Article: 97445 of rec.radio.amateur.homebrew From: Butch Magee Subject: Re: Thank god for this Date: Fri, 19 May 2006 07:51:52 -0500 Message-ID: <126rfrch57bbgcf@corp.supernews.com> References: <655bg.7359$Go6.5368@trnddc04> Me wrote: > In article <655bg.7359$Go6.5368@trnddc04>, > John - KD5YI wrote: > > >>Gary McIsaac wrote: >> >>>Hi everyone >>> >>>Just a quick message, does anyone actually read this news thing if so I >>>would be glad to know why. >>>Is there anyone out there? >>> >>>Thanks >>> >>>Gary >>> >>> >> >> >> >>No. Nobody is here. > > > Not only that but we really don't care if you read it or not...... > > > Me I heard one of 'em on here a few weeks ago, you can notice them by the odor too, if you don't happen to be watching the screen, but that one wasn't too bad. Havn't seen or smelled one since. They can't read you know, but they sure can figure! Butch Article: 97446 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: Modulation Inductor? Message-ID: References: <1148039109.790739.193550@y43g2000cwc.googlegroups.com> Date: Fri, 19 May 2006 13:34:03 GMT On 19 May 2006 04:45:09 -0700, "Telstar Electronics" wrote: >Where did you get the 30-50 henry inductor figure? > >www.telstar-electronics.com For that style of modulator the coke is in series to feed to the plates of finals. You need enough inductance to get around 5000ohms at 300hz at full current. You can get by with less but the low frequency roll off can be a problem. Allison Article: 97447 of rec.radio.amateur.homebrew From: "Pete Bertini" References: Subject: Re: Modulation Inductor? Message-ID: <1Nobg.67954$IZ2.50975@dukeread07> Date: Fri, 19 May 2006 15:12:53 -0400 "John Ferrell" wrote in message news:ekir62poqal48dp6mbv6si6i423221ilko@4ax.com... >I assume you are talking AM modulation and that you really want plate > modulation. > > Otherwise you are discovering why screen modulation was so popular > with 6146 finals! > > de W8CCW John > I suspect he is talking Heising modulation, which normally is used with a single-ended Class A modulator whose plate is directly tied to the PA plate (the choke is used to provide a high impedance to the filter chokes. But, what I wonder, a 50 watt tube audio amp is very substantial, and is probably running Class B P-P. I don't see how Heising modulation would work in that application. Pete Article: 97448 of rec.radio.amateur.homebrew From: "Pete Bertini" References: Subject: Re: Modulation Inductor? Message-ID: Date: Fri, 19 May 2006 15:14:21 -0400 Tony What you need to do is to find a universal modulation transformer and replace the audio output transformer used on the audio amplifier. That is the most practical solution to your quest. Pete Article: 97449 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: Modulation Inductor? Message-ID: References: <1Nobg.67954$IZ2.50975@dukeread07> Date: Fri, 19 May 2006 22:06:00 GMT On Fri, 19 May 2006 15:12:53 -0400, "Pete Bertini" wrote: > >"John Ferrell" wrote in message >news:ekir62poqal48dp6mbv6si6i423221ilko@4ax.com... >>I assume you are talking AM modulation and that you really want plate >> modulation. >> >> Otherwise you are discovering why screen modulation was so popular >> with 6146 finals! >> >> de W8CCW John >> > >I suspect he is talking Heising modulation, which normally is used >with a single-ended Class A modulator whose plate is directly tied >to the PA plate (the choke is used to provide a high impedance to >the filter chokes. But, what I wonder, a 50 watt tube audio amp is >very substantial, and is probably running Class B P-P. I don't see >how Heising modulation would work in that application. > >Pete Thats one form. The other is to use a huge plate inductor and couple with a cap (usually 8 to 20uf) to the plate side of the inductor. The modulator can be either single ended or PP and the plate side of the Mod amp couples through the cap to the mod inductor. Reason for doing this. At 6146 power level you seeing 600-800V DC power for plates and modulation will take this to over 1200. Those numbers are manageable. For bigger tubes (say a pair of 3-500s) the plate voltage can be 2000V or higher and with modulation peaks hit 4000. By using an inductor the PP transformer is isolated >from the really high volts. Choke with required insulation are/were common in big transmitters for broadcast and HF. However mod transformers that can stand 1000V on one side (say PP plates) and 2-5000V on the other side can be hard to come by. Gets the big DC off stuff even though there are some impressive AC voltages with modulation. The trick for 6146 size amps is a big choke on the final plates DC and a good 8uF 1000V cap and you can then use a tube amp of suitable power if you couple the cap to the plate side of the output transformer. You can even use a solid state amp with a 8ohm to few thousand ohm transformer that doesnt have to stand 600-900V dc. Cheap 8ohm to plate(say 2000ohm) transformer? Try a 6V to 220 control transformer backward or maybe a transformer out of an old (tube before transformerless) TV. Allison Article: 97450 of rec.radio.amateur.homebrew From: "Pete Bertini" References: <1Nobg.67954$IZ2.50975@dukeread07> Subject: Re: Modulation Inductor? Message-ID: Date: Fri, 19 May 2006 19:13:44 -0400 wrote in message news:iefs629eetdc847cl956v36g2lu7hdtvka@4ax.com... > On Fri, 19 May 2006 15:12:53 -0400, "Pete Bertini" > wrote: > >> >>"John Ferrell" wrote in message >>news:ekir62poqal48dp6mbv6si6i423221ilko@4ax.com... >>>I assume you are talking AM modulation and that you really want plate >>> modulation. >>> >>> Otherwise you are discovering why screen modulation was so popular >>> with 6146 finals! >>> >>> de W8CCW John >>> >> >>I suspect he is talking Heising modulation, which normally is used >>with a single-ended Class A modulator whose plate is directly tied >>to the PA plate (the choke is used to provide a high impedance to >>the filter chokes. But, what I wonder, a 50 watt tube audio amp is >>very substantial, and is probably running Class B P-P. I don't see >>how Heising modulation would work in that application. >> >>Pete > > Thats one form. The other is to use a huge plate inductor and couple > with a cap (usually 8 to 20uf) to the plate side of the inductor. > The modulator can be either single ended or PP and the plate side of > the Mod amp couples through the cap to the mod inductor. > > Reason for doing this. At 6146 power level you seeing 600-800V > DC power for plates and modulation will take this to over 1200. > Those numbers are manageable. For bigger tubes (say a pair of > 3-500s) the plate voltage can be 2000V or higher and with modulation > peaks hit 4000. By using an inductor the PP transformer is isolated > from the really high volts. Choke with required insulation are/were > common in big transmitters for broadcast and HF. However mod > transformers that can stand 1000V on one side (say PP plates) and > 2-5000V on the other side can be hard to come by. Gets the big DC off > stuff even though there are some impressive AC voltages with > modulation. > > The trick for 6146 size amps is a big choke on the final plates DC and > a good 8uF 1000V cap and you can then use a tube amp of suitable > power if you couple the cap to the plate side of the output > transformer. You can even use a solid state amp with a 8ohm to few > thousand ohm transformer that doesnt have to stand 600-900V dc. > Cheap 8ohm to plate(say 2000ohm) transformer? Try a 6V to 220 > control transformer backward or maybe a transformer out of an old > (tube before transformerless) TV. > > > Allison Agreed, but the choke must be able to stand the high DC standing current without going into saturation. Also, the choke method somewhat limits the maximum modulation unless a few additional steps are taken. I'd be leary about some of the suggestions regarding the use of pwr. transformer windings to accomplish the task. Pete Article: 97451 of rec.radio.amateur.homebrew From: "Lynn Coffelt" Subject: Re: Modulation Inductor? Date: Fri, 19 May 2006 17:15:29 -0700 Message-ID: References: "Tony Angerame" wrote in message news:W8SdndNbbsVRrvDZRVn-rA@comcast.com... > I've acquired a high power 50 watts plus tube type hifi output > transformer. I'd like to try modulating a pair of 6146's with a hifi > amp. The circuits I see use a modulating inductor in series with the B+ > to the final to keep single ended dc off the transformer secondary. > > Here's the rub. Where do you find a 30-50 henry inductor for 800+ volts? > I was thinking of checking out the secondary of a tv transformer? (Not > many left used to be common whatever happened to those tv's). > > Anyone have any ideas on winding one? Seems to me taking an old > transformer apart and scramble winding as much wire as one can afford > might do the trick? > > Ideas? > > A blast from the past: Oftentimes the voltage rating of chokes was more a limitation of breakdown from conductor/windings to the core or case rather than interwinding breakdown. So........... a quick method of cheating on the rating was to mount the choke on standoff insulators or at least insulating the choke from any metal in the chassis or frame of the RF or modulator deck. Only thing then is to be sure to treat that choke core or case as if it might be at high voltage potential......yikes! Although Choke modulation (or Heising as one respondent mentioned) is "high level" modulation if applied to the RF final plate/s, it takes a lot of tinkering to achieve 100% modulation (balanced, above and below zero). Almost always a compromise in Amateur gear, and some broadcast gear came close, but at great expense. Many will throw rocks at me for this, but "low level" modulation is a huge waste of RF power, and in the good (?) old days, was just another weakly modulated hetrodyne the howling AM section of the bands. OH, OUCH, OWEE, HEY! Old Chief Lynn W7LTQ Article: 97452 of rec.radio.amateur.homebrew From: dplatt@radagast.org (Dave Platt) Subject: Re: 5.0 - 5.5 mHz. VFO Date: Sat, 20 May 2006 02:06:17 -0000 Message-ID: <126sucptkqp1ic2@corp.supernews.com> References: <1148089683.117088.14490@j73g2000cwa.googlegroups.com> In article <1148089683.117088.14490@j73g2000cwa.googlegroups.com>, k9jri wrote: >I am looking for a contruction artical or some other starting point for >a solid state 5 to 5.5 mHz. VFO to use with my PSK-20. Hopefully >somebody can point me to a contruction project, a kit or a source of a >VFO. Buying a copy of "Experimental Methods in RF Design" (the successor text to "Solid-State Design for the Radio Amateur") would be a very good place to start reading. These guys have written down a vast amount of very practical information and experience about how to do this sort of thing well and reliably. http://www.bright.net/~kanga/kanga/KK7B/uvfo.htm is a "universal" VFO kit which you might be able to adapt for your needs. Doug Demaw W1FB had another "universal VFO" design in his "QRP Notebook" (a great book if you can find a copy). You can buy a kit for it (board, semiconductors, air-variable cap, copy of the construction article) for $30 from http://www.danscloseoutsandspecialdeals.com/kitcloseouts.html I've bought stuff from Dan a couple of times and have always been satisfied with what I've received. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! Article: 97453 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: Modulation Inductor? Message-ID: References: <1Nobg.67954$IZ2.50975@dukeread07> Date: Sat, 20 May 2006 02:47:13 GMT On Fri, 19 May 2006 19:13:44 -0400, "Pete Bertini" wrote: > >> The trick for 6146 size amps is a big choke on the final plates DC and >> a good 8uF 1000V cap and you can then use a tube amp of suitable >> power if you couple the cap to the plate side of the output >> transformer. You can even use a solid state amp with a 8ohm to few >> thousand ohm transformer that doesnt have to stand 600-900V dc. >> Cheap 8ohm to plate(say 2000ohm) transformer? Try a 6V to 220 >> control transformer backward or maybe a transformer out of an old >> (tube before transformerless) TV. >> >> >> Allison > >Agreed, but the choke must be able to stand the high DC standing >current without going into saturation. Also, the choke method >somewhat limits the maximum modulation unless a few >additional steps are taken. I'd be leary about some of the >suggestions regarding the use of pwr. transformer windings >to accomplish the task. > >Pete I helped someone do exactly that. Power transformers are usualy rated to stand substantial voltage when you consider the HIPOT testing. They make lousy chokes though for lack of enough wire and easy saturation unless massive. The only mod to the reverse transformer as an impedence matcher was to add a shim to the EI laminations to add an airgap so saturation was less an issue. Worked well and sounded good. Allison Article: 97454 of rec.radio.amateur.homebrew From: "5itu" Subject: Transformer for PA Date: Sat, 20 May 2006 11:50:12 +0200 Message-ID: <446ee646$0$19697$8fcfb975@news.wanadoo.fr> Hello, I'm building the "FARA"amplifier (QST June 2003). Unfortunately, I 'm not able to get the T-3/4 cores, so I wonder whether I couldn't take two ferrite cores used to avoid the RFI made by the wiring of computers ? Obviously, I will try it but I would like to get some advices before... 73 Daniel Article: 97455 of rec.radio.amateur.homebrew From: "Nev" Subject: Direct Conversion Receiver with NPN transistors Date: Sat, 20 May 2006 18:13:44 +0800 Message-ID: <446eebb5_2@news.tm.net.my> Does anyone have any schematic for Direct Conversion receiver that does not use any FETs, Valves or ICs (e.g. NE602) but uses NPN transistors? Article: 97456 of rec.radio.amateur.homebrew From: "amdx" References: <1148089683.117088.14490@j73g2000cwa.googlegroups.com> Subject: Re: 5.0 - 5.5 mHz. VFO Date: Sat, 20 May 2006 06:28:17 -0500 Message-ID: "k9jri" wrote in message news:1148089683.117088.14490@j73g2000cwa.googlegroups.com... > I am looking for a contruction artical or some other starting point for > a solid state 5 to 5.5 mHz. VFO to use with my PSK-20. Hopefully > somebody can point me to a contruction project, a kit or a source of a > VFO. > I think there was an article in QST within the last ten years that described a 5 to 5.5 mhz VFO. Mike Article: 97457 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: Direct Conversion Receiver with NPN transistors Message-ID: References: <446eebb5_2@news.tm.net.my> Date: Sat, 20 May 2006 12:19:05 GMT On Sat, 20 May 2006 18:13:44 +0800, "Nev" wrote: >Does anyone have any schematic for Direct Conversion receiver that does not >use any FETs, Valves or ICs (e.g. NE602) but uses NPN transistors? > Yes the microR1. Circuit is in the EMDRF book. May also be on the web somewhere. Essentially it's a DBM (two cores and 4 diodes) a two transistor amp and a crystal osc (1 transistor). Built it for laughs on a pine block and as DC recievers go, not bad. Allison Article: 97458 of rec.radio.amateur.homebrew From: dplatt@radagast.org (Dave Platt) Subject: Re: Direct Conversion Receiver with NPN transistors Date: Sat, 20 May 2006 16:53:54 -0000 Message-ID: <126uid2h89nv9a5@corp.supernews.com> References: <446eebb5_2@news.tm.net.my> >Does anyone have any schematic for Direct Conversion receiver that does not >use any FETs, Valves or ICs (e.g. NE602) but uses NPN transistors? "Experimental Methods in RF design", section 1.8, page 1.13, has the schematic for a DC receiver which uses NPN transistors throughout most of its design (including the product detector). Tuning is done via a varactor-based VCO - you might be able to substitute a reverse-biased junction in an NPN transistor for the varactor. There are two ICs - an LM7805 voltage regulator (for which you could probably substitute a shunt regulator such as a zener diode or an NPN transistor wired up as a Vbe-multiplier) and an LM386 audio amplifier (for which you could substitute the discrete-NPN audio amp design on the previous page of the book). I'd say there's a good chance you could modify this design so that every single semiconductor in it was an NPN transistor such as a 2N3904 or 2N2222 or a similar jellybean. -- 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: 97459 of rec.radio.amateur.homebrew From: et472@FreeNet.Carleton.CA (Michael Black) Subject: Re: 5.0 - 5.5 mHz. VFO Date: 20 May 2006 18:54:58 GMT Message-ID: References: <1148089683.117088.14490@j73g2000cwa.googlegroups.com> <126sucptkqp1ic2@corp.supernews.com> Tim Wescott (tim@seemywebsite.com) writes: > My 1933 ARRL Handbook does not have a schematic for a 5 to 5.5MHz VFO, > much less a solid state one. > > Receivers that used 5MHz VFOs didn't start appearing until the mid '50s > (judging from my meager collection of handbooks -- I only have eight > spanning '33 to '76), with VFO SSB transmitters appearing about the same > time. > I'm sure that was exageration, but they do have a point. 5MHz VFOs have to be one of the more common items in the magazines and books over the years. Even before 5MHz came along for use with a 9MHz IF, the books and magazines were full of VFOs that could be shifted to 5MHz. There was a period when 6MHz was a common VFO frequency, for use with multiplying VHF transmitters, and those would be even easier to shift to 5MHz than a 3.5 or 7Mhz VFO. If someone is asking about a 5MHz VFO, they've not looked far. Now, the case may be that they are looking for something more specific, but in that case it makes sense to be specific. If someone wants out of the book, yes they won't find a 5MHz vfo in the 1933 Handbook. But, once they go that far back not only will they be tubes, but stability will likely be an issue. 1933 either predates the laws requiring "crystal-like" stability, or such laws were recently passed. Look at the diagrams from that era, and a lot of later concerns in construction haven't come into common place. Michael VE2BVW > Someone who was actually alive at the time, or with a more extensive > collection, may be able to contribute more. > > Scott wrote: > >> I'm pretty sure every issue of the ARRL Handbook ever published has had >> a schematic for just such a critter...haven't got one for several years, >> but they USED to have a design... >> >> Scott >> >> >> >> Dave Platt wrote: >> >>> In article <1148089683.117088.14490@j73g2000cwa.googlegroups.com>, >>> k9jri wrote: >>> >>> >>>> I am looking for a contruction artical or some other starting point for >>>> a solid state 5 to 5.5 mHz. VFO to use with my PSK-20. Hopefully >>>> somebody can point me to a contruction project, a kit or a source of a >>>> VFO. >>> >>> >>> >>> Buying a copy of "Experimental Methods in RF Design" (the successor >>> text to "Solid-State Design for the Radio Amateur") would be a very >>> good place to start reading. These guys have written down a vast >>> amount of very practical information and experience about how to do >>> this sort of thing well and reliably. >>> >>> http://www.bright.net/~kanga/kanga/KK7B/uvfo.htm is a "universal" VFO >>> kit which you might be able to adapt for your needs. >>> >>> Doug Demaw W1FB had another "universal VFO" design in his "QRP >>> Notebook" (a great book if you can find a copy). You can buy a kit >>> for it (board, semiconductors, air-variable cap, copy of the >>> construction article) for $30 from >>> >>> http://www.danscloseoutsandspecialdeals.com/kitcloseouts.html >>> >>> I've bought stuff from Dan a couple of times and have always been >>> satisfied with what I've received. >>> > > > -- > > 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: 97460 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: Direct Conversion Receiver with NPN transistors Message-ID: <53vu625crv1hfjpd6k12bqqu5rki324lju@4ax.com> References: <446eebb5_2@news.tm.net.my> <126uid2h89nv9a5@corp.supernews.com> Date: Sat, 20 May 2006 20:38:33 GMT On Sat, 20 May 2006 16:53:54 -0000, dplatt@radagast.org (Dave Platt) wrote: > >>Does anyone have any schematic for Direct Conversion receiver that does not >>use any FETs, Valves or ICs (e.g. NE602) but uses NPN transistors? > >"Experimental Methods in RF design", section 1.8, page 1.13, has the >schematic for a DC receiver which uses NPN transistors throughout most >of its design (including the product detector). Tuning is done via a >varactor-based VCO - you might be able to substitute a reverse-biased >junction in an NPN transistor for the varactor. > >There are two ICs - an LM7805 voltage regulator (for which you could >probably substitute a shunt regulator such as a zener diode or an NPN >transistor wired up as a Vbe-multiplier) and an LM386 audio amplifier >(for which you could substitute the discrete-NPN audio amp design on >the previous page of the book). > >I'd say there's a good chance you could modify this design so that >every single semiconductor in it was an NPN transistor such as a >2N3904 or 2N2222 or a similar jellybean. Thats a good one too. However section 8 page 8.5 has the MicroR1 and you could change the oscillator from crystal to a VFO and have a very simple but decent DC RX. I've tried that one as I was skeptic and even built it on a pine block as show on page 8.4. It works! the advantage is lower parts count and simple to modify for other bands or adding things like VFO. For laughs I changed the coils for 20m. The result when used with my 6m to 20m converter was a very useable 6m RX! The transistors used are 2n3904s but 2n2222 or just about anything you can find should work. Allison Article: 97461 of rec.radio.amateur.homebrew From: "W3JDR" References: <1148089683.117088.14490@j73g2000cwa.googlegroups.com> Subject: Re: 5.0 - 5.5 mHz. VFO Message-ID: Date: Sat, 20 May 2006 22:09:44 GMT If my memory is correct, the PSK-20 is used for, well... PSK. That being the case, I think you might find it difficult to get adequate frequency stability using a free-running VFO. Since the PSK decoder software automatically gives you about 2KHz of tuning in software, a PLL approach would be quite easy and should produce a clean spectrum if done properly. I think a DDS solution would also be quite good for this application Joe W3JDR "k9jri" wrote in message news:1148089683.117088.14490@j73g2000cwa.googlegroups.com... >I am looking for a contruction artical or some other starting point for > a solid state 5 to 5.5 mHz. VFO to use with my PSK-20. Hopefully > somebody can point me to a contruction project, a kit or a source of a > VFO. > Article: 97462 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: Direct Conversion Receiver with NPN transistors Message-ID: References: <446eebb5_2@news.tm.net.my> <1148167078.424706.191120@j33g2000cwa.googlegroups.com> Date: Sun, 21 May 2006 01:39:29 GMT On 20 May 2006 16:17:58 -0700, sailtamarack@yahoo.ca wrote: >You might want to check out VE7BPO's site for DC receiver ideas. He >has lots of experimental circuits using NPNs and he will respond to >emails if you have any questions. > >http://www.qrp.pops.net/ > >Good luck - Roger > > >Nev wrote: >> Does anyone have any schematic for Direct Conversion receiver that does not >> use any FETs, Valves or ICs (e.g. NE602) but uses NPN transistors? Yes, he has an excellnt site and several really nice designs. Another guy to check out is http://www.k8iqy.com/ he does some really nice transistor designs. Those are superhet but worth looking at as the explanations are good and peices can easily be borrowed for other uses. Allison Article: 97463 of rec.radio.amateur.homebrew From: et472@FreeNet.Carleton.CA (Michael Black) Subject: Re: Direct Conversion Receiver with NPN transistors Date: 21 May 2006 02:25:11 GMT Message-ID: References: <446eebb5_2@news.tm.net.my> "Jim" (kill-spam@no-spam.org) writes: > There was an article in QST many years ago ( late 1960's ??) which was > one of the early direct conversion articles. This one used 88 mH filters, > and a three transistor audio amplifier. It was written by Doug Demaw, if > memory serves, and it is probably the simplest, but useful, direct > conversion design I have ever seen. > But one thing about direct conversion receivers is that it took years before they became good. The basic premise, beating a signal directly down to audio, is as old as the regenerative receiver. ANd of course there were explicit mixer/oscillator type receivers in the decades after that, that all seemed to end in "dyne". IN 1961, QST ran an article, I can't remember if it mentioned "direct conversion", that was direct conversion as we came to know it. A mixer and an oscillator, and if I'm remembering they used two tubes in the mixer for a balanced mixer. Then there's the Hayward article, there was a co-author, in 1968, that actually did make mention of "direct conversion". It used schottkey diodes in a balanced mixer. And that's when they took off. But in the articles afterwards used just about any possible mixer, with varying results. Everyone was trying to get a good direct conversion receiver, but I'm not sure they really understood them. So the focus was on another variation of a well-balanced mixer. It took till 1980, before there was a real change. That's when Roy Lewallen came out with his "optimized QRP transceiver", which featured a terminated mixer. I'm pretty certain that's the first time a DC receiver had a terminated mixer. I can remember the 1974 QST article when terminated mixers for VHF converters were introduced to the amateur world. I really do say that 1980 article of Roy's was the dividing line. Before that, no matter how good the mixer there always seemed to be problems. Then we moved into an area where simplicity wasn't the first consideration for direct conversion, but performance came first. Michael VE2BVW > Granted, getting 88 mH coils is not as easy as it was back then, but all > in all, I think this fits the original request. The radio used NPN > transistors thoughout. > > > > Jim > N6BIU > > > Article: 97464 of rec.radio.amateur.homebrew From: "JC" References: Subject: Re: Modulation Inductor? Message-ID: <0J_bg.13154$fb2.5159@newssvr27.news.prodigy.net> Date: Sun, 21 May 2006 14:22:52 GMT Tony, I did exactly what you are describing. I used a solid state audio amp, and drove a tube type audio output transformer backwards to step up the impedance from 8 ohms to several thousand ohms. I used a 4 uf oil capacitor to couple that across a HV choke that carried the RF final amp plate current. For a choke I used a 125 watt Stancor poly-pedance modulation transformer where I used as much winding on the primary as available. It worked very well. It might be easier to consider cathode modulation, and in this case the transformer turns ratio will be much less, and the HV problem will also be less. Maybe a 110/220 vac to 12vac 5 amp filament transformer will work out here. This is just a guess, but it might work. Cathode modulation is a combination of plate and grid 1 modulation, so the % eff is somewhere between 66% (plate) down to 33% (grid) , and might end up at about 50%. Consider the 220 vct winding where the grid return goes to the CT, and the cathode goes to the top of the 220 v winding, and the bottom of the winding goes to ground. Your turns ratio need may vary, but the concept proposed is workable. Jim WD5JKO "Tony Angerame" wrote in message news:W8SdndNbbsVRrvDZRVn-rA@comcast.com... > I've acquired a high power 50 watts plus tube type hifi output > transformer. I'd like to try modulating a pair of 6146's with a hifi amp. > The circuits I see use a modulating inductor in series with the B+ to the > final to keep single ended dc off the transformer secondary. > > Here's the rub. Where do you find a 30-50 henry inductor for 800+ volts? > I was thinking of checking out the secondary of a tv transformer? (Not > many left used to be common whatever happened to those tv's). > > Anyone have any ideas on winding one? Seems to me taking an old > transformer apart and scramble winding as much wire as one can afford > might do the trick? > > Ideas? > > > Thanks, > > > Tony, > > WA6LZH > Article: 97465 of rec.radio.amateur.homebrew From: Ken Scharf Subject: Re: Direct Conversion Receiver with NPN transistors References: <446eebb5_2@news.tm.net.my> Message-ID: Date: Sun, 21 May 2006 11:18:05 -0400 Michael Black wrote: > "Jim" (kill-spam@no-spam.org) writes: > >> There was an article in QST many years ago ( late 1960's ??) which was >>one of the early direct conversion articles. This one used 88 mH filters, >>and a three transistor audio amplifier. It was written by Doug Demaw, if >>memory serves, and it is probably the simplest, but useful, direct >>conversion design I have ever seen. >> > > But one thing about direct conversion receivers is that it took years before > they became good. > > The basic premise, beating a signal directly down to audio, is as old as > the regenerative receiver. ANd of course there were explicit mixer/oscillator > type receivers in the decades after that, that all seemed to end in "dyne". > > IN 1961, QST ran an article, I can't remember if it mentioned "direct > conversion", that was direct conversion as we came to know it. A mixer > and an oscillator, and if I'm remembering they used two tubes in the mixer > for a balanced mixer. > > Then there's the Hayward article, there was a co-author, in 1968, that > actually did make mention of "direct conversion". It used schottkey > diodes in a balanced mixer. And that's when they took off. > > But in the articles afterwards used just about any possible mixer, > with varying results. Everyone was trying to get a good direct conversion > receiver, but I'm not sure they really understood them. So the focus > was on another variation of a well-balanced mixer. > > It took till 1980, before there was a real change. That's when Roy > Lewallen came out with his "optimized QRP transceiver", which featured > a terminated mixer. I'm pretty certain that's the first time a DC > receiver had a terminated mixer. I can remember the 1974 QST article when > terminated mixers for VHF converters were introduced to the amateur world. > > I really do say that 1980 article of Roy's was the dividing line. Before > that, no matter how good the mixer there always seemed to be problems. Then > we moved into an area where simplicity wasn't the first consideration for > direct conversion, but performance came first. > > Michael VE2BVW > > >> Granted, getting 88 mH coils is not as easy as it was back then, but all >>in all, I think this fits the original request. The radio used NPN >>transistors thoughout. >> >> >> >> Jim >> N6BIU >> >> >> > > > The direct conversion transceiver is what gave TenTec their start. They had a few different models in kit, semi-kit, and assembled formats. QST picked up the craze and there were a number of articles on building these. Detectors were dual gate fets, CA2028's, diode bridges, Mini-Circuit mixer modules, and later IC's with built in vfo's. Back in the 60's, there was an early direct conversion receiver that used two 6SB7Y's in a balanced circuit with a B&W phase splitter run bass-ackwards and an rf phase splitter in the vfo. This was actually a single signal receiver using the idea of a phasing sideband modulator in reverse. Today we'd call it an image-reject mixer. What's old is new again..... Article: 97466 of rec.radio.amateur.homebrew From: Ken Scharf Subject: Re: Transformer for PA References: <446ee646$0$19697$8fcfb975@news.wanadoo.fr> Message-ID: Date: Sun, 21 May 2006 11:21:04 -0400 5itu wrote: > Hello, > > I'm building the "FARA"amplifier (QST June 2003). > Unfortunately, I 'm not able to get the T-3/4 cores, so I wonder whether I > couldn't take two ferrite cores used to avoid the RFI made by the wiring of > computers ? > Obviously, I will try it but I would like to get some advices before... > > 73 Daniel > > Usually, the ferrite cores used for RFI rejection are made of the same stuff as those used in broadband power transformers so it might work. However those cores are split in two for easy application. Glue them together first with a good grade of epoxy keeping the glue layer as thin as possible. The power handling may not be as good as the real McCoy though..... Article: 97467 of rec.radio.amateur.homebrew From: Roy L. Fuchs Subject: Re: FA KEITHLEY 610C ELECTROMETER, PICO AMMETER COULOMB METER Plus Message-ID: References: <8659g.23076$mX1.20976@newsfe2-gui.ntli.net> <-5GdndVPALJIOfrZnZ2dnUVZ_vqdnZ2d@comcast.com> <0rhl629t40if5hih8t7hm85gn5s5h44qei@4ax.com> Date: Sun, 21 May 2006 19:47:24 GMT On Sun, 21 May 2006 11:24:16 -0400, "Ross Mac" Gave us: > >"Roy L. Fuchs" wrote in message >news:0rhl629t40if5hih8t7hm85gn5s5h44qei@4ax.com... >> On Mon, 15 May 2006 19:42:38 -0400, "Ross Mac" >> Gave us: >> >>> >>>"Roy L. Fuchs" wrote in message >>>news:gvof629spp34fho2k68kvv340b0memcg0r@4ax.com... >>>> On Sun, 14 May 2006 17:44:51 -0400, "Ross Mac" >>>> Gave us: >>>> >>>>> >>>>>"Roy L. Fuchs" wrote in message >>>>>news:l70f62pu6h880c700hb0lghjn9moindili@4ax.com... >>>>>> On Fri, 12 May 2006 19:12:04 GMT, Gave us: >>>>>> >>>>>>>FA KEITHLEY >>>>>> >>>>>> You posted to only ONE correct group. The posts in the rest of the >>>>>> groups are all SPAM, asshole. >>>>> >>>>>Wrong again Dimbulb...do your homework..... >>>>> >>>> Not in school, you stupid fucktard. >>> >>>Oh...you must be...you use schoolyard lingo! >> >> You wouldn't know. You're just an old alzheimeristic twit. >> >>>That's the best you can do Hey Dimbulb? >> >> My worst is two orders of magnitude better than your best. >> >>>Wrong and wrong again....what else is new.... >> >> You should stop talking about yourself. >> >>>Big on mouth and small on brains..... >>> >> You're an idiot. That is quite succinct. >> >> This is a text forum, you retarded bastard. There are no mouths >> here, dumbfuck. > >The typical moronic response expected from the likes of you Darkmatter..... > You're an idiot. Article: 97468 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: Direct Conversion Receiver with NPN transistors Message-ID: References: <446eebb5_2@news.tm.net.my> <44udnTFJn8GJIu3ZnZ2dnUVZ_sSdnZ2d@comcast.com> Date: Sun, 21 May 2006 20:54:05 GMT On Sun, 21 May 2006 12:27:12 -0700, "Jim" wrote: >Ken Sharf Wrote: > >>Back in the 60's, there was an early direct conversion receiver that >>used two 6SB7Y's in a balanced circuit with a B&W phase splitter run >>bass-ackwards and an rf phase splitter in the vfo. This was actually >>a single signal receiver using the idea of a phasing sideband modulator >>in reverse. Today we'd call it an image-reject mixer. >> >>What's old is new again..... >> > > I remember that one !! Seems to me, it was in Single Sideband for the >Radio Amateur and I was really tempted to try to build one. > > Actually, I was responding to the original request for a direct conversion >using NPN transistors. There are a lot of designs for direct conversion >rigs, and some of them are excellent. > > Personally, I like the designs by KK7B and if someone wants to try their >hand at it, the Kanga website has some kits available. The R1 while not image reject is by far one of the best DC designs. >http://www.bright.net/~kanga/kanga/KK7B/minir2.htm I currently run the MiniR2 and T2 on 6m and it's a great listening RX and people tell me it's FB TX. > They also carry the R2PRO which has excellent characteristics > >http://www.bright.net/~kanga/kanga/KK7B/r2pro.htm > > I've homebrewed from scratch some direct conversion breadboards over the >years, but these are image reject and would be a good starting point for a >complete transceiver. I've used the MiniR2 as a fixed frequency 20mhz IF with a 4 crystal filter ahead of it for one of the most bullet proof RX I'd every had. With the crystal filter the opposite sideband just wasn't there. Allison Article: 97469 of rec.radio.amateur.homebrew From: Straydog Subject: Hamfest, Georgetown, Delaware, May 27, 2006, 7 am- 5pm Date: Sun, 21 May 2006 19:23:05 -0400 Message-ID: References: <6Zbbg.26026$4H.22143@dukeread03> At Sussex Tech High School, US Route 9 about a mile west of Route 113. Admission free Talk in 147.075 + input more info: n3jvt@yahoo.com w3hrt@arrl.net dsmith@sussex.vt.k12.de.us Also, was mentioned in latest QST Article: 97470 of rec.radio.amateur.homebrew From: "JustMe" References: <446eebb5_2@news.tm.net.my> Subject: Re: Direct Conversion Receiver with NPN transistors Message-ID: Date: Mon, 22 May 2006 00:32:46 GMT Try this link: http://www.phonestack.com/farhan/xcvr1.html "Nev" wrote in message news:446eebb5_2@news.tm.net.my... > Does anyone have any schematic for Direct Conversion receiver that does not > use any FETs, Valves or ICs (e.g. NE602) but uses NPN transistors? > > Article: 97471 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: Direct Conversion Receiver with NPN transistors Message-ID: References: <446eebb5_2@news.tm.net.my> Date: Mon, 22 May 2006 01:54:44 GMT On Mon, 22 May 2006 00:32:46 GMT, "JustMe" wrote: >Try this link: >http://www.phonestack.com/farhan/xcvr1.html > Thats a transceiver of superhet design. An interesting one that I've built for experiment. It is not a Direct Conversion reciever. The request as you've copied said... >"Nev" wrote in message news:446eebb5_2@news.tm.net.my... >> Does anyone have any schematic for Direct Conversion receiver that does >>not use any FETs, Valves or ICs (e.g. NE602) but uses NPN transistors? What part of Direct Conversion was missed? Allison Article: 97472 of rec.radio.amateur.homebrew From: "Dale Parfitt" References: <1148089683.117088.14490@j73g2000cwa.googlegroups.com> Subject: Re: 5.0 - 5.5 mHz. VFO Message-ID: Date: Mon, 22 May 2006 12:39:46 GMT "k9jri" wrote in message news:1148089683.117088.14490@j73g2000cwa.googlegroups.com... >I am looking for a contruction artical or some other starting point for > a solid state 5 to 5.5 mHz. VFO to use with my PSK-20. Hopefully > somebody can point me to a contruction project, a kit or a source of a > VFO. > Google W7ZOI Progressive Receiver or check any ARRL Handbook from 1987-1994. Mine has a worst case 5 minute warmup of +150Hz and stable +/- 20HZ therafter in any 5 minute period. Dale W4OP Article: 97473 of rec.radio.amateur.homebrew From: "Lynn Coffelt" Subject: Re: Modulation Inductor? Date: Sun, 21 May 2006 18:27:52 -0700 Message-ID: References: <9m7172hknjg8iits6h40c4cmdf97h5dmp9@4ax.com> "Gary Schafer" wrote in message news:9m7172hknjg8iits6h40c4cmdf97h5dmp9@4ax.com... > > It looks like AM is really becoming a "lost art". Of all the responses > here, only one or two guy knows what you are talking about. > > The purpose of the choke inductor like you are describing is to keep > the DC off the secondary of the modulation transformer. This allows > the use of a modulation transformer with much less iron, which will > give better low frequency response. If the finals DC current is run > through the modulation transformer, as is commonly done, there needs > to be an air gap in the transformer to keep the core from saturating > from the DC current. The bigger the air gap the less inductance, the > greater amount of DC current it can handle before saturation and the > poorer low frequency response. To increase the inductance with a > larger air gap requires more iron (larger core) to bring the > inductance back up. > > By using a choke and capacitivly coupling the audio from the > modulation transformer to the final plate there is no DC on the > secondary of the modulation transformer to cause saturation. The > modulation transformer then can be any audio transformer. It doesn't > need an air gap. The transformer can have much less iron in it for the > same amount of inductance as one with an air gap. Very good low > frequency response can be had this way. > > By the way the screens of the final tubes need to be modulated along > with the plates too. The easy way is to supply the screens through a > dropping resistor from the top of the choke, the same point that feeds > the plates. > > THIS IS NOT HEISING MODULATION. It is regular old plate modulation > just like you would do with a conventional modulation transformer. > > Yes power transformers can be used quite successfully as a modulation > transformer with this type of setup even though there is no air gap in > the transformer. There is no worry about core saturation because there > is no DC current on the transformer. > > A large enough choke for this application can be had by putting > several chokes in series to obtain the required inductance. Regular > power supply chokes work fine. Do not use a swinging choke! It has no > air gap and will saturate. > > A TV transformer will not work well as a choke because it has no air > gap and the core will saturate quickly with DC going through it. > > Cathode modulation is very similar to grid modulation in performance. > After all audio is placed between the grid and cathode just the same > as it is with conventional grid modulation. The amount of cathode to > plate modulation is minimal. > > Screen modulation is similar in performance to grid modulation also. > Efficiency is around 35% carrier efficiency. Very tricky to tune up > properly. > > Low level modulation with a linear amplifier behind the modulated > driver also has an efficiency of around 35%. Excellent AM can be > generated this way as is done with some SSB transmitters in the AM > mode. If properly set up one can not tell the difference between it > and a high level plate modulated transmitter except that the plate > modulated transmitter will probably have higher distortion. > > 73 > Gary K4FMX Oh, my gosh, you're right, Gary! It is not Heising modulation. For 60 years now I've had the mistaken impression that "Heising" implied simply that a series choke was used in the plate/screen supply to allow ANY modulation to be applied, either by modulator tube directly, or through a suitable capacitor. I am embarrased. "Googling" brought up a whole lot of other aspects of high level modulation that I didn't know (or hopefully just forgot!) Does anyone remember negative peak clipping that was the rage about 1958 or so? (Amateur only, as far as I know)...... If the scope wasn't lying, one of my home brew "high level" AM rigs was capable of modulation of over 100%. There was an awful lot of controvery at the time, and our nearest FCC chief engineer said that he didn't care if it did, it was still illegal. Sigh. Old Chief Lynn, W7LTQ Article: 97474 of rec.radio.amateur.homebrew From: "5itu" References: <446ee646$0$19697$8fcfb975@news.wanadoo.fr> Subject: Re: Transformer for PA Date: Mon, 22 May 2006 18:25:11 +0200 Message-ID: <4471e5e3$0$21258$8fcfb975@news.wanadoo.fr> HI, Thanks a lot for your answers ! 73, Daniel Article: 97475 of rec.radio.amateur.homebrew From: dplatt@radagast.org (Dave Platt) Subject: Re: Vector network analysis question Date: Mon, 22 May 2006 18:22:03 -0000 Message-ID: <12740abn01cvg07@corp.supernews.com> References: <1148251273.804190.221090@g10g2000cwb.googlegroups.com> <1148257742.429945.239100@i39g2000cwa.googlegroups.com> <1148289728.231197.223160@j55g2000cwa.googlegroups.com> >Okay, thanks. I must admit it is symptomatic of the load's center pin >not quite making contact for some reason, even though the load is fully >screwed home. But the same thing happens with 3 different loads! >I'm using the T/R test set, by the way, although I don't see how that >could explain the problem. I don't have the full S-parameter bridge but >am in the market for one. If you're using N connectors, check the center pins of the females. Make sure that they aren't splayed open. The local repeater association I'm a part of has had repeated problems with splayed N connectors. They can be caused by a couple of problems. A botched install of an N male can cause its center pin to project too far forwards, out of the shell. We've also seen some N adapters (Chinese-made I believe) whose center pin was larger than usual in diameter, or was not tapered in the usual way. In either case, if you screw an N male connector with a bad center pin into an N female, the male's pin can force the split segments of the center female pin outwards. Once this happens, a _good_ N male connector's pin may not make reliable contact with the female's damaged center pin. Intermittent nastiness can occur. It's sometimes possible to bend the female's split pin sections back together with needle-nose pliers, creating a repair which may or may not be permanent. A better solution is to replace the damaged female connectors entirely, and inspect all N male plugs and discard any whose center pins are too large in diameter, not tapered properly, or project too far out of the shell. I suppose that similar problems might occur on BNC or SMA connectors as well, for related reasons. -- 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: 97476 of rec.radio.amateur.homebrew From: Gary Schafer Subject: Re: Modulation Inductor? Date: Mon, 22 May 2006 15:33:59 -0400 Message-ID: References: <9m7172hknjg8iits6h40c4cmdf97h5dmp9@4ax.com> On Sun, 21 May 2006 18:27:52 -0700, "Lynn Coffelt" wrote: > >"Gary Schafer" wrote in message >news:9m7172hknjg8iits6h40c4cmdf97h5dmp9@4ax.com... >> >> It looks like AM is really becoming a "lost art". Of all the responses >> here, only one or two guy knows what you are talking about. >> >> The purpose of the choke inductor like you are describing is to keep >> the DC off the secondary of the modulation transformer. This allows >> the use of a modulation transformer with much less iron, which will >> give better low frequency response. If the finals DC current is run >> through the modulation transformer, as is commonly done, there needs >> to be an air gap in the transformer to keep the core from saturating >> from the DC current. The bigger the air gap the less inductance, the >> greater amount of DC current it can handle before saturation and the >> poorer low frequency response. To increase the inductance with a >> larger air gap requires more iron (larger core) to bring the >> inductance back up. >> >> By using a choke and capacitivly coupling the audio from the >> modulation transformer to the final plate there is no DC on the >> secondary of the modulation transformer to cause saturation. The >> modulation transformer then can be any audio transformer. It doesn't >> need an air gap. The transformer can have much less iron in it for the >> same amount of inductance as one with an air gap. Very good low >> frequency response can be had this way. >> >> By the way the screens of the final tubes need to be modulated along >> with the plates too. The easy way is to supply the screens through a >> dropping resistor from the top of the choke, the same point that feeds >> the plates. >> >> THIS IS NOT HEISING MODULATION. It is regular old plate modulation >> just like you would do with a conventional modulation transformer. >> >> Yes power transformers can be used quite successfully as a modulation >> transformer with this type of setup even though there is no air gap in >> the transformer. There is no worry about core saturation because there >> is no DC current on the transformer. >> >> A large enough choke for this application can be had by putting >> several chokes in series to obtain the required inductance. Regular >> power supply chokes work fine. Do not use a swinging choke! It has no >> air gap and will saturate. >> >> A TV transformer will not work well as a choke because it has no air >> gap and the core will saturate quickly with DC going through it. >> >> Cathode modulation is very similar to grid modulation in performance. >> After all audio is placed between the grid and cathode just the same >> as it is with conventional grid modulation. The amount of cathode to >> plate modulation is minimal. >> >> Screen modulation is similar in performance to grid modulation also. >> Efficiency is around 35% carrier efficiency. Very tricky to tune up >> properly. >> >> Low level modulation with a linear amplifier behind the modulated >> driver also has an efficiency of around 35%. Excellent AM can be >> generated this way as is done with some SSB transmitters in the AM >> mode. If properly set up one can not tell the difference between it >> and a high level plate modulated transmitter except that the plate >> modulated transmitter will probably have higher distortion. >> >> 73 >> Gary K4FMX > > Oh, my gosh, you're right, Gary! It is not Heising modulation. For 60 >years now I've had the mistaken impression that "Heising" implied simply >that a series choke was used in the plate/screen supply to allow ANY >modulation to be applied, either by modulator tube directly, or through a >suitable capacitor. > I am embarrased. "Googling" brought up a whole lot of other aspects of >high level modulation that I didn't know (or hopefully just forgot!) > Does anyone remember negative peak clipping that was the rage about >1958 or so? (Amateur only, as far as I know)...... If the scope wasn't >lying, one of my home brew "high level" AM rigs was capable of modulation of >over 100%. There was an awful lot of controvery at the time, and our nearest >FCC chief engineer said that he didn't care if it did, it was still illegal. >Sigh. >Old Chief Lynn, W7LTQ > Hello Chief Lynn, You are a couple of years ahead of me. I didn't get started until around 1960. I built a small modulator a few years ago and played around with negative peak clipping. Never could get it to sound good though. It will allow higher positive peak modulation without over modulating in the negative direction but the clipping on the negative side created a lot of distortion. Broadcast stations regularly run around 120% positive peaks and near 100% negative but they usually do it with clipping at low levels and clean things up after the clipping. I remember hearing about the FCC being in a quandary about some of the super modulation schemes like the Taylor system that could create upwards of 150% or greater positive modulation. 73 Gary K4FMX Article: 97477 of rec.radio.amateur.homebrew From: biascomms Subject: Re: Modulation Inductor? References: <1148322180.668131.164920@j73g2000cwa.googlegroups.com> Message-ID: Date: Mon, 22 May 2006 19:41:00 GMT K7ITM wrote: > Low level modulation is a huge waste of RF power?? Hey, _AM_ is a huge > waste of RF power, and of spectrum to boot! Except with unusual > modulating waveforms, >2/3 of the power is in a useless carrier. Now, > compared with plate modulation of the PA, low level AM modulation > followed by a linear amp may be somewhat less efficient (though a waste > of DC power, not RF power), but remember, the modulator, presumably > being a linear audio amplifier, isn't all that efficient either. In > addition, there ARE ways to generate AM with low level modulation and > efficient RF amplification--they have been used in AM broadcast > transmitters. > > For the cost of a good high-level modulator, how many kilowatt-hours > can you buy? > > Cheers, > Tom The only modulation method that I've ever found to be of any real efficiency in generating AM is "outphasing" or "ampliphase". You can use the /most/ effective PA designs - optimised FET-based Class E stages can be over 90% efficient! This approach completely obviates all the problems with modulation transformers or big chokes. Haven't tried it with valves ("tubes" - US) - perhaps that should be a future project. Bob -- Everything gets easier with practice, except getting up in the morning! Article: 97478 of rec.radio.amateur.homebrew From: biascomms Subject: Re: Modulation Inductor? References: <9m7172hknjg8iits6h40c4cmdf97h5dmp9@4ax.com> Message-ID: <6zocg.73764$wl.3258@text.news.blueyonder.co.uk> Date: Mon, 22 May 2006 19:47:14 GMT Gary Schafer wrote: > Cathode modulation is very similar to grid modulation in performance. > After all audio is placed between the grid and cathode just the same > as it is with conventional grid modulation. The amount of cathode to > plate modulation is minimal. Correct, and the distortion can be pretty nasty, too. > Screen modulation is similar in performance to grid modulation also. > Efficiency is around 35% carrier efficiency. Very tricky to tune up > properly. It was the /only/ type of AM I used at first, as I was unable to get big mod transformers. It worked well enough, though it was difficult to get close to 100% mod. Lots of envelope feedback cured the non-linearity distortions. > Low level modulation with a linear amplifier behind the modulated > driver also has an efficiency of around 35%. Excellent AM can be > generated this way as is done with some SSB transmitters in the AM > mode. If properly set up one can not tell the difference between it > and a high level plate modulated transmitter except that the plate > modulated transmitter will probably have higher distortion. Low-level mod with a linear is very inefficient (with respect to DC input), but is sometimes the only really practical way to proceed. Again, lots of envelope feedback can sort out the distortions caused by less than perfect PAs! Bob -- Everything gets easier with practice, except getting up in the morning! Article: 97479 of rec.radio.amateur.homebrew From: "JC" References: <1148059976.764499.190990@38g2000cwa.googlegroups.com> <1p3472dgf4naqcbiv1feesst244slrc9qo@4ax.com> Subject: Re: Modulation Inductor? Message-ID: Date: Mon, 22 May 2006 23:32:38 GMT >> >>www.telstar-electronics.com > > Looking at your web site I see you seem to manufacture CB amplifiers? > I also see you fail to post the 3rd and 5th order intermodulation > performance info. They must be pretty bad. > Also no low pass filter to attenuate the harmonics. -30 db second and > third harmonics are unacceptable. And those are at below power spec > on the amplifier. > > How do you measure peak envelope power? > Where do you come up with PEP at 3 times carrier power? > What makes you think that PEP is going to be any greater than the CW > power output capability of the amplifier? > > 73 > Gary K4FMX > Gary, I think you are on to something. On another group I ran across something similar, and this guy rated his amp at 100 watts AM or 180 watts PEP. I never got through to the guy. In his defense, CB'ers rate amps on 'S' meter reading, not audio quality, bandwidth, or harmonic suppression. With that crowd, a keyed mic that pins the 'S' meter rules. I am pasting one of my emails to the dude: "andy" wrote in message news:DK27f.2241$S24.156539@news.xtra.co.nz... > hmmm, i designed this amp, built the prototype and tested it, now RF parts > sell it on behalf and at no time did it mis-perform as jc says it will, > his > ideas are based on unread schematic drawings and he has never tested this > amp. > Andy, You are correct that I haven't seen it, or tested it. I don't have to. The specifications you supply are impossible to achieve. Your math is wrong. I'll go through this again: >Power levels: 100Watts AM, 180Watts PEP ** If the power is really 180 watts PEP, then the AM carrier power maximum is 25% of that or 45 watts ---NOT 100 watts. In fact to be clean, and linear I wouldn't run more than 25 watts output on AM (100 watts PEP). FACT: When you modulate AM with voice to 100% positive modulation, the peak power rises 4X from the carrier power, and the average power rises about 10-15% depending on the voice, and level. FACT: When you modulate AM with a sine wave to 100% positive modulation, the peak power rises to 4X the carrier power, and the average power rises 50% These 2 facts assume the amplifier has the upward headroom for 4X the power >from the resting carrier level. Your amp cannot do this unless you de-rate the AM power to < 50 watts (more like 25), OR reduce the maximum modulation percentage to something much lower than 100%. . Here is a reference on this: http://www.icycolors.com/nu9n/am.html#4: If we produce a 100w carrier, and the modulation level is at 100%, the peak envelope power is 400 watts. But, the peak envelope voltage max is twice the peak envelope voltage of the carrier alone. So, for example; if the carrier alone produced 20v RF peak to peak, then 100% positive modulation will produce 2 x 20v which equals 40v peak to peak voltage. Since power changes with the square of the voltage, then the power during 100% positive modulation will increase by the square, so the power increases 2 squared or 4 times! So, 100% positive modulation will produce 2 times the RF voltage and 4 times the RF power. So Andy, do you want to stand by your specifications as is, or revise them? Do your specifications assume the amplifier is being overdriven, or are you asumming the amp is kept linear by reducing the modulation percentage? You cannot have 100 watts AM and 180 watts pep without either splattering like crazy, or reducing the modulation percentage considerably. My earlier comments about splatter and distortion are important. To some in the CB crowd, they would rather emit a distorted S9+40 signal instead of a nice clean sounding S9+30 signal. To them bigger is better. I think we all know what crowd your trying to market this kit to, and as others have pointed out, this is the wrong place for that. I recall a similar amp in Motorola application notes from the late 1980's, and it was marketed by Communication Concepts for many years. This was a well engineered amplifier, and the application notes had full specifications, and scope pictures. Even this amp had gain compression on AM, even though the AM power rating was much lower than yours, and the PEP rating was similar. I'll try to find that big fat blue Motorola RF power book tonight. I think I still got it. Andy, since this forum is for posting schematics, and talking technical about them, please post your schematic. I look forward to seeing it. Regards, Jim Article: 97480 of rec.radio.amateur.homebrew From: "Big Al" Subject: wanted sockets and chimney for 4CX250 Message-ID: Date: Tue, 23 May 2006 02:12:43 GMT I'm building an amp using four Eimac 4CX250 series tubes and I'm still in need of two sockets with chimneys or what have you of similar type, either old military or civilian types. Please email off list to ve7agw(at)shaw.ca you now what to do with the "(at)" Thanks and 73...de ve7agw, Al Article: 97481 of rec.radio.amateur.homebrew Date: Tue, 23 May 2006 13:11:02 +1000 From: Will Subject: Best Way to build a calibrated S meter Message-ID: <44727d43$1_1@news.iprimus.com.au> I was wondering how commercial equipment go about calibrating the S meter and whats the best way of building a calibrated S meter that would be reliable as a professional field strength meter? Since most S meters just read AGC voltage and it would be easy to build some interface with a CPU to read voltages and calibrate this way. The question is this, is a S meter calibrated this way actually reading in a accurate way whats occurring at the antennas terminal. Since most antenna inputs are not 50 ohms J0, how would you design a system like a spectrum analyzer that measures signal voltage at the antenna terminal?. I would be interested in some ideas, i am homebrewing a shortwave receiver however i wanted a calibrated S meter in Dbuv, Dbm, S units and Millivolts. I also want to use a calibrated antenna for a Antenna factor input to have a meaningful long term view of propagation signal strength. Thanks Will Article: 97482 of rec.radio.amateur.homebrew From: "Kevin & Natalia" Subject: Control Unit for Home Built Rotator from Pitch-Prop Motor Date: Tue, 23 May 2006 21:52:19 +1200 Message-ID: <1148377755.519950@ftpsrv1> Hi All, I acquired a Pitch-Prop motor a number of years ago, with the intention of building a antenna rotator. I still have the intention of doing this, and have checked the motor for operation. This works out very nice, and was able to control it to different speeds with different voltage. I have a construction design for the mounting of the motor and gearbox to the tower, and antenna. The problem I have now, is I wish to construct a suitable control unit, with digital readout, and the possibility of controlling via a mini PIC control, or via PC. I have searched the internet without much success, so my next course of action was to see if anyone on these groups might be of help. So I put my hands up for HELP! :) Any help would be gratefully received. Thanks in Advance. Kevin, ZL1KFM. Article: 97483 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: Best Way to build a calibrated S meter Message-ID: <87u5725t409mi2vmoo1n17khokfucb98eu@4ax.com> References: <44727d43$1_1@news.iprimus.com.au> Date: Tue, 23 May 2006 12:14:13 GMT On Tue, 23 May 2006 12:16:27 +0100, "Reg Edwards" wrote: >Replace the meter scale with a white card and calibrate it yourself >with pen and ink. You will also need a signal generator and an >attenuator. > >Don't forget, an S-meter is a power or wattmeter. It indicates signal >STRENGTH. S9 = 50 pico-watts. Only by coincidence and only in a 50 ohm system elsewhere S9 is 50 uV (microVolts) equals 50pW. Many VHF radios the common standard is S9 is 5uV. Of course that would all be nice but half the radios are not calibrated at all accurately and the "S unit" while presumed to be 6db varies all over the map most being close to 3-4db Sunit near the low end and approaching 5db Sunit near S9 and none hold calibration at S9+20db. Its uncommon for radios have a log rather than linear detector and usually the agc is somewhat log but rarely accurately so. It's easy to test with a calibrated RF voltage source. So happens Elecraft makes a calibrated signal source kit. Also any of the better signal generators (800series and similar) are calibrated output levels if working right. set your meter so that a 50uv signal is at the S9 mark and remember that most meters read windspeed. Allison >---- >Reg. > Article: 97484 of rec.radio.amateur.homebrew From: Jeroen Belleman Subject: Re: Vector network analysis question Date: Tue, 23 May 2006 13:59:26 +0200 Message-ID: References: <1148251273.804190.221090@g10g2000cwb.googlegroups.com> <1148257742.429945.239100@i39g2000cwa.googlegroups.com> <1148289728.231197.223160@j55g2000cwa.googlegroups.com> <12740abn01cvg07@corp.supernews.com> <1148349960.688130.228200@i40g2000cwc.googlegroups.com> <1148376846.131725.149370@j55g2000cwa.googlegroups.com> <1148383854.891849.41040@j55g2000cwa.googlegroups.com> paul@burridge8333.fsbusiness.co.uk wrote: > Since posting earlier I've been on to the actual manufacturers and they > reckon these plugs are actually 50 ohms. So the supplier's insist > they're 75 and the makers say they're 50! I need to know for sure, as > one or the other is in error. How can one tell, by visual inspection > and or physical measurement, which type is which? There must be > something that's visibly different about the two types. Yes, look at the thickness of the central pin. A 50 Ohm connector has a central pin of some 1.6mm thick. The 75 Ohm version is a mere needle, something like 0.8mm. It's one of my long-time gripes about coaxial connectors that N and BNC series of the two impedance levels are sufficiently compatible to mate together, but not enough to do so without damage. In a lab with someone ignorant of this fact, it's a source of endless trouble. Jeroen Belleman Article: 97485 of rec.radio.amateur.homebrew Date: Tue, 23 May 2006 23:15:20 +1000 From: Will Subject: Re: Best Way to build a calibrated S meter References: <44727d43$1_1@news.iprimus.com.au> Message-ID: <44730ae6_1@news.iprimus.com.au> Reg Edwards wrote: > Replace the meter scale with a white card and calibrate it yourself > with pen and ink. You will also need a signal generator and an > attenuator. > > Don't forget, an S-meter is a power or wattmeter. It indicates signal > STRENGTH. S9 = 50 pico-watts. > ---- > Reg. > > Yeah thats for that tip. But the question is how do you actually build a piece of electronics that measures signal levels at the receiver terminals. Or is it reading agc voltage just as accurate. The problem the method you described is that it will vary from band to band. I just wonder how field strength meters are designed, especially the new solid state ones. Spectrum analyzers too have a pretty flat response. I want to build this ability into my homebrew receiver much the same way a selective level meter works. Maybe someone has done it. Will Article: 97486 of rec.radio.amateur.homebrew From: Paul Keinanen Subject: Re: Best Way to build a calibrated S meter Message-ID: <9m0672t4afp02rttvafmrgfa7k8k7aa35g@4ax.com> References: <44727d43$1_1@news.iprimus.com.au> Date: Tue, 23 May 2006 16:26:50 +0300 On Tue, 23 May 2006 12:16:27 +0100, "Reg Edwards" wrote: >Replace the meter scale with a white card and calibrate it yourself >with pen and ink. You will also need a signal generator and an >attenuator. If you derive the S-meter reading from the a.g.c. control voltage, be prepared to perform the calibration at various temperatures, since the gain of simple IF-strips vary with temperature (and thus need a different amount of a.g.c.), unless the gain is controlled by passive components only. With various front end filter for various frequency bands and attenuation depending of the frequency, you would have to perform the calibration on several frequencies. Instead of a pen and ink, it would be more practical to use a micro controller with sufficient non-volatile storage for the conversion tables and use analog inputs for a.g.c. voltage and temperature and some kind of input for the frequency being received. With these inputs and the conversion table, a voltage proportional of the log of the antenna terminal power could be generated. Paul OH3LWR Article: 97487 of rec.radio.amateur.homebrew Date: Tue, 23 May 2006 15:53:57 +0200 From: ADMIN Subject: Earn up to 1000 $ per month only for reading your Mails!!!!!!!! Message-ID: <44731244$0$59880$afc38c87@news6.united-newsserver.de>

 

Article: 97488 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: Best Way to build a calibrated S meter Message-ID: <0k7672tnoml74egmhoufl62mnaor633quj@4ax.com> References: <44727d43$1_1@news.iprimus.com.au> <87u5725t409mi2vmoo1n17khokfucb98eu@4ax.com> <8qqdnZNYh90Vlu7ZnZ2dnUVZ8qWdnZ2d@bt.com> Date: Tue, 23 May 2006 14:49:53 GMT On Tue, 23 May 2006 14:14:26 +0100, "Reg Edwards" wrote: > > wrote >> Only by coincidence and only in a 50 ohm system elsewhere >> S9 is 50 uV (microVolts) equals 50pW. > >========================================== >Allison, I'm afraid you are not quite correct about coincidences. > >The beauty of calibrating an S-meter in watts is that the result is >independent of receiver impedance. > >Of course, there must be a conjugate match between antenna and >receiver. And there usually is. This is taken care of in the >calibration process. At VHF it's not uncommon that the match is poor for better noise response. You can calibrate anyway but, variables then vary. >The received signal STRENGTH is indicated in watts, which is all one >wants to know. When reading the meter, who cares about what impedance >the measuring instrument happens to be? > >To sum up : There is a transmitter of given power output. There is a >radio path which is an attenuator, And there is a received signal >signal strength meter which indicates watts. As long as everything is 50ohm. If it isn't then your only measuring voltage across an unknown hence power is effective;y unknown. >The overall loss between transmitter and power meter may be deduced in >terms of decibels. Professional radio engineers do it all the time. Yep, but there is a fudge factor as the pathloss is a variable. Usually it's specified as "not less than" for contours. >It can be misleading to think in terms of S9 = 50 uV when one doesn't >know what the receiver input impedance is. >---- >Reg, G4FGQ > Two caveats, rarely are RX input impedences 50 ohms and there is no guarentee that the antenna is 50 ohms. These things can be assured during calibration but it ends there usually. The other is of course the linearity/nonlinearity of the AGC system and band to band variation. My favorte radio has a old windspeed meter, never bothered to alter the scale so I calibrate ~50uV (VHF radio) for 60mph. (0-90mph on a 270 degree scale). Besides the novelty the scale is perfect for the various current and voltage points that are testable. Allison Article: 97489 of rec.radio.amateur.homebrew Date: Wed, 24 May 2006 01:40:16 +1000 From: Will Subject: Re: Best Way to build a calibrated S meter References: <44727d43$1_1@news.iprimus.com.au> <44730ae6_1@news.iprimus.com.au> <9PydnUbJBYp2vO7ZRVny1w@bt.com> Message-ID: <44732ce2_1@news.iprimus.com.au> Reg Edwards wrote: > "Will" wrote >> I just wonder how field strength meters are designed, especially the > new >> solid state ones. Spectrum analyzers too have a pretty flat > response. I >> want to build this ability into my homebrew receiver much the same > way >> a selective level meter works. Maybe someone has done it. >> > =========================================== > > The accuracy of S-meters varies from one band to another because the > receiver input impedance varies from one band to another. Even from > one end of a band to the other, especially if the input stage is > tuned. > > Also, the stage-gain of an RF stage can vary very much from one band > to another. > > To ensure a consistent gain it is necessary to convert to the > intermediate frequency (IF) at the very first stage of a receiver. > Preferably using a high-level, balanced diode-bridge, modulator. > > The IF stages can be assumed to have a constant, wide-band gain, > except, of course, for the automatic gain control (AGC) action. > > Then ensure that the receiver input impedance is constant (usually 50 > ohms) over the whole HF range of the receiver. Remember the S-meter > is a power or watt-meter. > > It so happens that with dual-gate FET's, and 3 or 4 IF amplifier > stages, a meter which responds to AGC volts will fairly accurately > indicate S-units and dB above S9 in a linear fashion. > > However, below about S4 the linearity of S-meter readings begins to > fail. And you will have to make and calibrate your own meter scale. > There's no way of avoiding it! That is unless you can mentally > visualise what the scale ought to look like as you use it. > > Accurate commercial field strength meters use antennas dedicated to > the job, conjugate-matched to the receiver, are insensitive to weak > signals, are narrow band and are very expensive. > > To obtain an S-meter scale to be proud of, you will have to use pen > and ink with a signal generator and 100-dB stepped attenuator. > Attempts to calibrate the scale with clever, highly complicated > electronics will get you nowhere in a long time. And will cost you > more than the remainder of the receiver. > > Sorry to be so despondent. > ---- > Reg, G4FGQ > > Thanks Reg for the summary. I think the Flex radio and the Winradio have the ability to be calibrated accurately via a look up table. I always admired shortwave receivers like the R&S EK 2000 which had a accurate meter calibrated in the DbUv scale. I think i will just have to abandon my super accurate S meter project. Will Article: 97490 of rec.radio.amateur.homebrew From: "Caveat Lector" References: <44727d43$1_1@news.iprimus.com.au> Subject: Re: Best Way to build a calibrated S meter Message-ID: <64Gcg.177511$bm6.76448@fed1read04> Date: Tue, 23 May 2006 08:41:43 -0700 Will take a look at URL: http://www.ac6v.com/sunit.htm Maybe the National Semiconductor NE604 IF amplifier IC would be worth looking into. Claims say it provides an accurate signal strength logarithmic output that closely tracks the input signal level over a wide dynamic range that could possibly be used for driving an S meter circuit. -- CL -- I doubt, therefore I might be ! "Will" wrote in message news:44727d43$1_1@news.iprimus.com.au... >I was wondering how commercial equipment go about calibrating the S meter >and whats the best way of building a calibrated S meter that would be >reliable as a professional field strength meter? > > Since most S meters just read AGC voltage and it would be easy to build > some interface with a CPU to read voltages and calibrate this way. The > question is this, is a S meter calibrated this way actually reading in a > accurate way whats occurring at the antennas terminal. Since most antenna > inputs are not 50 ohms J0, how would you design a system like a spectrum > analyzer that measures signal voltage at the antenna terminal?. I would be > interested in some ideas, i am homebrewing a shortwave receiver however i > wanted a calibrated S meter in Dbuv, Dbm, S units and Millivolts. I also > want to use a calibrated antenna for a Antenna factor input to have a > meaningful long term view of propagation signal strength. > > Thanks > Will Article: 97491 of rec.radio.amateur.homebrew From: Robert Kubichek Subject: Re: Control Unit for Home Built Rotator from Pitch-Prop Motor Date: Tue, 23 May 2006 11:12:02 -0500 Message-ID: <4dgqilF1987e2U1@individual.net> References: <1148377755.519950@ftpsrv1> Kevin & Natalia wrote: > Hi All, > > I acquired a Pitch-Prop motor a number of years ago, with the intention of > building a antenna rotator. > I still have the intention of doing this, and have checked the motor for > operation. This works out very nice, and was able to control it to different > speeds with different voltage. > I have a construction design for the mounting of the motor and gearbox to > the tower, and antenna. > > The problem I have now, is I wish to construct a suitable control unit, with > digital readout, and the possibility of controlling via a mini PIC control, > or via PC. > > I have searched the internet without much success, so my next course of > action was to see if anyone on these groups might be of help. > So I put my hands up for HELP! :) > > Any help would be gratefully received. > > Thanks in Advance. > > Kevin, ZL1KFM. > > It is entirely doable, check here "http://forums.parallax.com/forums/default.aspx" for ideas on how to implement your project using a Basic Stamp... I would do it with digital position sensing, with an lcd display showing direction of antenna.. Bob N9LVU Article: 97492 of rec.radio.amateur.homebrew From: fmmck@aol.com (Fred McKenzie) Subject: Re: Vector network analysis question Date: Tue, 23 May 2006 12:30:33 -0400 Message-ID: References: <1148251273.804190.221090@g10g2000cwb.googlegroups.com> <1148257742.429945.239100@i39g2000cwa.googlegroups.com> <1148289728.231197.223160@j55g2000cwa.googlegroups.com> <12740abn01cvg07@corp.supernews.com> <1148349960.688130.228200@i40g2000cwc.googlegroups.com> <1148376846.131725.149370@j55g2000cwa.googlegroups.com> <1148383854.891849.41040@j55g2000cwa.googlegroups.com> <1148394928.476606.61360@g10g2000cwb.googlegroups.com> In article <1148394928.476606.61360@g10g2000cwb.googlegroups.com>, paul@burridge8333.fsbusiness.co.uk wrote: > On reconnecting everything, however, the > problem still persists, although the 50 ohm load is now showing as very > close to a dead short; virtually the same spot on the Smith chart > overlay as when the socket is shorted, in fact. Once again, the other > loads do likewise and they all check out fine as 50 ohms with a DVM. > Very strange! I wonder if there's some setting I may have got wrong > somewhere. :-/ Paul- What would be the result of calibrating the system with an inductive "short"? If it can be done, results of testing with a good 50 Ohm load might be skewed. Fred Article: 97493 of rec.radio.amateur.homebrew From: fmmck@aol.com (Fred McKenzie) Subject: Re: Best Way to build a calibrated S meter Date: Tue, 23 May 2006 12:48:18 -0400 Message-ID: References: <44727d43$1_1@news.iprimus.com.au> <87u5725t409mi2vmoo1n17khokfucb98eu@4ax.com> <8qqdnZNYh90Vlu7ZnZ2dnUVZ8qWdnZ2d@bt.com> <0k7672tnoml74egmhoufl62mnaor633quj@4ax.com> In article <0k7672tnoml74egmhoufl62mnaor633quj@4ax.com>, Allisonnospam@nouce.bellatlantic.net wrote: > Two caveats, rarely are RX input impedences 50 ohms and there is no > guarentee that the antenna is 50 ohms. Allison- Such is life. However you can assume that both are 50 Ohms and use a resistive pad between the signal generator and the receiver when calibrating. When making a reading, use a pad between the unknown signal source and the receiver. Without a sophisticated system capable of determining impedances while making measurements, this may be the best you can do. Fred Article: 97494 of rec.radio.amateur.homebrew From: "Steve N." Subject: Re: Best Way to build a calibrated S meter Date: Tue, 23 May 2006 17:33:23 -0500 Message-ID: References: <44727d43$1_1@news.iprimus.com.au> <64Gcg.177511$bm6.76448@fed1read04> "Caveat Lector" wrote in message news:64Gcg.177511$bm6.76448@fed1read04... > Will take a look at URL: > http://www.ac6v.com/sunit.htm > > > Maybe the National Semiconductor NE604 IF amplifier IC would be worth > looking into. Claims say it provides an accurate signal strength logarithmic > output that closely tracks the input signal level over a wide dynamic range > that could possibly be used for driving an S meter circuit. > > -- > CL -- I doubt, therefore I might be ! This is ok, but the one thing is that any Signal strength IC like the 604 has a constant slope and the S-Meter will be rather compressed in the 0-9 s-units range compared to the over S9 range (obviously fixable with meter scale). I don't recall the 604's dynamic range. You could make a two slope correction above S9, but I'd have to do some scratch paper work to figure out the circuit [ probably as simple as a resister and diode in the right place]. Or use two of them and change the gain into one to get the different slope. I don't recall the 604's dynamic range. I have some SLx16...oops can't remember the numbers (? 1316?... 1613? ) , that are cascaded for large dynamic range log amps. Just some ideas. 73, Steve, K9DCI Article: 97495 of rec.radio.amateur.homebrew From: "Steve N." Subject: Re: 13.8V high current power supply - update Date: Tue, 23 May 2006 17:45:22 -0500 Message-ID: References: <1147103416.176308.205570@y43g2000cwc.googlegroups.com> <1147280376.352051.67700@j73g2000cwa.googlegroups.com> <4p25625k1r15c8beus1v1oo99m24b39rgu@4ax.com> <4rt562pa8vn5frfk7t8medr0nr3dhhvuqn@4ax.com> <126701f6kpcp691@corp.supernews.com> Mike, I'm confused. The "crowbar" I am familiar with is an over voltage protection device. If the supply output voltage goes up too high, it triggers, turns on providing a very lo resistance load and effectively shorting the output. Thus it initiates the over current protection device, whatever that is. If I read this correctly, it appears you are PLACING a short on the supply and testing the over current protector... It sounds like "Crowbar" is also used for an over- current protector... I always thought the term came from using a real 1 inch diameter steel crowbar (the tipe used in Christmas Story to open the crate containing the leg lamp) to short the output of a power supply as a really good way to get to zero volts in a hurry - but only in principle, of course. 73, Steve, K9DCI "Mike Andrews" wrote in message news:e4015o$c5s$3@puck.litech.org... > Hmmmm ... > > Bobbie Barmore was discussing IOT power supplies and their crowbars on > the GowBugs list a few months back. Seems that the test to see if the > crowbar's good is pretty simple: > > 1) Turn everything off > 2) Safety tag and padlock all the breakers and the START switch > 3) Ground everything that even might think about biting > 4) Put a piece of (?) 32-gauge wire between HV and ground. > 5) Pull the shorting sticks, button everything up, unlock and > untag the breakers, untag the START switch > 6) Make sure everyone's clear and safe > 7) Push the START switch > > The power supply's good for something like 700 mA at 35 KVDC, and it is > a _really_ bad idea to get across it if you might pass less than abount > 700 mA. But the wire's good for more than 700 mA, and so will look like a > short to the PS. > > If the wire melts, vaporizes, or explodes, then the crowbar circuit is bad. > It should be unaffected by the test. Put 35 KV across a piece of 32ga wire > without blowing it up. > > Hydrogen thyratrons to dump the power, and fast-acting circuit breakers to > Shut Things Down NOW, appear to be the way to protect the wire from the PS. > Fascinating technology. > > Homebrew _that_. > > -- > Mike Andrews, W5EGO > mikea@mikea.ath.cx > Tired old sysadmin Article: 97496 of rec.radio.amateur.homebrew From: "Mike Andrews" Subject: Re: 13.8V high current power supply - update Date: Tue, 23 May 2006 23:38:02 +0000 (UTC) Message-ID: References: <1147103416.176308.205570@y43g2000cwc.googlegroups.com> <1147280376.352051.67700@j73g2000cwa.googlegroups.com> <4p25625k1r15c8beus1v1oo99m24b39rgu@4ax.com> <4rt562pa8vn5frfk7t8medr0nr3dhhvuqn@4ax.com> <126701f6kpcp691@corp.supernews.com> Steve N. wrote: > Mike, > I'm confused. The "crowbar" I am familiar with is an over voltage > protection device. If the supply output voltage goes up too high, it > triggers, turns on providing a very lo resistance load and effectively > shorting the output. Thus it initiates the over current protection device, > whatever that is. > If I read this correctly, it appears you are PLACING a short on the supply > and testing the over current protector... > It sounds like "Crowbar" is also used for an over- current protector... > I always thought the term came from using a real 1 inch diameter steel > crowbar (the tipe used in Christmas Story to open the crate containing the > leg lamp) to short the output of a power supply as a really good way to get > to zero volts in a hurry - but only in principle, of course. > 73, Steve, K9DCI You're on the money as to what gets done to save the IOT. It's a lot more expensive than the entire power supply, and so the PS gets to suck it up between the time the hydrogen thyratron (or ignitron or whatever) turns on and the time the overcurrent limiter or magnetic- controlled breaker on the PS input decides to Turn Things Off Right Damnit _Now_. You're also on the money about crowbars being used as overcurrent protection as well as overvoltage protection. My experience with crowbars involves both the voltage-foldback flavor and the current-foldback flavor. Sometimes you'll be running something at constant current and want to limit the voltage across it; for that, you fold the curent back to keep from exceeding the max voltage. Sometimes you'll be running something at constant voltage and want to limit the current through it; for that, you fold the voltage back to keep from exceeding the max current. In the extreme case, you cut the voltage across, or current through, a device off by putting a short across the PS output. We had some lab PSes at the NASA Manned Spacecraft Center with adjustable voltage _and_ current limits, though none with high-capacity crowbars involving ignitrons, hydrogen thyratrons, and such (to me) exotic devices. But both voltage and current limits came in very handy. -- Mike Andrews, W5EGO mikea@mikea.ath.cx Tired old sysadmin Article: 97497 of rec.radio.amateur.homebrew From: "Kevin & Natalia" Subject: Re: Control Unit for Home Built Rotator from Pitch-Prop Motor Date: Wed, 24 May 2006 11:52:31 +1200 Message-ID: <1148428168.920547@ftpsrv1> References: <1148377755.519950@ftpsrv1> Hi Tim, My electronics skills are fairly good, I have built many projects over the time. What I was wanting to do, is have a control box in the shack with a readout and left/right controls. And have the provision to also be able to have a PC control it. I like the Pitch-prop motor, as it is strong, and can be controlled easy. The way I control it at the moment, is via a 2 voltage system. The pitch-prop runs at 36volts for full speed, and when I wish to slow it down for small movements, I use a second set of controls at 15volts. Not the best way of doing it, but it works. I then look out the window and see where it is pointing. I know where N, E, S, W are on my section. As to price on the parts, I would like to keep it down to around a couple of hundred dollars. :) Regards and thanks for your input. Kevin, ZL1KFM www.qsl.net/zl1hk "Tim Wescott" wrote in message news:hOmdnZarFMOuh-7ZnZ2dnUVZ_vqdnZ2d@web-ster.com... >> >> > Excepting the readout, this should be a fairly routine motor control > problem. Depending on what you want to do your control box could be as > simple as a current-limited power supply and a couple of switches or as > complex as a fully fed-back motion control system. > > How's your electronics skills, and how fancy do you want it to be? > > -- > > 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: 97498 of rec.radio.amateur.homebrew Date: Wed, 24 May 2006 15:55:36 +1000 From: Will Subject: Re: Best Way to build a calibrated S meter References: <44727d43$1_1@news.iprimus.com.au> <44730ae6_1@news.iprimus.com.au> <1148429660.396672.45970@u72g2000cwu.googlegroups.com> Message-ID: <4473f55e_1@news.iprimus.com.au> K7ITM wrote: > The way that spectrum analyzers are built is typically to use > calibrated attenuators and linear gain stages that have very low > distortion (and similarly low "compression"). Then it becomes a matter > of determining the voltage after amplification. They do NOT use AGC > voltage, or at least not anything like the AGC used in a typical ham > receiver. The way we do it here is to digitize the RF signal and do > some appropriate digital signal processing on it (e.g., FFT) to display > the spectrum and to calculate amplitudes and band powers and the like. > Modern digitizers are very linear indeed and can be used to measure > signal amplitudes over a range in excess of 120dB with relative > accuracy far better than an S meter over most of that range, and still > considerably better even at the bottom end of the range. It doesn't > even take a huge number of bits in the digitization to do it; consider > that a typical delta-sigma ADC is a one-bit converter followed by lots > of processing gain. > > The way it can be done "on the cheap" is to use a calibrated attenuator > and a single known signal level. Then you compare your known signal > level with the unknown, adjusting the attenuator to bring your > (typically large) signal down to the same amplitude as the unknown. > > For S-meter levels of accuracy, linear non-AGC'd stages feeding one of > the RF power detectors from Analog Devices, Linear Technology or others > will work fine. Most of them have an output voltage proportional to > the log of the input voltage, and so can be calibrated to read dB > linearly on a linear meter scale. If your receiver has a good front > end, it shouldn't need AGC up through the filter following the mixer, > and you could pick off there after the filter to drive the meter > circuit. That seems overkill, but it would get you a _good_ S-meter. > Then you'd have to calibrate out the front-end gain at least per band, > assuming you have at least some front end filtering that doesn't have > the same gain (loss) on each band. > > Field strength meters that accurately measure an RF electromagnetic > field are basically spectrum analyzers fed by calibrated antennas. > > That may be beyond what you wanted to know or do, but it should give > you a pretty accurate picture of how modern commercial gear actually > does make RF voltage measurements. You could add calibration (for > absolute amplitude accuracy as well as spectral flatness) to all that > as a whole 'nuther topic, though. For example, the amplitude > characteristics of any filters the signal passes through in the > spectrum analyzer must be properly accounted for, as must temperature > drifts in instruments with high accuracy. > > Cheers, > Tom > Thanks Tom and Jim. The information you provided has given me something to think about. Even though the task is complex it can be done. I will experiment with some ideas and see if i can find a sollution. Regardless how hard it is i think its worthwile pursuing a accurate S meter. Will Article: 97500 of rec.radio.amateur.homebrew From: Eamon Skelton Subject: Re: Best Way to build a calibrated S meter Message-ID: References: <44727d43$1_1@news.iprimus.com.au> <44730ae6_1@news.iprimus.com.au> <1148429660.396672.45970@u72g2000cwu.googlegroups.com> <4473f55e_1@news.iprimus.com.au> Date: Wed, 24 May 2006 09:53:03 +0100 On Wed, 24 May 2006 15:55:36 +1000, Will wrote: > Regardless how hard it is i think its worthwile pursuing a accurate S > meter. > > Will It will make you very unpopular. People who are used to getting S9+30dB reports get quite upset when you give the a 57 :-) 73, Ed. EI9GQ. -- Linux 2.6.16 Remove 'X' to reply by e-mail. Yes, my username really is: nospam Article: 97501 of rec.radio.amateur.homebrew From: rick H Subject: Re: Vector network analysis question References: <1148251273.804190.221090@g10g2000cwb.googlegroups.com> <1148257742.429945.239100@i39g2000cwa.googlegroups.com> <1148289728.231197.223160@j55g2000cwa.googlegroups.com> <12740abn01cvg07@corp.supernews.com> <1148349960.688130.228200@i40g2000cwc.googlegroups.com> <1148376846.131725.149370@j55g2000cwa.googlegroups.com> <1148383854.891849.41040@j55g2000cwa.googlegroups.com> <1148394928.476606.61360@g10g2000cwb.googlegroups.com> <1148421999.392455.211650@j33g2000cwa.googlegroups.com> Message-ID: Date: Wed, 24 May 2006 12:01:26 GMT In sci.electronics.design paul@burridge8333.fsbusiness.co.uk wrote: > Good thinking, Fred. That's theoretically possible, I guess. But I'm > carrying out these checks purposely at only around 5Mhz to minimise > such high frequency effects. You may well be on the right lines, though! > Have you tried buzzing your home-made leads through with a DVM to confirm that they're ok (at dc) - both centre and shield of the coaxial connectors? Try discarding the test-set for a moment and just connecting Ref to the A and B inputs on the VNA (configured to measure loss/gain). If you know that your coaxial leads are ok, then you'll be checking that all the I/O ports on the VNA are working correctly. Have you confirmed that the test-set is correctly connected to the VNA? Try terminating unused I/O ports with a 50 Ohm load or with a pad (a 10dB pad makes a reasonable 50 Ohm load) and then repeating the cal and measurement. Try calibrating the VNA/test-set without the leads, just using a Male-Male adaptor instead. Then see what happens when you measure gamma with 50 Ohms dangling off the adaptor. Cheers, Rick Article: 97502 of rec.radio.amateur.homebrew From: - exray - Subject: Re: Best Way to build a calibrated S meter Date: Wed, 24 May 2006 07:58:23 -0400 Message-ID: <1278ij3jd2ms788@corp.supernews.com> References: <44727d43$1_1@news.iprimus.com.au> <44730ae6_1@news.iprimus.com.au> <1148429660.396672.45970@u72g2000cwu.googlegroups.com> <4473f55e_1@news.iprimus.com.au> Highland Ham wrote: >> It will make you very unpopular. People who are used to getting >> S9+30dB reports get quite upset when you give the a 57 :-) > > ====================================== > > Why would a serious radio amateur trying hard to use his equipment in > the best way possible be required to be popular ? > > Frank GM0CSZ / KN6WH Zoom! Article: 97503 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: Best Way to build a calibrated S meter Message-ID: References: <44727d43$1_1@news.iprimus.com.au> <87u5725t409mi2vmoo1n17khokfucb98eu@4ax.com> <8qqdnZNYh90Vlu7ZnZ2dnUVZ8qWdnZ2d@bt.com> <0k7672tnoml74egmhoufl62mnaor633quj@4ax.com> Date: Wed, 24 May 2006 13:01:00 GMT On Tue, 23 May 2006 12:48:18 -0400, fmmck@aol.com (Fred McKenzie) wrote: >In article <0k7672tnoml74egmhoufl62mnaor633quj@4ax.com>, >Allisonnospam@nouce.bellatlantic.net wrote: > >> Two caveats, rarely are RX input impedences 50 ohms and there is no >> guarentee that the antenna is 50 ohms. > >Allison- > >Such is life. However you can assume that both are 50 Ohms and use a >resistive pad between the signal generator and the receiver when >calibrating. When making a reading, use a pad between the unknown signal >source and the receiver. > >Without a sophisticated system capable of determining impedances while >making measurements, this may be the best you can do. > >Fred Yes, you can do all that and more easily. Often it means little. I rarely use my comms as measurement recievers as I have dedicated equipment for that. For those the available devices from Analog devices are excellent. For general on the air work S9 meaning whatever is mostly convenience in aiming the antennas and even then peak is the criteria. However I've used at least one radio where the S-meter was so sluggish on slow AGC and so twitchy on fast AGC that using for aiming antennas was annoying. I'd also said for most radios I've encountered the meter even if S9 was a calibrated point the the interval between points was at best wildly inaccurate. For that case the calibated point is at best moot and for any measurements the ide will be to keep a fixed point as reference and use attenuators to assign value above or below that point. Allison Article: 97504 of rec.radio.amateur.homebrew Date: Wed, 24 May 2006 14:21:12 +0100 From: Will Subject: Re: Best Way to build a calibrated S meter References: <44727d43$1_1@news.iprimus.com.au> <87u5725t409mi2vmoo1n17khokfucb98eu@4ax.com> <8qqdnZNYh90Vlu7ZnZ2dnUVZ8qWdnZ2d@bt.com> <0k7672tnoml74egmhoufl62mnaor633quj@4ax.com> Message-ID: <44745dd2_1@news.iprimus.com.au> Allisonnospam@nouce.bellatlantic.net wrote: > On Tue, 23 May 2006 12:48:18 -0400, fmmck@aol.com (Fred McKenzie) > wrote: > >> In article <0k7672tnoml74egmhoufl62mnaor633quj@4ax.com>, >> Allisonnospam@nouce.bellatlantic.net wrote: >> >>> Two caveats, rarely are RX input impedences 50 ohms and there is no >>> guarentee that the antenna is 50 ohms. >> Allison- >> >> Such is life. However you can assume that both are 50 Ohms and use a >> resistive pad between the signal generator and the receiver when >> calibrating. When making a reading, use a pad between the unknown signal >> source and the receiver. >> >> Without a sophisticated system capable of determining impedances while >> making measurements, this may be the best you can do. >> >> Fred > > Yes, you can do all that and more easily. Often it means little. I > rarely use my comms as measurement recievers as I have dedicated > equipment for that. For those the available devices from Analog > devices are excellent. > > For general on the air work S9 meaning whatever is mostly > convenience in aiming the antennas and even then peak is > the criteria. However I've used at least one radio where the > S-meter was so sluggish on slow AGC and so twitchy on fast > AGC that using for aiming antennas was annoying. > > I'd also said for most radios I've encountered the meter even if S9 > was a calibrated point the the interval between points was at best > wildly inaccurate. For that case the calibated point is at best moot > and for any measurements the ide will be to keep a fixed point as > reference and use attenuators to assign value above or below that > point. > > > Allison > I found the N6NB method using a VU meter with the AGC off very useful. However using a receiver with the AGC off is unbearable. I would have thought that a radio like the Ten Tec Orion could have easily implemented a calibrated S meter. However without hams demanding it and hams willing to live with the Guess Meter manufacturers wont bother. There is a fax station in Germany running 20 kw or so, into a vertical antenna on 13,882 or somewhere around their. Its quite useful comparing it to the many ham stations running beams and even low power with beams. Its also a useful propagation beacon. Its been on for years and i wanted to measure the signal strength and compare it to what VOACAP predicts. In private emails some people have indicated that Winradio has a calibration software option for their receivers. So that may be another option. Some users have also indicated that the RFSPACE DSP receiver likewise is quite accurate with amplitude measurements. There are options... Will Article: 97505 of rec.radio.amateur.homebrew From: Roy Lewallen Subject: Re: Vector network analysis question Date: Wed, 24 May 2006 08:32:26 -0700 Message-ID: <1278v4fqbibh08d@corp.supernews.com> References: <1148251273.804190.221090@g10g2000cwb.googlegroups.com> <1148257742.429945.239100@i39g2000cwa.googlegroups.com> <1148289728.231197.223160@j55g2000cwa.googlegroups.com> <12740abn01cvg07@corp.supernews.com> <1148349960.688130.228200@i40g2000cwc.googlegroups.com> <1148376846.131725.149370@j55g2000cwa.googlegroups.com> <1148383854.891849.41040@j55g2000cwa.googlegroups.com> Jeroen Belleman wrote: > . . . > It's one of my long-time gripes about coaxial connectors that N and > BNC series of the two impedance levels are sufficiently compatible > to mate together, but not enough to do so without damage. In a lab > with someone ignorant of this fact, it's a source of endless trouble. All the 75 ohm BNC connectors I have, have the same diameter center pin in the connection region as 50 ohm connectors. The difference is in the thickness of the dielectric around the pin in the connection region, being much thinner in the 75 ohm connectors. The pin of the 75 ohm connector is smaller only where it's in solid dielectric at the bottom of the connector. Roy Lewallen, W7EL Article: 97506 of rec.radio.amateur.homebrew From: info@tips4life.net Subject: Hundreds of Tips to Improve your Quality of life Date: 24 May 2006 14:54:25 GMT Message-ID: <447473a1$0$24314$88260bb3@free.teranews.com> --_NextPart_000097CD-0000134F-00A34413-F27D Content-Type: text/plain Content-Transfer-Encoding: 7bit Tips 4 Life - Tips To Make Your Life Better and more productive Visit Today. http://www.tips4life.net/ --_NextPart_000097CD-0000134F-00A34413-F27D-- *** Posted via a free Usenet account from http://www.teranews.com *** Article: 97507 of rec.radio.amateur.homebrew From: larry d clark Subject: what's up with eham? Message-ID: Date: Wed, 24 May 2006 18:57:24 GMT what's up with eham? haven't been able to hit the site for several days from here in the dallas area? larry kd5foy Article: 97508 of rec.radio.amateur.homebrew From: dplatt@radagast.org (Dave Platt) Subject: Re: what's up with eham? Date: Wed, 24 May 2006 19:13:46 -0000 Message-ID: <1279c3alj3said0@corp.supernews.com> References: In article , larry d clark wrote: >what's up with eham? haven't been able to hit the >site for several days from here in the dallas area? I don't know the underlying cause, but I do see the same outage here. The server for "eham.net" doesn't respond to pings, although the two machines with immediately-adjacent IP addresses do. Looks as if the server's off the air. -- 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: 97509 of rec.radio.amateur.homebrew Subject: Re: Vector network analysis question From: Mike Monett References: <1148251273.804190.221090@g10g2000cwb.googlegroups.com> <1148257742.429945.239100@i39g2000cwa.googlegroups.com> <1148289728.231197.223160@j55g2000cwa.googlegroups.com> <12740abn01cvg07@corp.supernews.com> <1148349960.688130.228200@i40g2000cwc.googlegroups.com> <1148376846.131725.149370@j55g2000cwa.googlegroups.com> <1148383854.891849.41040@j55g2000cwa.googlegroups.com> <1278v4fqbibh08d@corp.supernews.com> Message-ID: Date: Wed, 24 May 2006 15:40:51 -0400 Roy Lewallen wrote: > Jeroen Belleman wrote: >> It's one of my long-time gripes about coaxial connectors that N >> and BNC series of the two impedance levels are sufficiently >> compatible to mate together, but not enough to do so without >> damage. In a lab with someone ignorant of this fact, it's a >> source of endless trouble. >> All the 75 ohm BNC connectors I have, have the same diameter >> center pin in the connection region as 50 ohm connectors. The >> difference is in the thickness of the dielectric around the pin >> in the connection region, being much thinner in the 75 ohm >> connectors. The pin of the 75 ohm connector is smaller only where >> it's in solid dielectric at the bottom of the connector. > Roy Lewallen, W7EL Hi Roy, There's lots of room for confusion. The Kings tool FAQ implies the center contact diameter got smaller when the pin was redesigned and the old crimp die set would not work: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Why won't my Kings 2025-X-9 die set work with the 2065-X-9 connectors? With the redesign of the True 75 Ohm BNC connectors, the center contact diameter got smaller to maintain a constant 75 Ohm impedance through the connector. Consequently, the center contact crimp dimension got smaller also. The problem with the inability of the die set to crimp this new connector is probably because it is the older, larger die dimension. The Kings website has a Cross-Reference Search that lists the applicable die set for most Kings connector part numbers. http://www.kingselectronics.com/ResourceGuide/FAQs/tabid/74/Default.aspx ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ However, another manufacturer claims their new 75 ohm hardware is interchangeable with 50 ohm connectors: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TRUE 75 Ohm BNC & Connectors Where Controlled Impedance is a Necessity Emerson Network Power Connectivity Solutions is introducing its premium line of TRUE 75 Ohm BNC connectors and adapters. These flexible cable 3 Piece BNC Connectors are essential for analog and digital high frequency signals. They have been designed around MIL-STD-202 for up to a 3GHz frequency range, and are constructed of high performance materials including a machined nickel plated over brass housing, a teflon dielectric and gold plated brass contacts. These connectors are designed to eliminate distortion and impedance mismatching caused by using 50 ohm connectors on 75 ohm cables, and they safely inter-mate with standard 50 Ohm BNC connectors. http://emersonnetworkpower.com/webapp/wcs/stores/servlet/ESC/pdfs/True-75- Ohm.pdf ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ If your junkbox is anything like mine, it may have stuff purchased 20 years ago mixed with more recent purchases. So it might be worthwhile to check carefully before mating different hardware. Regards, Mike Monett Article: 97510 of rec.radio.amateur.homebrew From: gsm@mendelson.com (Geoffrey S. Mendelson) Subject: Re: what's up with eham? Date: Wed, 24 May 2006 19:51:03 +0000 (UTC) Message-ID: References: <1279c3alj3said0@corp.supernews.com> Dave Platt wrote: > > Looks as if the server's off the air. Couldn't happen to nicer people in my opinion. When I complained that they had Google ads on their site which directly supported BPL, the owner of the site told me that BPL was an INTERNET technology and since his site was RADIO related, it wasn't his concern. He also said that without Google ads, he could not keep the site alive, so he choose Google and BPL. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM IL Voice: (07)-7424-1667 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838 Visit my 'blog at http://geoffstechno.livejournal.com/ Article: 97511 of rec.radio.amateur.homebrew Subject: Re: Vector network analysis question From: Mike Monett References: <1148251273.804190.221090@g10g2000cwb.googlegroups.com> <1148257742.429945.239100@i39g2000cwa.googlegroups.com> <1148289728.231197.223160@j55g2000cwa.googlegroups.com> <12740abn01cvg07@corp.supernews.com> <1148349960.688130.228200@i40g2000cwc.googlegroups.com> <1148376846.131725.149370@j55g2000cwa.googlegroups.com> <1148383854.891849.41040@j55g2000cwa.googlegroups.com> <1278v4fqbibh08d@corp.supernews.com> Message-ID: Date: Wed, 24 May 2006 16:02:34 -0400 Mike Monett wrote: > So it might be > worthwhile to check carefully before mating different hardware. So the thought finally strikes me. How do you check the female socket dimension? Do you stick a male pin in and see how much friction there is? That could bend the contacts and damage the pin. How about checking the male pin diameter when it is already installed on a connector? There's not enough room for calipers to reach the pin. I often find the BNC connectors on my scope go intermittent due to a loose center pin. Often the only choice is to use a pair of pliers to squeeze the contacts together again. The damage appears to have been caused by some off-brand 50 ohm terminators that require an unusual mount of force to seat on the connector. But the repair doesn't last. Once the female pin has been forced open, it quickly goes intermittent again. This is a big problem since the scope connector is usually a special item that is difficult to get. Regards, Mike Monett Article: 97512 of rec.radio.amateur.homebrew From: Paul Keinanen Subject: Re: Best Way to build a calibrated S meter Message-ID: <0fa972h8phc13p6vq6kqva3g9vg4rrhu6l@4ax.com> References: <44727d43$1_1@news.iprimus.com.au> <9m0672t4afp02rttvafmrgfa7k8k7aa35g@4ax.com> Date: Wed, 24 May 2006 23:20:43 +0300 On Tue, 23 May 2006 16:26:43 +0100, "Reg Edwards" wrote: >"Paul Keinanen" wrote in message >news:9m0672t4afp02rttvafmrgfa7k8k7aa35g@4ax.com... >> On Tue, 23 May 2006 12:16:27 +0100, "Reg Edwards" >> wrote: >> >> >Replace the meter scale with a white card and calibrate it yourself >> >with pen and ink. You will also need a signal generator and an >> >attenuator. >> >> If you derive the S-meter reading from the a.g.c. control voltage, be >> prepared to perform the calibration at various temperatures, since the >> gain of simple IF-strips vary with temperature (and thus need a >> different amount of a.g.c.), unless the gain is controlled by passive >> components only. >> >> With various front end filter for various frequency bands and >> attenuation depending of the frequency, you would have to perform the >> calibration on several frequencies. >> >> Instead of a pen and ink, it would be more practical to use a micro >> controller with sufficient non-volatile storage for the conversion >> tables and use analog inputs for a.g.c. voltage and temperature and >> some kind of input for the frequency being received. With these inputs >> and the conversion table, a voltage proportional of the log of the >> antenna terminal power could be generated. >> >> Paul OH3LWR >=========================================== > >I don't doubt that the problem is capable of being solved. >Just throw enough electronic hardware and software at it. >The cost can be estimated at 100,000 Euros. >The size and weight of the receiver will be quadrupled. >No amateur would be able to afford buying one. >American tax-payers would prevent NASA from doing the research and >development work. Even Bush would object. While NASA might have needed such sums in the 1960's, the functionality suggested above should be doable these days with any micro controller with a few kilobytes of non-volatile storage. While the frequency, power level and temperature calibration points might require a three dimensional array, in practice, it should be acceptable to get a few single dimensional vectors for each amateur band. One vector for a specific band might contain the front end frequency response for 5-10 frequencies within and around a band. Getting the a.g.c. setting for different power levels for a fixed station at three different temperatures (say +10, +20 and +30 C) or five for a mobile station (with additional values for, say -50 and +70 C) should be enough. A few kilobytes should be more than enough to get the sample points for interpolation. >As for me and most other amateurs, I'm quite happy with an S-meter >reading which puts signal strength reports in the right ball-park. >Very strong, very weak, or indifferent. Exchanging RS(T) reports is so stupid, so I try to avoid it. The only meaningful exchange would be to exchange the field strength (V/m) or the power density (W/mē) in order to study the propagation conditions. Even if we could reliably measure the antenna terminal voltage (e.g. in dBuV) or power (dBm), we still would have to measure the antenna efficiency and capture area to get any meaningful readings. Paul OH3LWR Article: 97513 of rec.radio.amateur.homebrew From: Roy Lewallen Subject: Re: Vector network analysis question Date: Wed, 24 May 2006 14:29:28 -0700 Message-ID: <1279k1sebg0l07e@corp.supernews.com> References: <1148251273.804190.221090@g10g2000cwb.googlegroups.com> <1148257742.429945.239100@i39g2000cwa.googlegroups.com> <1148289728.231197.223160@j55g2000cwa.googlegroups.com> <12740abn01cvg07@corp.supernews.com> <1148349960.688130.228200@i40g2000cwc.googlegroups.com> <1148376846.131725.149370@j55g2000cwa.googlegroups.com> <1148383854.891849.41040@j55g2000cwa.googlegroups.com> <1278v4fqbibh08d@corp.supernews.com> Mike Monett wrote: > > Hi Roy, > > There's lots of room for confusion. The Kings tool FAQ implies the > center contact diameter got smaller when the pin was redesigned and > the old crimp die set would not work: > . . . > However, another manufacturer claims their new 75 ohm hardware is > interchangeable with 50 ohm connectors: > . . . > If your junkbox is anything like mine, it may have stuff purchased > 20 years ago mixed with more recent purchases. So it might be > worthwhile to check carefully before mating different hardware. For sure. It looks like it's not safe to mate a 75 ohm connector with anything, even another 75 ohm connector, without checking pin diameter. Roy Lewallen, W7EL Article: 97515 of rec.radio.amateur.homebrew From: mcalhoun@ksu.edu Subject: Suggestions how to fix a 2-m xcvr problem? Date: 24 May 2006 18:07:48 -0500 Message-ID: NOTE: Crossposted to rec.radio.amateur.equipment and rec...homebrew. For some years, I've had a Kenwood TM-251A 2-meter xcvr (with 440 rcv) hanging from the ceiling of my pickup truck, and recently the TouchTone pad (in the microphone) quit working and, while PTT causes plenty of RF output, there's no AUDIO output. I'm pretty sure the problem is in the microphone electronics OR its 8-wire cord. I've "beeped" the cord from the telephone/data-like (RJ-45?) connector to solder joints on the mike PC board (it's quite a full little board!) and don't find anything wrong (but it's hard to hold a probe on each end and wiggle everything in the middle!). I'd replace the cord in a flash except I can't handle that %$#@! RJ connector. The only microphone detail in the xcvr Service Manual other than the connector pinout: UP +8 volts (I measued +7.25) GROUND PTT ME (Mike Earth?) MIKE RD (Read Detect? An output, perhaps for use with a TNC?) DOWN is the fact that PTT, UP, DOWN, CALL, VFO, MR, and PF are connected to three analog-inputs (and ground), thus "using up" four of the seven input wires and leaving just two wires (MIKE and ME) to handle the remaining 16 TouchTone keys AND audio! PTT, UP, DOWN, CALL, VFO, MR, and PF do work as they are supposed to. With "Remote Control Mode" ON, letter "A" on the TT pad is supposed to start frequency input from the keypad, but it does NOT. With an oscilloscope probe on the MIKE and ME wires, pushing "A" gives no visible change in the trace, but my jury-rig setup would probably miss a single tone-burst, so that is probably an inconclusive test other than the xcvr CPU didn't respond, either. Any suggestions? -- --Myron A. Calhoun. Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) Article: 97516 of rec.radio.amateur.homebrew Subject: Re: Vector network analysis question From: Mike Monett References: <1148251273.804190.221090@g10g2000cwb.googlegroups.com> <1148257742.429945.239100@i39g2000cwa.googlegroups.com> <1148289728.231197.223160@j55g2000cwa.googlegroups.com> <12740abn01cvg07@corp.supernews.com> <1148349960.688130.228200@i40g2000cwc.googlegroups.com> <1148376846.131725.149370@j55g2000cwa.googlegroups.com> <1148383854.891849.41040@j55g2000cwa.googlegroups.com> <1278v4fqbibh08d@corp.supernews.com> <1279k1sebg0l07e@corp.supernews.com> Message-ID: Date: Wed, 24 May 2006 19:56:42 -0400 Roy Lewallen wrote: > For sure. It looks like it's not safe to mate a 75 ohm connector with > anything, even another 75 ohm connector, without checking pin diameter. > > Roy Lewallen, W7EL Or even 50 ohms, for that matter. But how do you check the pin diameter on an existing connector? A caliper won't go in there. Also, the diameter could be correct but the pin could be assembled incorrectly and stick out too far. This will damage the female pin. Or maybe you know of some other non-destructive method to tell if you can mate an existing male and female coax connector without damage? The vulnerable part is the female pin. Once those legs get splayed there's no way to put them back. All it takes is one event to effectively ruin a brand-new scope. Regards, Mike Monett Article: 97517 of rec.radio.amateur.homebrew From: Roy Lewallen Subject: Re: Vector network analysis question Date: Wed, 24 May 2006 18:40:41 -0700 Message-ID: <127a2ous33lp5bb@corp.supernews.com> References: <1148251273.804190.221090@g10g2000cwb.googlegroups.com> <1148257742.429945.239100@i39g2000cwa.googlegroups.com> <1148289728.231197.223160@j55g2000cwa.googlegroups.com> <12740abn01cvg07@corp.supernews.com> <1148349960.688130.228200@i40g2000cwc.googlegroups.com> <1148376846.131725.149370@j55g2000cwa.googlegroups.com> <1148383854.891849.41040@j55g2000cwa.googlegroups.com> <1278v4fqbibh08d@corp.supernews.com> <1279k1sebg0l07e@corp.supernews.com> Mike Monett wrote: > Roy Lewallen wrote: > >> For sure. It looks like it's not safe to mate a 75 ohm connector with >> anything, even another 75 ohm connector, without checking pin diameter. >> >> Roy Lewallen, W7EL > > Or even 50 ohms, for that matter. But how do you check the pin diameter on > an existing connector? A caliper won't go in there. Also, the diameter > could be correct but the pin could be assembled incorrectly and stick out > too far. This will damage the female pin. > > Or maybe you know of some other non-destructive method to tell if you can > mate an existing male and female coax connector without damage? > > The vulnerable part is the female pin. Once those legs get splayed there's > no way to put them back. All it takes is one event to effectively ruin a > brand-new scope. Well, a scope will have a 50 ohm female connector, which should tolerate any kind of male without damage. The only vulnerable connector should be a 75 ohm female connector of the sort which has a smaller pin diameter. I don't believe I've ever seen one of those, and you'll certainly never see one on any commercial equipment except only possibly some video-related units. Roy Lewallen, W7EL Article: 97518 of rec.radio.amateur.homebrew From: Dr. Anton T. Squeegee Subject: Re: what's up with eham? Date: Wed, 24 May 2006 19:04:34 -0700 Message-ID: References: <1279c3alj3said0@corp.supernews.com> In article , gsm@mendelson.com (known to some as Geoffrey S. Mendelson) scribed... > Dave Platt wrote: > > > > Looks as if the server's off the air. > > Couldn't happen to nicer people in my opinion. When I complained that they > had Google ads on their site which directly supported BPL, the owner of the > site told me that BPL was an INTERNET technology and since his site was > RADIO related, it wasn't his concern. Sheesh... If the site comes back up, I'm yanking my account. I must not have seen the ads thanks to my ad blockers... > He also said that without Google ads, he could not keep the site alive, > so he choose Google and BPL. Fooey. There have to be other ads he can have up there without supporting a spectrum-destructive technology. -- Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute (Known to some as Bruce Lane, KC7GR) http://www.bluefeathertech.com -- kyrrin a/t bluefeathertech d-o=t calm "Salvadore Dali's computer has surreal ports..." Article: 97519 of rec.radio.amateur.homebrew Subject: Re: Vector network analysis question From: Mike Monett References: <1148251273.804190.221090@g10g2000cwb.googlegroups.com> <1148257742.429945.239100@i39g2000cwa.googlegroups.com> <1148289728.231197.223160@j55g2000cwa.googlegroups.com> <12740abn01cvg07@corp.supernews.com> <1148349960.688130.228200@i40g2000cwc.googlegroups.com> <1148376846.131725.149370@j55g2000cwa.googlegroups.com> <1148383854.891849.41040@j55g2000cwa.googlegroups.com> <1278v4fqbibh08d@corp.supernews.com> <1279k1sebg0l07e@corp.supernews.com> <127a2ous33lp5bb@corp.supernews.com> Message-ID: Date: Wed, 24 May 2006 22:54:43 -0400 Roy Lewallen wrote: > Well, a scope will have a 50 ohm female connector, which should > tolerate any kind of male without damage. That's what I was talking about earlier. I ruined the BNC inputs on some of my older TEK scopes by using off-brand 50 ohm terminators that were difficult to install. Apparently the male pin extended too far into the female and spread the pins. Some cheap commercial coax cable had the same problem. The scope bnc connectors are special and had the multiplier contact for 10X probes, and were too difficult and expensive to get and install. I would often waste time debugging strange waveforms when it turned out the problem was in the scope connector. Squeezing the pins gently would make it work for a while, then it would come right back. You often see the problem on used equipment like spectrum analyzers, sig generators and counters. Evidently someone went in with needlenose pliers to try to tighten the legs, but instead squashed them into a square instead of a circle. They don't make reliable connections after that. After discussing this, I'm inclined to get a handful of female connectors to test the male coax hardware. If it ruins the connector and cannot be fixed, toss it in the garbage where it belongs. > The only vulnerable connector should be a 75 ohm female connector > of the sort which has a smaller pin diameter. > I don't believe I've ever seen one of those, and you'll certainly > never see one on any commercial equipment except only possibly > some video-related units. That's good - I don't think I've ever used or seen any 75 ohm hardware, but maybe someone working on TV might run into the problem. > Roy Lewallen, W7EL Regards, Mike Monett Article: 97520 of rec.radio.amateur.homebrew Message-ID: <44751EA3.5010303@invalid.invalid> From: Doug Smith W9WI Subject: Re: Suggestions how to fix a 2-m xcvr problem? References: Date: Thu, 25 May 2006 03:04:04 GMT mcalhoun@ksu.edu wrote: > each end and wiggle everything in the middle!). I'd replace the cord in > a flash except I can't handle that %$#@! RJ connector. Look for a Cat5 computer LAN patch cable; cut off one end. It won't be coiled but it will be flexible & the plug will already be there for you. -- Doug Smith W9WI Pleasant View (Nashville), TN EM66 http://www.w9wi.com Article: 97521 of rec.radio.amateur.homebrew From: biascomms Subject: Re: Suggestions how to fix a 2-m xcvr problem? References: Message-ID: Date: Thu, 25 May 2006 06:16:08 GMT mcalhoun@ksu.edu wrote: > NOTE: Crossposted to rec.radio.amateur.equipment and rec...homebrew. > > For some years, I've had a Kenwood TM-251A 2-meter xcvr (with 440 rcv) > hanging from the ceiling of my pickup truck, and recently the TouchTone > pad (in the microphone) quit working and, while PTT causes plenty of RF > output, there's no AUDIO output. > > I'm pretty sure the problem is in the microphone electronics OR its > 8-wire cord. I've "beeped" the cord from the telephone/data-like (RJ-45?) > connector to solder joints on the mike PC board (it's quite a full little > board!) and don't find anything wrong (but it's hard to hold a probe on > each end and wiggle everything in the middle!). I'd replace the cord in > a flash except I can't handle that %$#@! RJ connector. > > The only microphone detail in the xcvr Service Manual other than the > connector pinout: > UP > +8 volts (I measued +7.25) > GROUND > PTT > ME (Mike Earth?) > MIKE > RD (Read Detect? An output, perhaps for use with a TNC?) > DOWN > is the fact that PTT, UP, DOWN, CALL, VFO, MR, and PF are connected to > three analog-inputs (and ground), thus "using up" four of the seven > input wires and leaving just two wires (MIKE and ME) to handle the > remaining 16 TouchTone keys AND audio! > > PTT, UP, DOWN, CALL, VFO, MR, and PF do work as they are supposed to. > > With "Remote Control Mode" ON, letter "A" on the TT pad is supposed > to start frequency input from the keypad, but it does NOT. With an > oscilloscope probe on the MIKE and ME wires, pushing "A" gives no > visible change in the trace, but my jury-rig setup would probably miss > a single tone-burst, so that is probably an inconclusive test other > than the xcvr CPU didn't respond, either. > > Any suggestions? > Have you checked at the rig end? I've had broken or intermittent connections to the mic socket - the socket pins have poor soldered joints. Bob -- Everything gets easier with practice, except getting up in the morning! Article: 97522 of rec.radio.amateur.homebrew Date: Thu, 25 May 2006 07:56:53 +0100 From: Will Subject: Flash Crystals Message-ID: <44755535$1_1@news.iprimus.com.au> Hi www.expandedspectrumsystems.com Anyone have one of these flash crystal units? Are they clean enough to use for receiver testing. I see no phase noise figures on their web page. Will Article: 97523 of rec.radio.amateur.homebrew From: "amdx" References: <1148089683.117088.14490@j73g2000cwa.googlegroups.com> Subject: Re: 5.0 - 5.5 mHz. VFO Date: Thu, 25 May 2006 06:06:59 -0500 Message-ID: <18fe2$44758fcd$45011502$27338@KNOLOGY.NET> "k9jri" wrote in message news:1148089683.117088.14490@j73g2000cwa.googlegroups.com... > I am looking for a contruction artical or some other starting point for > a solid state 5 to 5.5 mHz. VFO to use with my PSK-20. Hopefully > somebody can point me to a contruction project, a kit or a source of a > VFO. > QST June 1991 pg 27 has a VFO that does 5.0 to 5.5 mhz. The article is written by Doug Demaw. Article: 97524 of rec.radio.amateur.homebrew From: "Caveat Lector" References: <1279c3alj3said0@corp.supernews.com> Subject: Re: what's up with eham? Message-ID: Date: Thu, 25 May 2006 07:35:01 -0700 "Dr. Anton T. Squeegee" wrote in message news:MPG.1edeb092beb305489896a7@news.drizzle.com... > In article , gsm@mendelson.com > (known to some as Geoffrey S. Mendelson) scribed... > >> Dave Platt wrote: >> > >> > Looks as if the server's off the air. >> >> Couldn't happen to nicer people in my opinion. When I complained that >> they >> had Google ads on their site which directly supported BPL, the owner of >> the >> site told me that BPL was an INTERNET technology and since his site was >> RADIO related, it wasn't his concern. > > > > Sheesh... If the site comes back up, I'm yanking my account. I must > not have seen the ads thanks to my ad blockers... > >> He also said that without Google ads, he could not keep the site alive, >> so he choose Google and BPL. > > Fooey. There have to be other ads he can have up there without > supporting a spectrum-destructive technology. > > The website owner doesn't choose the ads to appear, Google does that automatically, based on keywords. But Google adSense has a filter option to trash any undesired ad. A simple matter to put the "offending" ad in the filter list. Eham has been a valuable resource for hams. With the high cost of running a Mega Site such as eham, I suggest we support the site, otherwise it may go away. You will notice a lot of the Ham Megasites are using Google AdSense. Why? It is bloody expensive to run a megasite. When the site gets popular, a "Normal" provider will add outrageous costs for excess bandwidth, forcing a web master to get a server. Servers ain't cheap. There are other costs as well, main provider, link checkers, domain name costs, computer maintenance, anti-virus checkers, software, etc.This says nothing about the Web Master's labor to keep the site running. Many of the mega sites are free - such a deal. AND - you buy a magazine -- full of ads, Movie rental - full of ads, cable TV - full of ads, etc. I suspect the ads income on Mega Sites don't come near the covering the cost of running a Mega Site. Even if it did, so what - you don't have to click on the ads or read them. Can't do that with magazines (;-) RE: The BPL ads -- maybe run your own Anti-BPL ad Huh -- CL -- I doubt, therefore I might be ! Article: 97525 of rec.radio.amateur.homebrew From: gsm@mendelson.com (Geoffrey S. Mendelson) Subject: Re: what's up with eham? Date: Thu, 25 May 2006 17:41:04 +0000 (UTC) Message-ID: References: <1279c3alj3said0@corp.supernews.com> Caveat Lector wrote: > RE: The BPL ads -- maybe run your own Anti-BPL ad Huh You miss the point. ALL Google ads are BPL adds. Google uses the money they get from Adsense to finance BPL networks. That's right, Google invested a lot of money in BPL. Using Adsense supports BPL, using Google supports BPL, buying Google stock supports BPL. Got it? Google and BPL are connected. As for supporting those sites, "you pays your money and you makes your choice". A click on a Google Adsense ad helps pay for BPL. There are other online "click here" advertising companies. He chose Google. I chose not to support him. IMHO it's like running a pro-enviornmentweb site and using the proceeds >from advertising to fund toxic waste dumping. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM IL Voice: (07)-7424-1667 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838 Visit my 'blog at http://geoffstechno.livejournal.com/