea Mike. If you don't like the guy re-selling > > things he bought at estate sales and other places, simply ignore him. > > It's just that simple. Go to another Deli and get your Cornbeef on Rye > > at another store. Life's too short to worry about ham radio dealers > > that's fer damm sure! :) > > > > > > "mike maghakian" wrote in message > > news:8Y-dnQuvbIz2GHLZnZ2dnUVZ_uydnZ2d@comcast.com... > >> look at this auction: > >> > > http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=ADME:B:WNA:US:112&item=110023382429&id= > >> > >> the seller said he bought it in a radio mart acution and gives the > > number. > >> radio mart said it was "stunning" and "excellent" > >> the seller is now noting all the problems if you read the question > > section. > >> > >> for those of you considering a radiomart auction. consider that he thinks > >> telling lies is standard operating procedure. > >> > >> > > > > Article: 98482 of rec.radio.amateur.homebrew From: "kl7r" Subject: Re: Beginner Radio w/o using air variable cap??? Date: 30 Aug 2006 16:45:08 -0700 Message-ID: <1156981508.851910.197150@m79g2000cwm.googlegroups.com> References: <1156801375.566432.201790@m73g2000cwd.googlegroups.com> Check out the Tin Ear receiver: http://www.amqrp.org/kits/tin_ear/TinEar%20Manual.pdf It uses a plastic drinking straw wrapped with wire and a brass screw to make a variable inductor that is part of a permeability tuned VFO. 3 FETs 4 NPNs and 1 PNP 1 toroid It is no longer available as a kit but all the info is there to build one yourself. Article: 98483 of rec.radio.amateur.homebrew From: "Andrew VK3BFA" Subject: Re: looking for service manual for 747 urgent Date: 31 Aug 2006 01:36:19 -0700 Message-ID: <1157013378.229849.252960@h48g2000cwc.googlegroups.com> References: <44f54147$0$18777$afc38c87@news.optusnet.com.au> Samuel Morse wrote: > Alan Holmes wrote: > > > What is the point, he obviously didn't bother to read your first post on the > > subject! > > What a helpful chap you are! Yes, but he has a point - the original person posted this same request on a VK board on the 24th, was pointed towards mods.dk, but still keeps on asking the same question! I think he wants someone to do it for him........and burn a CD, and mail it to him..... Andrew VK3BFA. Article: 98484 of rec.radio.amateur.homebrew From: Jim Subject: Re: What would be best way to go from 12 VDC to 12 VAC, 350 Ma, freq not critical? Message-ID: References: Date: Thu, 31 Aug 2006 06:29:38 -0500 That will do it, thanks, better than tinkering with circuits for a week or two.. On Wed, 30 Aug 2006 23:37:26 GMT, "W3JDR" wrote: >Here's a$15 turnkey solution: > >A $10 12VDC-to-115VAC power inverter: > (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92707) > > + a $5 12VAC wall transformer: >(http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=211271&pa=211271PS) > >. > >Joe >W3JDR > > >"Jim" wrote in message >news:u2pbf2denqf3vov3v7ot5iepg058hp4q2u@4ax.com... >>I have a special ozone generating lamp that requires approx 12 VAC at >> 330 MA (will have to be current limited, as it strikes a gaseous arc >> and too much current will melt the filaments). I would like to use it >> in an automotive application. >> >> What would you suggest for circuitry to make the conversion? >> Frequency is not critical, but some form of current limiting is. >> >> Jim >> > Article: 98485 of rec.radio.amateur.homebrew Date: Thu, 31 Aug 2006 12:56:12 +0100 From: Highland Ham Subject: Re: What would be best way to go from 12 VDC to 12 VAC, 350 Ma, freq References: Message-ID: > That will do it, thanks, better than tinkering with circuits for a > week or two.. ========================== Why not .........after all this is a Newsgroup dedicated to home construction. Frank GM0CSZ / KN6WH Article: 98486 of rec.radio.amateur.homebrew From: "James Thompson" References: Subject: Re: What would be best way to go from 12 VDC to 12 VAC, 350 Ma, freq not critical? Date: Thu, 31 Aug 2006 13:00:40 -0400 Message-ID: "Jim" wrote in message news:rvhdf21n3b423bd3b35hkvc2fkbkvd7kci@4ax.com... > That will do it, thanks, better than tinkering with circuits for a > week or two.. > > > > On Wed, 30 Aug 2006 23:37:26 GMT, "W3JDR" wrote: > >>Here's a$15 turnkey solution: >> >>A $10 12VDC-to-115VAC power inverter: >> (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92707) >> >> + a $5 12VAC wall transformer: >>(http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=211271&pa=211271PS) >> >>. >> >>Joe >>W3JDR >> >> >>"Jim" wrote in message >>news:u2pbf2denqf3vov3v7ot5iepg058hp4q2u@4ax.com... >>>I have a special ozone generating lamp that requires approx 12 VAC at >>> 330 MA (will have to be current limited, as it strikes a gaseous arc >>> and too much current will melt the filaments). I would like to use it >>> in an automotive application. >>> >>> What would you suggest for circuitry to make the conversion? >>> Frequency is not critical, but some form of current limiting is. >>> >>> Jim >>> >> > Adding ozone to the intake huh? Carefull not to have any gas leak around the carb. I would like more details myself you this, like how to control the amount of ozone to the gas mix etc. Article: 98487 of rec.radio.amateur.homebrew From: "shashwat" Subject: how can I use 74ls192 as 74ls190 ???? Date: 31 Aug 2006 10:16:29 -0700 Message-ID: <1157044589.480926.136950@i42g2000cwa.googlegroups.com> I am building this project where I have to use presettable BCD up down counter 74ls192 but that IC is not available in my country... Instead 74LS190 is available.. How can I configure it to work the same???? I am >from a small asian country, NEPAL... Can anyone help me out??? the circuit I am building is the watchman watcher which uses this counter to count how many times the watchman has missed the call... its at http://electronicsforu.com/electronicsforu/lab/ at no.. 54 .. don't hesitate to help me.. its my 2 credit project.. Article: 98488 of rec.radio.amateur.homebrew From: "K7ITM" Subject: Re: how can I use 74ls192 as 74ls190 ???? Date: 31 Aug 2006 10:58:42 -0700 Message-ID: <1157047122.047611.197990@m79g2000cwm.googlegroups.com> References: <1157044589.480926.136950@i42g2000cwa.googlegroups.com> It looks like there are two problems. One is that you don't have a "clear" input on the 74LS190, and the "clear" on the 74LS192 is used in the circuit. But you can use the "load" input, with the A,B,C,D inputs set to zero to accomplish the same thing. Be sure to think about whether the clear takes place when the input is high or low, and whether the load input behaves the same way. The other problem, of course, is that the '190 uses a single clock input, and an UP/DOWN selection, instead of separate UP and DOWN clocks. Since this is apparently a school project, you should expect to do a little thinking, and then you will learn more. Try to think of a very simple logic circuit, which has two inputs (up clock and down clock) and two outputs (up/down, and clock) that will accomplish what you need. One thing to be careful about: how long before the clock signal comes must the up/down input on the 74LS190 be stable? That is, if the clock comes just when the up/down signal is changing, the 74LS190 may get confused. "Do I count up, or do I count down?" So you want to make sure the clock comes only after the up/down is stable. What do you do if an UP clock comes at the same time as a DOWN clock? Should that ever happen in the circuit you are building? COULD it ever happen? If you think about all this, and still have questions, please post again. Most people here won't want to just give you the answer, but will want you to think about it yourself. We are quite willing to give you ideas to get you started thinking, but it's from the thinking that you will really learn. Cheers, Tom shashwat wrote: > I am building this project where I have to use presettable BCD up down > counter 74ls192 but that IC is not available in my country... Instead > 74LS190 is available.. How can I configure it to work the same???? I am > from a small asian country, NEPAL... Can anyone help me out??? the > circuit I am building is the watchman watcher which uses this counter > to count how many times the watchman has missed the call... its at > http://electronicsforu.com/electronicsforu/lab/ at no.. 54 .. don't > hesitate to help me.. its my 2 credit project.. Article: 98489 of rec.radio.amateur.homebrew From: "MarkAren" Subject: Contemporary HV Rectification Date: 31 Aug 2006 12:02:54 -0700 Message-ID: <1157050974.453969.142090@74g2000cwt.googlegroups.com> Hi Guys, I am just about to start on a 2kV supply for a 4CX250 amp. I have a 750VA 1500V transformer and a couple of 15uF 7.5kV caps. In the full wave rectifier department I seem to have a few options: 1) A bridge of Microwave oven rectifiers like the NTE517, 15kV PIV, 550mA avg, 200A peak surge This is by far the simplest and has the same surge capability and 500ma / 1500V is in the same ball park as the 750VA transformer rating. I assume that a small capacitor across each of the 4 devices would be wise -- any suggestions of value. 2) A string of 3 or 4 1N4508 rectifiers, 3-4kV PIV, 3A avg, 200A peak surge The standard topology for this seems to be voltage equalizing resistors across each rectifier along with a transient absorbing cap - maybe 10nF. I am sure I have seen some comments that the resistors may reduce reliability (short of using MELF, most metal film resistors seem to be rated at 300-500v). Are their other easily available higher voltage parts ? Finally a 1500V sine wave has a peak of 2100V, so 3 x 1kV rectifiers is never going to approach the total avalanche voltage, so why bother with the balancing resistors? Sure, the caps have a more balanced voltage across them if the resistors are included... This design involves 12 x (rectifier + resistor + cap) which is starting to take up some PCB space where some well insulated posts are all that is required to support 4 microwave oven rectifiers. All comments appreciated, Thanks, Mark Article: 98490 of rec.radio.amateur.homebrew From: "Chas" References: <8Y-dnQuvbIz2GHLZnZ2dnUVZ_uydnZ2d@comcast.com> <1pGdnVp-eZwh0mnZnZ2dnUVZ_qudnZ2d@bright.net> Subject: Re: radiomart descriptions Date: Thu, 31 Aug 2006 15:28:02 -0500 Message-ID: <9-ydna8LspfC22rZnZ2dnUVZ_oydnZ2d@bright.net> Because before his auctions went "Private", you could see "gottahaveit1995 bidding on numerous things of his. Ebays use of "Private" auctions mystifies me, it only serves to protect questionable dealers, anyone else have more insight? "David Heinsohn" wrote in message news:VjpJg.6982$q63.4842@newssvr13.news.prodigy.com... > "not to mention that he > shill bids on his gear using the above mentioned gottahaveit1995 name" > > How do you know this when he makes his auctions private ? Except for X > material, why would one want a private auction ? > > I will agree that he describes the gear much more glowingly than I. He has > re-sold 3 of my radios. One went out on a Monday and it was listed Sunday. > > Dave > > "Chas" wrote in message > news:1pGdnVp-eZwh0mnZnZ2dnUVZ_qudnZ2d@bright.net... >> It's the lying that bothers most of us, I bought a radio from him and it >> smoked when I plugged it in, upon examination, I found it was NO WHERE > NEAR >> what he described, he used photos that didn't show the imperfections and >> outright lied about the ownership. I know several people who have sold > gear >> to him (using his gottahaveit1995 name) only to see radio-mart sell it a >> week later, claiming it came from his personal collection and had owned >> it >> for years!! Then he lies about the condition of it, not to mention that >> he >> shill bids on his gear using the above mentioned gottahaveit1995 name. > This >> asshole needs to be run off ebay, because of how he screws unsuspecting >> bidders!! >> >> "Wesleywoo-woo" wrote in message >> news:bac77$44f04f82$d1cc790d$30393@snip.allthenewsgroups.com... >> >I have a better idea Mike. If you don't like the guy re-selling >> > things he bought at estate sales and other places, simply ignore him. >> > It's just that simple. Go to another Deli and get your Cornbeef on Rye >> > at another store. Life's too short to worry about ham radio dealers >> > that's fer damm sure! :) >> > >> > >> > "mike maghakian" wrote in message >> > news:8Y-dnQuvbIz2GHLZnZ2dnUVZ_uydnZ2d@comcast.com... >> >> look at this auction: >> >> >> > > http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=ADME:B:WNA:US:112&item=110023382429&id= >> >> >> >> the seller said he bought it in a radio mart acution and gives the >> > number. >> >> radio mart said it was "stunning" and "excellent" >> >> the seller is now noting all the problems if you read the question >> > section. >> >> >> >> for those of you considering a radiomart auction. consider that he > thinks >> >> telling lies is standard operating procedure. >> >> >> >> >> > >> >> > > Article: 98491 of rec.radio.amateur.homebrew From: "Chas" References: <8Y-dnQuvbIz2GHLZnZ2dnUVZ_uydnZ2d@comcast.com> <1pGdnVp-eZwh0mnZnZ2dnUVZ_qudnZ2d@bright.net> Subject: Re: radiomart descriptions Date: Thu, 31 Aug 2006 15:28:44 -0500 Message-ID: <9-ydna4LspfC22rZnZ2dnUVZ_oydnZ2d@bright.net> Because before his auctions went "Private", you could see "gottahaveit1995 bidding on numerous things of his. Ebays use of "Private" auctions mystifies me, it only serves to protect questionable dealers, anyone else have more insight? "David Heinsohn" wrote in message news:VjpJg.6982$q63.4842@newssvr13.news.prodigy.com... > "not to mention that he > shill bids on his gear using the above mentioned gottahaveit1995 name" > > How do you know this when he makes his auctions private ? Except for X > material, why would one want a private auction ? > > I will agree that he describes the gear much more glowingly than I. He has > re-sold 3 of my radios. One went out on a Monday and it was listed Sunday. > > Dave > > "Chas" wrote in message > news:1pGdnVp-eZwh0mnZnZ2dnUVZ_qudnZ2d@bright.net... >> It's the lying that bothers most of us, I bought a radio from him and it >> smoked when I plugged it in, upon examination, I found it was NO WHERE > NEAR >> what he described, he used photos that didn't show the imperfections and >> outright lied about the ownership. I know several people who have sold > gear >> to him (using his gottahaveit1995 name) only to see radio-mart sell it a >> week later, claiming it came from his personal collection and had owned >> it >> for years!! Then he lies about the condition of it, not to mention that >> he >> shill bids on his gear using the above mentioned gottahaveit1995 name. > This >> asshole needs to be run off ebay, because of how he screws unsuspecting >> bidders!! >> >> "Wesleywoo-woo" wrote in message >> news:bac77$44f04f82$d1cc790d$30393@snip.allthenewsgroups.com... >> >I have a better idea Mike. If you don't like the guy re-selling >> > things he bought at estate sales and other places, simply ignore him. >> > It's just that simple. Go to another Deli and get your Cornbeef on Rye >> > at another store. Life's too short to worry about ham radio dealers >> > that's fer damm sure! :) >> > >> > >> > "mike maghakian" wrote in message >> > news:8Y-dnQuvbIz2GHLZnZ2dnUVZ_uydnZ2d@comcast.com... >> >> look at this auction: >> >> >> > > http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=ADME:B:WNA:US:112&item=110023382429&id= >> >> >> >> the seller said he bought it in a radio mart acution and gives the >> > number. >> >> radio mart said it was "stunning" and "excellent" >> >> the seller is now noting all the problems if you read the question >> > section. >> >> >> >> for those of you considering a radiomart auction. consider that he > thinks >> >> telling lies is standard operating procedure. >> >> >> >> >> > >> >> > > Article: 98492 of rec.radio.amateur.homebrew From: "Mike" Subject: Re: radiomart descriptions Date: Thu, 31 Aug 2006 16:57:06 -0400 Message-ID: <12fej93b8d99jc5@news.supernews.com> References: <8Y-dnQuvbIz2GHLZnZ2dnUVZ_uydnZ2d@comcast.com> <1pGdnVp-eZwh0mnZnZ2dnUVZ_qudnZ2d@bright.net> <9-ydna4LspfC22rZnZ2dnUVZ_oydnZ2d@bright.net> "Chas" wrote in message news:9-ydna4LspfC22rZnZ2dnUVZ_oydnZ2d@bright.net... > Because before his auctions went "Private", you could see "gottahaveit1995 > bidding on numerous things of his. Ebays use of "Private" auctions > mystifies > me, it only serves to protect questionable dealers, anyone else have more > insight? The purpose of Private auctions is just that - private. As in not public. For example, where I work, we have a yearly "sell off some old computers to the employees" thing. We have used eBay private auctions for this. Only our employees can bid - not the general public. Mike Article: 98493 of rec.radio.amateur.homebrew From: jgboyles@aol.com Subject: Re: Contemporary HV Rectification Date: 31 Aug 2006 16:29:43 -0700 Message-ID: <1157066982.987471.19870@i42g2000cwa.googlegroups.com> References: <1157050974.453969.142090@74g2000cwt.googlegroups.com> MarkAren wrote: > Hi Guys, > > I am just about to start on a 2kV supply for a 4CX250 amp. I have a > 750VA 1500V transformer and a couple of 15uF 7.5kV caps. > > In the full wave rectifier department I seem to have a few options: > > 1) A bridge of Microwave oven rectifiers like the NTE517, 15kV PIV, > 550mA avg, 200A peak surge > > This is by far the simplest and has the same surge capability and > 500ma / 1500V is in the same ball park as the 750VA transformer > rating. > > I assume that a small capacitor across each of the 4 devices would be > wise -- any suggestions of value. > > 2) A string of 3 or 4 1N4508 rectifiers, 3-4kV PIV, 3A avg, 200A peak > surge > > The standard topology for this seems to be voltage equalizing > resistors across each rectifier along with a transient absorbing cap - > maybe 10nF. > > I am sure I have seen some comments that the resistors may reduce > reliability (short of using MELF, most metal film resistors seem to be > rated at 300-500v). Are their other easily available higher voltage > parts ? > > Finally a 1500V sine wave has a peak of 2100V, so 3 x 1kV rectifiers > is never going to approach the total avalanche voltage, so why bother > with the balancing resistors? Sure, the caps have a more balanced > voltage across them if the resistors are included... > > This design involves 12 x (rectifier + resistor + cap) which is > starting to take up some PCB space where some well insulated posts > are all that is required to support 4 microwave oven rectifiers. > > All comments appreciated, > > Thanks, > > Mark Mark, The 1N4007 or JE125, NTE125 diodes are 10 cents each in groups of 100. Get a bunch of one or the other, see what you can get at 2kv FWB rectifier, less than 1 amp. Power up surge may be a problem. No equalizing R or C. Should be cheep enough to run several in each leg of the FWB to see what you can get. I seem to remember that the equalizing R and C has been decided not needed. Gary N4AST Article: 98494 of rec.radio.amateur.homebrew From: "g. beat" <@> References: <44f54147$0$18777$afc38c87@news.optusnet.com.au> Subject: Re: looking for service manual for 747 urgent Date: Thu, 31 Aug 2006 19:22:25 -0500 Message-ID: "hamguy1" wrote in message news:44f54147$0$18777$afc38c87@news.optusnet.com.au... > hi guys , i have a yaesu757gx 1 it has a few little problems the main vfo > is off on modes usb lsb as well the tx usb freq is off .i was wondering if > anyone could help me out with a free pdf or win rar service manual they > have online or in there favourites i need help to align this 747 where it > should be originally .thanks in advance ham guy1 nsw australia . Service Manual for the FT-757GX -- download it from here: http://www.eserviceinfo.com/downloadsm/13332/Yaesu_FT757GX.html Check the trimmer capacitors. Article: 98495 of rec.radio.amateur.homebrew From: sailtamarack@yahoo.ca Subject: Using the Virtual Ionosphere Date: 31 Aug 2006 17:28:50 -0700 Message-ID: <1157070530.139182.294000@m73g2000cwd.googlegroups.com> Are you tired of buying or building amateur radio equipment? Perhaps putting up an antenna isn't fun anymore. Maybe straining for DX is taking too much effort. Well don't despair - there is an alternative. You need to consider becoming one of the "next generation" hams. Communicate around the world using your computer and special "radio" software. Traditional VoIP programs like eQSO, Echolink and Skype don't make you feel like a "real ham". You need to take the next step and use the Virtual Ionosphere and the CQ100 Transceiver. Call CQ, twiddle the knobs, send CW and RTTY, use ham lingo and make contacts around the world. However, you will need a ham ticket and $89 (after the trial period) in order to use this next generation "radio". Full details at www.qsonet.com Geez - I hope this isn't a glimpse of the future. I think I'll just keep building stuff and be a "relic" ham Roger Article: 98496 of rec.radio.amateur.homebrew From: "ve2ghi@gmail.com" Subject: MRX-40 modification Date: 31 Aug 2006 17:53:19 -0700 Message-ID: <1157071999.677010.81130@b28g2000cwb.googlegroups.com> Hello OM, I have build the MRX-40 form a kit many years ago. It work fine but ... Now I would like to make a small modification to this receiver. I would like to replace the tuning capacitor with some kind of diode. I manage to add a small potentiometer with the shaft getting outside and I remove the initial capacitor. Now I wonder how and what kind of diode I could use. I dont have also any idea about what to expect in the range of tuning. May be someone else had the same idea Any help is will be greatly appraciate. Happy day 72 de Jean (VE2GHI)