Article: 97353 of rec.radio.amateur.homebrew From: "Lynn Coffelt" Subject: Re: New program - PROPGATE: Coronation Street? Date: Sun, 7 May 2006 10:59:57 -0700 Message-ID: References: "Reg Edwards" wrote in message news:cuCdnc-NELohYsDZnZ2dnUVZ8qednZ2d@bt.com... > I never watch the tripe on Coronation Street. Who's Archie? Is he as > handsome as I am? > > Anyway, I wouldn't wish to correspond with anybody who regularly > watches Coronatio Street. They are clearly of low intelligence - the > submerged 20% of the population - with a concentratio span less than > the interval between the adverts. > Coronation Street still playing? Holy Cow! That was the best show on "tellie" when we were fortunate enough to live in England over 40 years ago! Salute! Old Chief Lynn Article: 97354 of rec.radio.amateur.homebrew From: "Harold E. Johnson" References: <1147024614.124022.27680@j73g2000cwa.googlegroups.com> Subject: Re: Quadrature Hybrid Construction Message-ID: Date: Sun, 07 May 2006 18:49:24 GMT "Radra" wrote in message news:1147024614.124022.27680@j73g2000cwa.googlegroups.com... >I need several quadrature hybrids (i.e. a 90 degree two-way splitter) > for use in portions of the 0.5 to 2.0 MHz band. This is for a > low-power phasing scheme. Normally I would obtain them from some place > like Mini-Circuit but some reason they only offer a 1.13 to 1.38 MHz > model (PSCQ-2-1.25). Can anyone suggest a source of supply? > MCL has them near all the way from DC to visible light. > Suppose I could also build them but am not familiar with the > construction techniques used at these low frequencies. Am more > accustomed to stripline and microstrip at VHF and UHF. Any suggestions > here would be appreciated. I am sure the techniques are well known and > must be covered in some articles, books and/or web sites. Reed Fisher, "Twisted-wire Quadrature Hybrid Directional Couplers". QST January 1978. pp 21-23. W4ZCB > Article: 97355 of rec.radio.amateur.homebrew From: "F4DRH" Subject: [QST] VHF amplifier push-pull 2c39 Date: Sun, 7 May 2006 22:36:16 +0200 Message-ID: <445e5a3e$0$6679$8fcfb975@news.wanadoo.fr> Hello all I am looking for information about a VHF amplifier with 2 X 2C39 in push-pull configuration (not in //). Does anybody know a website? ... or have a schematic? Thanks for your help Jean-Marc F4DRH www.barbaxoops.com Article: 97356 of rec.radio.amateur.homebrew From: Ken Scharf Subject: Re: [QST] VHF amplifier push-pull 2c39 References: <445e5a3e$0$6679$8fcfb975@news.wanadoo.fr> Message-ID: Date: Sun, 07 May 2006 16:52:19 -0400 F4DRH wrote: > Hello all > > I am looking for information about a VHF amplifier with 2 X 2C39 in > push-pull configuration (not in //). > Does anybody know a website? ... or have a schematic? > > Thanks for your help > > Jean-Marc > F4DRH > www.barbaxoops.com > > > The article you are looking for appeared in the Jan 1968 issue of QST and was reprinted in the 1972 HB. Maybe somebody has the 1965-1969 set of QST view? I have a copy of the 1972 HB, but it is quite yellowed and might not scan well. The schematic isn't going to do you much good since this is mostly a 'plumbers' and 'metal-smithing' problem. The article and the HB detail the cutting and bending of the metal (probably copper or brass as this beast must be soldered together). Also some springy finger stock is required to seal edges for rf and to contact the tube surfaces. Teflon is used to insulate parts and forms the dialectic for some capacitors. Mention is also made of beryllium copper. Be careful there, this stuff is deadly! Article: 97357 of rec.radio.amateur.homebrew From: Ken Scharf Subject: Re: [QST] VHF amplifier push-pull 2c39 References: <445e5a3e$0$6679$8fcfb975@news.wanadoo.fr> Message-ID: <88t7g.15479$Sl4.6523@bignews1.bellsouth.net> Date: Sun, 07 May 2006 16:54:39 -0400 F4DRH wrote: > Hello all > > I am looking for information about a VHF amplifier with 2 X 2C39 in > push-pull configuration (not in //). > Does anybody know a website? ... or have a schematic? > > Thanks for your help > > Jean-Marc > F4DRH > www.barbaxoops.com > > > oops. The article I mentioned was actually a PARALLEL amplifier, your post mentioned push pull. The article mentioned is for 1296mhz (not vhf) where these tubes are usually used. Article: 97358 of rec.radio.amateur.homebrew From: Ken Scharf Subject: Re: 13.8V high current power supply References: <1146323696.956339.201070@j73g2000cwa.googlegroups.com> <1146357642.620733.175050@y43g2000cwc.googlegroups.com> Message-ID: Date: Sun, 07 May 2006 17:33:48 -0400 Steve N. wrote: > wrote in message > news:1146357642.620733.175050@y43g2000cwc.googlegroups.com... > >>You're probably right! I did actually try to rip the heating element >>out of a 2kW electric fire to use as just such a test load, but the >>manufacturers had used some really devious sort of screw heads to keep >>the two casings together. :-( >>Failing some serious resistance wire, the only other 'to hand' option >>is to hook up the HF mobile and key-up; but I don't have a sufficiently >>gutsy dummy load or antenna to dump 100W into, I'm afraid. :-( >> > > > > Paul, > > Welcome to the world of design... > > > > No need to make a load to measure the ripple on the caps. You can > calculate it. I did this long ago for a 5V 28 amp supply I re-wound from a > 28V 5A supply. > > > > You have to know that for a capacitor, I = C * Dv / dt. > > When the 60 HZ wave drops, the diodes drop out of conduction and the filter > cap is now supplying *all* the load current...and the voltage drops in the > usual capacitive nature following that formula. > > I don't recall if you said the current, but...if you will be drawing, say 20 > amps - you have the "I". If you have a "C" you plan to use from the old > design, you have "C". Dt is the discharge time between the (full-wave) > peaks from the bridge rectifier. This is 8.333 ms. minus the conduction > time. I forget the typical conduction time I have seen, but I'll assume 5 > ms max-load (the diodes don't conduct very long, typically.and.and the peak > current is pretty high to boot!) -- leaving 3ms for the discharge time. > Then Dv is the ripple, or more accurately, the sag. Also, consider that the > peak voltage will be lower when loaded due to the transformer winding > resistance and diode drop and anything else in there. > Since this is a full wave rectifier if we had ideal diodes they would be conducting all the time (IE: one SET of diodes if a bridge or one diode if a "CT" type rectifier). Also we have a SINE wave output, but in a FW the negative cycle is flipped up. So your formulas don't reflect the varying duty cycle out of the rectifier (it's not ON 5 ms and off 3 ms, but goes from 0 to full voltage following a sine function). I guess you can use the RMS function to determine the "effective" on and off times, and your guess is probably ballpark enough to be correct. > > > So, solving for Dv. Dv = (I* dt ) / C > > > > If you wanted 20 amps and had 20,000 uF, You'd have (20*.005)/.02 or 3 > volts of sag. > > > > BUT! This assumes *normal* line voltage. If you DO measure as some of the > others suggest, remember that you'll be using whatever line voltage is at > the time. Consider when there is a brown out. Pick a low-line voltage, say > 105 volts and use THAT voltage, Or the ratio 105/120 and adjust your output > voltage number accordingly when calculating things. > > > > You have to make sure that *Everything* that you want to power from this > voltage has enough voltage at the low point; series pass & Driver & driver's > driver (perhaps the 723). > > > > Finally, what I did to keep the required overhead to a minimum and, as a > result, the dissipation in the series pass transistors lower (and guarantee > poorer brown-out protection, unfortunately), I *added* a few extra, lighter > gauge wire turns to the *OUTPUT* winding to supply the 723 and driver stuff. > Add the same number of turns to each side of the secondary (put one and > measure the volts-per-turn to figure out how many) and put a diode from both > of them (pointing to) to another smaller filter cap. This requires, of > course two more diodes and filter cap, but they're smaller. You also have > to watch the ripple in the same way. > > > > Hope this helps. Let me know @arrl.net > > > > 73, Steve, K9DCI > > > > > > > > Article: 97359 of rec.radio.amateur.homebrew Message-ID: <445E7F26.1000903@invalid.invalid> From: Doug Smith W9WI Subject: Re: 12 volt plate tubes References: <1147037164.671574.93340@i39g2000cwa.googlegroups.com> Date: Sun, 07 May 2006 23:13:43 GMT cornytheclown@hotmail.com wrote: > Anybody know any tubes...st or gt shape preferred that will work on 12 > volts plate voltage for small 1 tube regens...possibly a stage or two > of amplification also. > > I know there were automobile radio tubes made that didnt need vibrators > but dont know any numbers myself. I found regular plain old receiving tubes worked OK down to 18 volts on the plates - didn't have any convenient way of getting 12 at the time but I'll bet they would have worked. Audio power amps had REALLY low output but if you're building a 1-tube regen you're not driving a speaker anyway... -- Doug Smith W9WI Pleasant View (Nashville), TN EM66 http://www.w9wi.com Article: 97360 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: 12 volt plate tubes Message-ID: References: <1147037164.671574.93340@i39g2000cwa.googlegroups.com> Date: Sun, 07 May 2006 23:18:12 GMT On 7 May 2006 14:26:04 -0700, cornytheclown@hotmail.com wrote: >Anybody know any tubes...st or gt shape preferred that will work on 12 >volts plate voltage for small 1 tube regens...possibly a stage or two >of amplification also. > >I know there were automobile radio tubes made that didnt need vibrators >but dont know any numbers myself. All of fthe numbers I'm listing are 7pin miniature but are easily found. All are 12V filliment and 12V plate operation. Ther are similar older tubes of this type in octal bases but I've not seen any around. There is a really interesting two tube regen in November 2003 QST (reprints from ARRL, in CT). Penatodes 12CX6 12ek6 12af6 Heptodes/pentagrid converters 12ag6 12ad6 12FA6 Triode duo diode 12aj6 12el6 12fm6 12ae6 Tetrode audio driver (low power output 70mw) 12K5 Allison Article: 97361 of rec.radio.amateur.homebrew From: Wes Stewart Subject: Re: Need further info on network analysis terms... Date: Sun, 07 May 2006 16:41:09 -0700 Message-ID: References: <1146608069.454943.48830@u72g2000cwu.googlegroups.com> <1146637932.421410.288860@e56g2000cwe.googlegroups.com> <1147035370.757945.280840@i39g2000cwa.googlegroups.com> On 7 May 2006 13:56:10 -0700, paul@burridge8333.fsbusiness.co.uk wrote: >Okay, thanks all. >I've obtained proprietory 50 ohm loads and power splitters, so just >need to sort out the throughs, shorts and opens. The obvious question >now is: in respect of throughs and open and shorted terminations, is >the coax length of these relevant? I envisage making up N-type >connectors with say one inch long coax stubs for both open and short >unless there's some problem with this. Is the electrical length of the >coax relevant? Yes. No sense elaborating, you don't seem read the answers. Article: 97362 of rec.radio.amateur.homebrew Message-ID: <445EA281.7020502@nettally.com> From: **THE-RFI-EMI-GUY** Subject: Re: 12 volt plate tubes References: <1147037164.671574.93340@i39g2000cwa.googlegroups.com> Date: Mon, 08 May 2006 01:41:10 GMT I think some early Motorola auto radios worked off DC directly and had tubes in the RF and transistor audio PA's. You might look for some vintage auto radio schematics for tube numbers. I thing the 12AX7 tube might be included. cornytheclown@hotmail.com wrote: >Anybody know any tubes...st or gt shape preferred that will work on 12 >volts plate voltage for small 1 tube regens...possibly a stage or two >of amplification also. > >I know there were automobile radio tubes made that didnt need vibrators >but dont know any numbers myself. > > > -- Joe Leikhim K4SAT "The RFI-EMI-GUY"© "Treason doth never prosper: what's the reason? For if it prosper, none dare call it treason." "Follow The Money" ;-P Article: 97363 of rec.radio.amateur.homebrew From: "Heriberto" References: <1147037164.671574.93340@i39g2000cwa.googlegroups.com> Subject: Re: 12 volt plate tubes Message-ID: <445eb397_3@x-privat.org> Date: 8 May 2006 04:57:27 +0200 Hi: in this site have good information over space charge mode function in conventional tubes (no special for 12 v).- This mode permit work the tubes with low voltagfe in plate. http://www.duntemann.com/12vtubes/12vtubesindex.htm In the followings sites have a receiver projetc with 6BA6 tubes working with 12 V in plate.- http://www.qsl.net/kl7h/GlowBug.htm http://www.qsl.net/kl7h/12v.htm REgards from Argentina Heriberto LU6DBU escribió en el mensaje news:1147037164.671574.93340@i39g2000cwa.googlegroups.com... > Anybody know any tubes...st or gt shape preferred that will work on 12 > volts plate voltage for small 1 tube regens...possibly a stage or two > of amplification also. > > I know there were automobile radio tubes made that didnt need vibrators > but dont know any numbers myself. > Inviato da X-Privat.Org - Registrazione gratuita http://www.x-privat.org/join.php Article: 97364 of rec.radio.amateur.homebrew From: "Heriberto" References: <1147037164.671574.93340@i39g2000cwa.googlegroups.com> Subject: Re: 12 volt plate tubes Message-ID: <445eb462_2@x-privat.org> Date: 8 May 2006 05:00:50 +0200 hI: I forgoten this site also ; http://www.oldradios.co.nz/hikers/ Regards Heriberto LU6DBU escribió en el mensaje news:1147037164.671574.93340@i39g2000cwa.googlegroups.com... > Anybody know any tubes...st or gt shape preferred that will work on 12 > volts plate voltage for small 1 tube regens...possibly a stage or two > of amplification also. > > I know there were automobile radio tubes made that didnt need vibrators > but dont know any numbers myself. > Inviato da X-Privat.Org - Registrazione gratuita http://www.x-privat.org/join.php Article: 97365 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: 12 volt plate tubes Message-ID: References: <1147037164.671574.93340@i39g2000cwa.googlegroups.com> <445EA281.7020502@nettally.com> Date: Mon, 08 May 2006 03:03:22 GMT On Mon, 08 May 2006 01:41:10 GMT, **THE-RFI-EMI-GUY** wrote: >I think some early Motorola auto radios worked off DC directly and had >tubes in the RF and transistor audio PA's. You might look for some >vintage auto radio schematics for tube numbers. Correct and I listed some of the tubes used. Also Philco, and Delco had 12V tubes. Some call them space charge tubes. Typical line up was: 12ek6 RF, 12ad6 converter, 12ek6 IF and 12AE6 detector first audio, 12F6 audio driver and a DS501 as audio power. > I thing the 12AX7 tube might be included. No, that is a conventional tube. Though I've used it in a regen at 12V, it ran better at around 30-40V. Allison > >cornytheclown@hotmail.com wrote: > >>Anybody know any tubes...st or gt shape preferred that will work on 12 >>volts plate voltage for small 1 tube regens...possibly a stage or two >>of amplification also. >> >>I know there were automobile radio tubes made that didnt need vibrators >>but dont know any numbers myself. >> >> >> Article: 97366 of rec.radio.amateur.homebrew From: - exray - Subject: Re: 12 volt plate tubes Date: Sun, 07 May 2006 23:44:50 -0400 Message-ID: <125tfll15kmkd81@corp.supernews.com> References: <1147037164.671574.93340@i39g2000cwa.googlegroups.com> <445eb462_2@x-privat.org> Heriberto wrote: > hI: > I forgoten this site also ; > > http://www.oldradios.co.nz/hikers/ > > Regards > > Heriberto > LU6DBU I second this one. I've built 3 Hikers, bcb and sw...one is featured on the site...and they have been excellent rcvrs for low voltage. The later version using 3Q5s also works very well. -Bill Article: 97367 of rec.radio.amateur.homebrew From: Dave Hildebrand Subject: ICOM 02-AT QUESTION Date: Sun, 7 May 2006 21:31:05 -0700 Message-ID: I have a 22-year old Icom 02-AT that has worked reliably until now, when it ceased putting out any transmitter power whatsoever. Shall I assume the obvious, that the final (amplifier) transistor has blown? (They're easy enough to replace in most radios.) Or is there something else that's known to fail in these (particular) radios that results in a loss of transmitter power? And can anyone please tell me the part number of the power device used in the final amplifier? Thanx. ...Dave, N6BHU Article: 97368 of rec.radio.amateur.homebrew From: "steve carey" Subject: tubes Date: Mon, 8 May 2006 02:04:46 -0400 Message-ID: <445edf0b_1@newspeer2.tds.net> Looking 3B28 tubes does anybody have some in there junk box thanks Steve Article: 97369 of rec.radio.amateur.homebrew From: "Harold E. Johnson" References: <1147024614.124022.27680@j73g2000cwa.googlegroups.com> <1147055280.259058.17010@g10g2000cwb.googlegroups.com> <1147062688.747519.248140@g10g2000cwb.googlegroups.com> Subject: Re: Quadrature Hybrid Construction Message-ID: Date: Mon, 08 May 2006 09:49:59 GMT "Radra" wrote in message news:1147062688.747519.248140@g10g2000cwb.googlegroups.com... >I am willing to use several hybrids to cover the band, if I must. But > it would be helpful to use broadband hybrids so I don't need to use so > many. I appreciate the reference to the QST article on hybrid > construction. I will build one to see how much bandwidth I can get. > Would like to find a construction technique which yields wider > bandwidth tho. The PSCQ-2-32 from Mini-Circuits has a 3.2 to 32 MHz > bandwidth! Wonder how they do it. > > The LO technique is not applicable for my design but it is interesting. > I will have to give it some thought to understand how it works. > > Vinton Well, for that requirement, you need : G.W. Horn, I4MK, "How to design Wide-Band RF Quadrature Network" QEX, November 1982, pp5-9. 3-30 MHz quadrature networks designed by VE5FP/VK2BOX Rick Campbell, KK7B has "SPRAT Technical cartoons #1 and #2" that have details on single band hybrids, and the component values for them. > W4ZCB Article: 97370 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: 12 volt plate tubes Message-ID: <3oou52l247dihji9ocfuhnhlp6h4r3qu35@4ax.com> References: <1147037164.671574.93340@i39g2000cwa.googlegroups.com> <445eb462_2@x-privat.org> <125tfll15kmkd81@corp.supernews.com> Date: Mon, 08 May 2006 15:31:25 GMT On Sun, 07 May 2006 23:44:50 -0400, - exray - wrote: >Heriberto wrote: >> hI: >> I forgoten this site also ; >> >> http://www.oldradios.co.nz/hikers/ >> >> Regards >> >> Heriberto >> LU6DBU > >I second this one. I've built 3 Hikers, bcb and sw...one is featured on >the site...and they have been excellent rcvrs for low voltage. The >later version using 3Q5s also works very well. > >-Bill Over the years I done the regen thing many times using as may different devices as can be named. Thats a great site as some of the old schematics I'd used were lost and some cute designs are there. My favorite sets I've built use 12V space charge tubes12CX6 and 12AD6, 12ba6 and 12ad6 as a 12 volt only 20m to 80m converter and 1AD4 and 5678 (hearing aid tubes at 22.5V). Other oddball tubes I've built radios with use the 8056 and 6CW4 nuvisters for a superregen aircraft band rx. Allison Article: 97371 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: Quadrature Hybrid Construction Message-ID: References: <1147024614.124022.27680@j73g2000cwa.googlegroups.com> Date: Mon, 08 May 2006 15:39:10 GMT On 7 May 2006 10:56:54 -0700, "Radra" wrote: >I need several quadrature hybrids (i.e. a 90 degree two-way splitter) >for use in portions of the 0.5 to 2.0 MHz band. This is for a >low-power phasing scheme. Normally I would obtain them from some place >like Mini-Circuit but some reason they only offer a 1.13 to 1.38 MHz >model (PSCQ-2-1.25). Can anyone suggest a source of supply? > >Suppose I could also build them but am not familiar with the >construction techniques used at these low frequencies. Am more >accustomed to stripline and microstrip at VHF and UHF. Any suggestions >here would be appreciated. I am sure the techniques are well known and >must be covered in some articles, books and/or web sites. One approach that works and is simplet to build and test is a 90hybrid at a fixed frequency say 6mhz and downconvert both outputs using a variable osc at 6.5 to 8mhz. There result is a fixed phase difference and variable frequency in the .5mhz to 2mhz range. The downconversion is done using identical DBM and amplifiers so they add no phase shift differential. Advantage is any wide frequency range is doable and once set up will hold phase tracking well. Allison Article: 97372 of rec.radio.amateur.homebrew From: Straydog Subject: Re: 12 volt plate tubes Date: Mon, 8 May 2006 15:39:18 -0400 Message-ID: References: <1147037164.671574.93340@i39g2000cwa.googlegroups.com> FYI, The tubes designed to work on 12 v for the plate might be best, but there are a number of battery filament tubes that also migh give you some results. eg. 1L4,1T4,1U4,1R4,1R5, etc (all 7 pin miniatures). (there was a series of 8 pin octal tubes, too). Most of them ran filament voltages of 1.4 volts at 50 ma current. I built a audio oscilator with a 1T4 (pentode) as a kid and it would oscilate down to 7 volts on the plate!! Most of those tubes were designed for up to 90 v on the plate. Power audio tubes were like 3S4, 3Q4, 3A4, etc (which would run 3.0 v at 50 ma, or center taped filament at 1.4 v and 100 ma). The 3A4, pentode, as RF amplifier was good for something like 1/2 watt output or so, not bad for QRP and no transistors. There was an older series of battery fillament tubes, designed for lead acid cells (all were 2.0 v on filaments and not much amperage, either). You'll have to consult an older tube manual for those if you want to try them. ===== no change to below, included for reference and context ===== On Sun, 7 May 2006, cornytheclown@hotmail.com wrote: > Anybody know any tubes...st or gt shape preferred that will work on 12 > volts plate voltage for small 1 tube regens...possibly a stage or two > of amplification also. > > I know there were automobile radio tubes made that didnt need vibrators > but dont know any numbers myself. > > Article: 97373 of rec.radio.amateur.homebrew From: biascomms Subject: Re: 13.8V high current power supply - update References: <1147103416.176308.205570@y43g2000cwc.googlegroups.com> Message-ID: Date: Mon, 08 May 2006 19:56:57 GMT paul@burridge8333.fsbusiness.co.uk wrote: > Hi all and thanks again for all the responses. > > Well I had another 10 minutes to spare again today so took a different > secondary tapping to try to get more voltage headroom. Following that > tweak, I now have 25.5VDC available across the large electrolytics. > This is obviously plenty enough for 13.8VDC regulated; but is it now > *too* much to drop efficiently? > Thanks, > p. I find that about 19 to 20 Volts off-load is about ideal for 13.8 Volts output - if your unregulated voltage is much higher than that, you make a /lot/ of heat! If you're using a suitably rated transformer (so that the secondary voltage doesn't dip too much under load), 19 Volts gives ample headroom. A brief word of advice - if you're going to use a 723 type regulator (usually a good choice), be careful to RF-bypass the op-amp (inside the 723) and provide an over-voltage trip of some kind. It is sometimes possible for the 723 to suffer from "RF brain damage" and completely lose the plot if you get enough RF in the wrong places! The best over-voltage trip is really brutal - a high current thyristor to ground after a fuse in the unregulated DC rail driven by a simple transistor and zener comparator - if you get it right, you can get a large "thump" out of the blowing fuse! Bob -- Everything gets easier with practice, except getting up in the morning! Article: 97374 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: 12 volt plate tubes Message-ID: References: <1147037164.671574.93340@i39g2000cwa.googlegroups.com> Date: Mon, 08 May 2006 20:10:15 GMT On Mon, 8 May 2006 15:39:18 -0400, Straydog wrote: > >FYI, > >The tubes designed to work on 12 v for the plate might be best, but there >are a number of battery filament tubes that also migh give you some >results. eg. 1L4,1T4,1U4,1R4,1R5, etc (all 7 pin miniatures). (there was a >series of 8 pin octal tubes, too). Most of them ran filament voltages of >1.4 volts at 50 ma current. I built a audio oscilator with a 1T4 (pentode) >as a kid and it would oscilate down to 7 volts on the plate!! Most of those >tubes were designed for up to 90 v on the plate. Power audio tubes were like >3S4, 3Q4, 3A4, etc (which would run 3.0 v at 50 ma, or center taped filament >at 1.4 v and 100 ma). The 3A4, pentode, as RF amplifier was good for >something like 1/2 watt output or so, not bad for QRP and no transistors. Yep used them and the 3s4 is very happy with 18V (two 9v batteries) and makes a near optimum regen at 27V (three 9v batteries). I'd already mentioned the 1ad4 and 5678 these are hearing aid tubes that are very small with 1.4V 50ma filaments. They work very well with 22.5V so 18 to 27 V is both easy and work well for them. Common tubes like the 6ba6, and many of the other AA5 (6be6, 6ba6, 6av6 and they 12V versions) all work well at far less than 100V and save for the audio ouput tube (50C5) ran fine at 18V. For an oddball there is the 8058 a 12V nuvister that made a fine VHF osc, amp or mixer. >There was an older series of battery fillament tubes, designed for lead >acid cells (all were 2.0 v on filaments and not much amperage, either). >You'll have to consult an older tube manual for those if you want to try >them. Your thinking of #30, 31, 32 and 45. > >===== no change to below, included for reference and context ===== > >On Sun, 7 May 2006, cornytheclown@hotmail.com wrote: > >> Anybody know any tubes...st or gt shape preferred that will work on 12 >> volts plate voltage for small 1 tube regens...possibly a stage or two >> of amplification also. >> >> I know there were automobile radio tubes made that didnt need vibrators >> but dont know any numbers myself. >> >> Article: 97375 of rec.radio.amateur.homebrew From: "Steve N." Subject: Re: 13.8V high current power supply Date: Mon, 8 May 2006 15:27:25 -0500 Message-ID: References: <1146323696.956339.201070@j73g2000cwa.googlegroups.com> <1146357642.620733.175050@y43g2000cwc.googlegroups.com> "Ken Scharf" wrote in message news:RIt7g.38008$MM6.2351@bignews3.bellsouth.net... > That Steve N. wrote: > > Paul, > Welcome to the world of design... > > No need to make a load to measure the ripple on the caps. You can > > calculate it. ... > > You have to know that for a capacitor, I = C * Dv / dt. > > When the 60 HZ wave drops, the diodes drop out of conduction and the filter > > cap is now supplying *all* the load current...and the voltage drops in the > > usual capacitive nature following that formula.... Saying: > Since this is a full wave rectifier if we had ideal diodes they would be > conducting all the time (IE: one SET of diodes if a bridge or one diode > if a "CT" type rectifier). Ken, This is true only without the capacitor filter. When you add a capacitor input filter, the diodes (ideal or not) only conduct for a rather short part of the input cycle. Line current is in the form of rather short current pulses as a result. This is a concern for the power company, by the way. It also keeps the power company wave form rather flattened on the top, because of all the supplies on the grid drawing current only there. You can see and measure this on a supply if you have the capability. The cap will charge, pretty much to the peak. When the sine wave then drops rapidly toward zero, the caps "hold" that voltage and are now are supplying the load current. The voltage on the cap drops according to the formula. (the action of the regulator keeps the current at this point constant, so *THAT* formula applies) > Also we have a SINE wave output, Not once you add the capacitor input filter. You need the cap filter to (help) keep the output at the constant DC we desire. > but in a FW the negative cycle is flipped up. *** Yes and therefore you have 120, half cycles per second (in the US). That is 8.33 ms period (one peak every 8.33 ms). Draw a full wave rectified waveform, then plot some capacitor descharge on it and you will see that for a peak-to-peak ripple of, say, 10% the time the cap is charging is rather short. This is the diode conduction time. > So your formulas don't reflect the varying duty cycle out of the rectifier (it's not ON 5 ms and off 3 ms, I did mention that the diode conduction-angle duty-cycle does vary, but this is due to load current varrying - and it is predictable We only have 8.33 ms per pulse and the conduction angle is only 1-5 ms. depending on load. This *IS* the way linear supplies work. In theory and practice. That's why *that* formula works. If there was current in the diodes all the time, it would imply thta your capacitor filter ripple would be the full supply voltage. > but goes from 0 to full voltage following a sine function). Again, this is only without a capacitor input filter, if you refer to the output voltage. > I guess you can > use the RMS function to determine the "effective" on and off times, and No, this does not apply to this situation. RMS refers to the effective voltage, not diode conduction times. If you look at the *sine wave* waveform itself (full-wave rectified, in this case) then you can determine the charge and discharge waveforms and that is what I have described. If you can get a scope and do some real measurements for yourself, you'll see I am correct. For light loads on the power supply, the diode current pulses are quite short ~~ 1 ms and go only to around 5 with a heavy load. > your guess is probably ballpark enough to be correct. No guess here. What I described *is* the way it works. We do it when designing linear supplies all the time. You can see it with a scope. There are drawings on the web to show you what I tried to describe in words. I didn't read all of the following web pages, so one may be easier to understand than the others. The first shows *JUST* the rect waveform of which you speak: http://en.wikipedia.org/wiki/Rectifiers However, the rest of these show a capacitor input filter and the resulting waveforms and conduction characteristics I described. The following has a movie showing very well and slowly, how the "Smoothing" capacitor works: http://www.greenandwhite.net/~chbut/rectification.htm Ignore all the formulas in the following and about 2/3 of the way down are waveforms: http://www.visionics.ee/curriculum/Experiments/FW%20Rectifier/Full%20Wave%20Rectifier1.html Perhaps a simpler explanation: http://www.play-hookey.com/ac_theory/ps_filters.html I applaud your desire to help Paul's understanding, but you missed here. 73, Steve, K9DCI > > So, solving for Dv. Dv = (I* dt ) / C > > If you wanted 20 amps and had 20,000 uF, You'd have (20*.005)/.02 or 3 > > volts of sag. > > BUT! This assumes *normal* line voltage. If you DO measure as some of the > > others suggest, remember that you'll be using whatever line voltage is at > > the time. Consider when there is a brown out. Pick a low-line voltage, say > > 105 volts and use THAT voltage, Or the ratio 105/120 and adjust your output > > voltage number accordingly when calculating things. > > You have to make sure that *Everything* that you want to power from this > > voltage has enough voltage at the low point; series pass & Driver & driver's > > driver (perhaps the 723). > > Finally, what I did to keep the required overhead to a minimum and, as a > > result, the dissipation in the series pass transistors lower (and guarantee > > poorer brown-out protection, unfortunately), I *added* a few extra, lighter > > gauge wire turns to the *OUTPUT* winding to supply the 723 and driver stuff. > > Add the same number of turns to each side of the secondary (put one and > > measure the volts-per-turn to figure out how many) and put a diode from both > > of them (pointing to) to another smaller filter cap. This requires, of > > course two more diodes and filter cap, but they're smaller. You also have > > to watch the ripple in the same way. > > Hope this helps. Let me know @arrl.net > > 73, Steve, K9DCI Article: 97376 of rec.radio.amateur.homebrew From: Straydog Subject: Re: 12 volt plate tubes Date: Mon, 8 May 2006 20:19:05 -0400 Message-ID: References: <1147037164.671574.93340@i39g2000cwa.googlegroups.com> See down a bit.... On Mon, 8 May 2006, Allisonnospam@nouce.bellatlantic.net wrote: > On Mon, 8 May 2006 15:39:18 -0400, Straydog wrote: > >> >> FYI, >> >> The tubes designed to work on 12 v for the plate might be best, but there >> are a number of battery filament tubes that also migh give you some >> results. eg. 1L4,1T4,1U4,1R4,1R5, etc (all 7 pin miniatures). (there was a >> series of 8 pin octal tubes, too). Most of them ran filament voltages of >> 1.4 volts at 50 ma current. I built a audio oscilator with a 1T4 (pentode) >> as a kid and it would oscilate down to 7 volts on the plate!! Most of those >> tubes were designed for up to 90 v on the plate. Power audio tubes were like >> 3S4, 3Q4, 3A4, etc (which would run 3.0 v at 50 ma, or center taped filament >> at 1.4 v and 100 ma). The 3A4, pentode, as RF amplifier was good for >> something like 1/2 watt output or so, not bad for QRP and no transistors. > > Yep used them and the 3s4 is very happy with 18V (two 9v batteries) > and makes a near optimum regen at 27V (three 9v batteries). > > I'd already mentioned the 1ad4 and 5678 these are hearing aid tubes > that are very small with 1.4V 50ma filaments. They work very well > with 22.5V so 18 to 27 V is both easy and work well for them. > > Common tubes like the 6ba6, and many of the other AA5 (6be6, 6ba6, > 6av6 and they 12V versions) all work well at far less than 100V and > save for the audio ouput tube (50C5) ran fine at 18V. > > For an oddball there is the 8058 a 12V nuvister that made a fine > VHF osc, amp or mixer. > >> There was an older series of battery fillament tubes, designed for lead >> acid cells (all were 2.0 v on filaments and not much amperage, either). >> You'll have to consult an older tube manual for those if you want to try >> them. > > Your thinking of #30, 31, 32 and 45. Nah, don't have to go back that far. I got a RCA tube manual copyright 1960, and it shows, for example, 1D5-GP, 1G5-GT, 1D7-G, 1E7-GT, 1F4, 1F5-G, 1F6 as all 2.0 volt filament tubes, and most of them are octal bases, and one or two are 5 or 6 pin non-octals. And, I also know there were a couple numbers not made by RCA, but I spend most of my time with my nose in the RCA manual. And, I'm having a lot of fun in my early retirement years building a whole (retro) tube station from partly the junkbox, partly surplus, partly new, partly Radio Shack parts. But, I didn't know too much about the 12 v plate tubes although I knew they existed. So, after this year's recent posts, I started looking up the 12??blah-blah numbers in that tube manual and there is a lot there. Now gotta decide if I want to go that route or stay with the 1L4, 1R5, 1U4, 1T4, etc., route or use 6.3 v fil-cathode tubes with 100-200 v on plate. Part of me likes the idea of octal tube bases because they are so much easier to put into and take out of sockets (because of the keyed pin). Couple times in my life I dinged up pins on miniature tubes because I didn't look carefully at the pins on the tubes and the holes on the socket to line them up. Seems neater to have the keyed post; just aim the center of the post for the big hole, and then spin it around till it pops in. :-) 1.4 v filament tubes wouldn't throw a lot of heat in the summer time, either. If I built both kinds of rigs/receivers, I guess I could use the "hot" rig in the winter as extra heat for the room. And, the "cool" rig in the summer. ;-) Thanks for your comments, otherwise. ===== no change to below, included for reference and context ===== > >> >> ===== no change to below, included for reference and context ===== >> >> On Sun, 7 May 2006, cornytheclown@hotmail.com wrote: >> >>> Anybody know any tubes...st or gt shape preferred that will work on 12 >>> volts plate voltage for small 1 tube regens...possibly a stage or two >>> of amplification also. >>> >>> I know there were automobile radio tubes made that didnt need vibrators >>> but dont know any numbers myself. >>> >>> > > Article: 97377 of rec.radio.amateur.homebrew From: Dr. Anton T. Squeegee Subject: Re: RS-232 Rf module Date: Mon, 8 May 2006 20:28:47 -0700 Message-ID: References: <1147117593.825426.287010@j33g2000cwa.googlegroups.com> In article <1147117593.825426.287010@j33g2000cwa.googlegroups.com>, aymmmm@gmail.com (known to some as ayman) scribed... > hi, > I am working on an FPGA project. > It is a CDMA-based point-to-point communication system; two FPGAs each > works as a transceiver. > The final stage of the project is to send the data via the serial port > (RS-232) to an RF module. > Can any one support me a low-cost, serial (RS-232) Rf module capable of > managing data rates up to 1.25 Mb/s and working reliably within > buildings giving a suitable range ( >10 meters). With that high of a data rate, I wouldn't use RS232. You'd be better off with V.35 or perhaps RS485. Happy tweaking. -- 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: 97378 of rec.radio.amateur.homebrew From: "Tom Holden" References: <1147117593.825426.287010@j33g2000cwa.googlegroups.com> Subject: Re: RS-232 Rf module Message-ID: <13U7g.2647$aq5.132155@news20.bellglobal.com> Date: Mon, 8 May 2006 23:32:12 -0400 "ayman" wrote in message news:1147117593.825426.287010@j33g2000cwa.googlegroups.com... > hi, > I am working on an FPGA project. > It is a CDMA-based point-to-point communication system; two FPGAs each > works as a transceiver. > The final stage of the project is to send the data via the serial port > (RS-232) to an RF module. > Can any one support me a low-cost, serial (RS-232) Rf module capable of > managing data rates up to 1.25 Mb/s and working reliably within > buildings giving a suitable range ( >10 meters). > Pretty demanding requirement. RS-232 at 1.25 Mb/s? I thought RS-232 topped out at 115200 or 230400 bps? That's the max you'll see for commercial RS-232 RF Modems, e.g., http://www.maxstream.net/, and they list in the low $hundreds per end. Another approach is to use a serial device server, http://www.neteon.net/cat.aspx?clvl=3&c1=1&c2=3&c3=13, connected to a Wi-Fi network. Similar caps on serial speed, although one model claims 921.6 kbps max, the SSE-100. Tom Article: 97379 of rec.radio.amateur.homebrew From: "Harold E. Johnson" References: <1147024614.124022.27680@j73g2000cwa.googlegroups.com> <1147055280.259058.17010@g10g2000cwb.googlegroups.com> <1147062688.747519.248140@g10g2000cwb.googlegroups.com> Subject: Re: Quadrature Hybrid Construction Message-ID: Date: Tue, 09 May 2006 11:51:35 GMT Radra, unable to contact you off group. GM. I realize my reference is getting pretty old and may be difficult to obtain. If you'd like a .PDF of I4MK's 3-30 MHz quadrature 1982 article, I could send it to you, although it's a fairly large file. Conversely, he's still up and about and seems to be good in the QRZ call book. His article yields the equations for a hybrid for any frequency and should (I think) give you a single solution for your needs. Regards W4ZCB Article: 97380 of rec.radio.amateur.homebrew From: "clfe" References: Subject: Re: ICOM 02-AT QUESTION Date: Tue, 9 May 2006 10:48:15 -0400 Message-ID: <4460ab9c$0$3697$ecde5a14@news.coretel.net> "Bert Hyman" wrote in message news:Xns97BE60118855DVeebleFetzer@127.0.0.1... > clifto@gmail.com (clifto) wrote in > news:f7k6j3-5g8.ln1@remote.clifto.com: > >> Chuck Harris wrote: >>> The usual way of blowing the output transistor in an 02AT is to >>> use a battery pack that supplies more than 9v, or to try and power >>> the rig directly from your car battery. ISTR that a short on the >>> antenna is a third way. >> >> I ran mine off the car battery reliably for years. Go figure. > > Maybe the OP was thinking of the older IC-2A. One of the battery > packs for the 2A had a jack for connecting 12V to it, which allowed > you to run the radio off the battery while it was being charged. > Applying 12V directly to the radio (only possible by removing the > battery pack) would fry it. > > The IC-02A could run off 12-15V directly through a jack in the top > plate. > > -- > Bert Hyman | St. Paul, MN | bert@iphouse.com At the risk of going off topic, I recall someone mentioning that the RS 2 meter portable had an issue almost the same. The jack at the top was "supposed" to be for "vehicular" power - but I heard horror stories of the radio suffering damage when used in just that fashion. IAnd I've seen first hand - a battery pack that got smoked using vehicular power. It almost caught the guy's car on fire since it was near "cloth". I haven't looked at either the radio or schematic for so long - I can't recall exactly what the make-up is. I have though - heard many tales of guys blowing out radios in a vehicle. Hell, our Fire Department Squad Truck radio went out twice in 3 months from similar issues. I'm not sure if they actually figured out the exact reason as yet - Motorola and the original installer were to look over the situation. Seems to me, we all need to take an extra step to prevent such things from happening, since we can't rely on the manufacturers to do so. Just my 2 cents. clfe Article: 97381 of rec.radio.amateur.homebrew From: Bill Turner Subject: Re: 12 volt plate tubes Date: Tue, 09 May 2006 08:45:55 -0700 Message-ID: <40e162de3c1bscln4uncoaa90bvfgnkmsk@4ax.com> References: <1147037164.671574.93340@i39g2000cwa.googlegroups.com> ORIGINAL MESSAGE: On 7 May 2006 14:26:04 -0700, cornytheclown@hotmail.com wrote: >Anybody know any tubes...st or gt shape preferred that will work on 12 >volts plate voltage for small 1 tube regens...possibly a stage or two >of amplification also. > >I know there were automobile radio tubes made that didnt need vibrators >but dont know any numbers myself. *********** REPLY SEPARATOR *********** My first job right out of high school in 1959 was repairing car radios, just when the 12-volt anode tubes were coming out. On a whim, I replaced some of the 12-volt anode types with conventional tubes such as the 12AU6 and 12BA6 and to my surprise, they worked fairly well, but with slightly lower gain. (The pin connections were the same.) BTW, the 12-volt anode types were notorious for developing microphonics. It was an interesting design, but as soon as good transistors became available, they became history. In other words, don't be afraid to experiment. Bill, W6WRT Article: 97382 of rec.radio.amateur.homebrew From: ehramm@dk3uz.ampr.org (Edmund H. Ramm) Subject: Re: 12 volt plate tubes References: <1147037164.671574.93340@i39g2000cwa.googlegroups.com> Message-ID: Date: Tue, 9 May 2006 17:04:57 GMT In <1147037164.671574.93340@i39g2000cwa.googlegroups.com> cornytheclown@hotmail.com writes: > Anybody know any tubes...st or gt shape preferred that will work on 12 > volts plate voltage for small 1 tube regens...possibly a stage or two > of amplification also. > [...] 6DR8, 6GM8, 6DS8, 6ES6, 6ET6. 73, Eddi ._._. -- e-mail: dk3uz AT darc DOT de | AMPRNET: dk3uz@db0hht.ampr.org If replying to a Usenet article, please use above e-mail address. Linux/m68k, the best U**x ever to hit an Atari! Article: 97383 of rec.radio.amateur.homebrew From: dplatt@radagast.org (Dave Platt) Subject: Re: ICOM 02-AT QUESTION Date: Tue, 09 May 2006 18:21:04 -0000 Message-ID: <1261ncgn2e0c362@corp.supernews.com> References: <4460ab9c$0$3697$ecde5a14@news.coretel.net> In article <4460ab9c$0$3697$ecde5a14@news.coretel.net>, clfe wrote: >At the risk of going off topic, I recall someone mentioning that the RS 2 >meter portable had an issue almost the same. The jack at the top was >"supposed" to be for "vehicular" power - but I heard horror stories of the >radio suffering damage when used in just that fashion. IAnd I've seen first >hand - a battery pack that got smoked using vehicular power. It almost >caught the guy's car on fire since it was near "cloth". I haven't looked at >either the radio or schematic for so long - I can't recall exactly what the >make-up is. I have though - heard many tales of guys blowing out radios in a >vehicle. Hell, our Fire Department Squad Truck radio went out twice in 3 >months from similar issues. I'm not sure if they actually figured out the >exact reason as yet - Motorola and the original installer were to look over >the situation. Seems to me, we all need to take an extra step to prevent >such things from happening, since we can't rely on the manufacturers to do >so. Just my 2 cents. It would not surprise me much if the failures were due to a "load dump" event. If the alternator is running, and supplying a substantial amount of current to a load (e.g. headlights), and the load is suddenly disconnected (e.g. headlights turned off), it's not at all uncommon for a very impressive voltage spike to be generated. This is due to the same sort of inductive "kickback" which can occur when shutting off the drive current to a motor or relay or solenoid. My recollection is that the standard used in the automotive industry, is that electronic devices on a "12-volt" automobile bus should be designed to survive load-dump spikes of up to 50 volts. A radio designed for 12 (or 13.8) volt operation, whose finals are fed fairly directly from the battery supply, may work just fine if the ignition is off, but could easily fail on its first load-dump event. Some sort of fast-acting zener protection, followed by an RF choke, would probably be a good idea when connecting such radios to an automotive power system. Unfortunately, a 50-volt load-dump spike could exceed the input- to-output voltage-differential limit of common regulators such as an LM317; hence, even if you're using a regulator of this sort to power a radio intended for 9 volts, you'll probably need an upstream zener to keep the regulator from popping. -- 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: 97384 of rec.radio.amateur.homebrew From: Dunkirk Subject: Re: ICOM 02-AT QUESTION Date: Tue, 09 May 2006 11:10:03 -0700 Message-ID: <4460DAFB.1000105@ispwest.com> References: Hi, Chuck -- thanks for your response... Chuck Harris wrote: > Dave Hildebrand wrote: >> I have a 22-year old Icom 02-AT that has worked reliably until now, when >> it ceased putting out any transmitter power whatsoever. > > Does it still receive correctly? ...yes -- the only thing that's changed is that the little bar-graph (along the bottom) doesn't appear; as though there were nothing to be measured. And, I fell out of the repeater while in QSO (full-quieting), having to sign clear on another radio. > What usually happens, is the synthesizer quits, and it stops sending, > or receiving. ...in my case, I can dial-up any repeater and listen -- I just can't transmit any more. > The output transistor is a T05 (TO39) type package, and is soldered to the > metal frame that surrounds the radio. It is very special, in that the case > of the transistor is connected to the emitter. Most transistors in that > package have the case connected to the collector. This is done so that > they > could run the emitter grounded (as is usual) and not need any insulated > heatsinking hardware. ...are they (the transistors) a real bitch to replace? > The usual way of blowing the output transistor in an 02AT is to use a > battery > pack that supplies more than 9v, or to try and power the rig directly from > your car battery. ISTR that a short on the antenna is a third way. ...the jack on the top's supposed to have an internal regulator, and I've used it in my truck on occasion since the radio was new with no negative consequences (not like the HTX-202, which was made by Maxon under license by Icom for Radio Schlock, and had issues with its external power-jack). Maybe infrequent long-winded transmissions over the last 22 years is the culprit for the transmitter's untimely demise? (It's kept my hands warm in the cool outdoors more than once.) I've long since misplaced (or lost) the original manual, which had a schematic. If I crack it open, I should be able to measure the voltages on the device, itself to see if it's blown. Right now, the final seems like the prime suspect. Thanx... ...Dave, N6BHU Article: 97385 of rec.radio.amateur.homebrew From: Dunkirk Subject: Re: ICOM 02-AT QUESTION Date: Tue, 09 May 2006 11:16:53 -0700 Message-ID: <4460DC95.5020407@ispwest.com> References: <4460ab9c$0$3697$ecde5a14@news.coretel.net> Yeah, I've had a few experiences myself, in years past that taught me there's no such thing as too many fuses. My glove-compartment has an assortment of fuses of varying vintages, all acquired for that "rainy day" that some times never comes. Chuck Harris wrote: > clfe wrote: > >> At the risk of going off topic, I recall someone mentioning that the >> RS 2 meter portable had an issue almost the same. The jack at the top >> was "supposed" to be for "vehicular" power - but I heard horror >> stories of the radio suffering damage when used in just that fashion. > > I had a 2AT battery pack catch fire when charging off of the car charger. > There was no fuse in the power cord, and a wire shorted inside the pack. > Poof! It ate the wires inside of the pack, and the power cord all the > way back to the lighter outlet. A fuse would have been a *really good > thing*. > > -Chuck Article: 97386 of rec.radio.amateur.homebrew From: Dunkirk Subject: Re: ICOM 02-AT QUESTION Date: Tue, 09 May 2006 11:54:08 -0700 Message-ID: <4460E550.7010305@ispwest.com> References: <4460ab9c$0$3697$ecde5a14@news.coretel.net> <1261ncgn2e0c362@corp.supernews.com> Very (perhaps highly) plausible theory -- it's too bad that Icom didn't learn from Motorola, and create an inexpensive (relatively to their radio, anyway) vehicular charger for their radios (e.g. 'Convertacom'), rather than a (potential) built-in self-destruct device. Dave Platt wrote: > In article <4460ab9c$0$3697$ecde5a14@news.coretel.net>, > clfe wrote: > >> At the risk of going off topic, I recall someone mentioning that the RS 2 >> meter portable had an issue almost the same. The jack at the top was >> "supposed" to be for "vehicular" power - but I heard horror stories of the >> radio suffering damage when used in just that fashion. IAnd I've seen first >> hand - a battery pack that got smoked using vehicular power. It almost >> caught the guy's car on fire since it was near "cloth". I haven't looked at >> either the radio or schematic for so long - I can't recall exactly what the >> make-up is. I have though - heard many tales of guys blowing out radios in a >> vehicle. Hell, our Fire Department Squad Truck radio went out twice in 3 >> months from similar issues. I'm not sure if they actually figured out the >> exact reason as yet - Motorola and the original installer were to look over >> the situation. Seems to me, we all need to take an extra step to prevent >> such things from happening, since we can't rely on the manufacturers to do >> so. Just my 2 cents. > > It would not surprise me much if the failures were due to a "load > dump" event. > > If the alternator is running, and supplying a substantial amount of > current to a load (e.g. headlights), and the load is suddenly > disconnected (e.g. headlights turned off), it's not at all uncommon > for a very impressive voltage spike to be generated. This is due to > the same sort of inductive "kickback" which can occur when shutting > off the drive current to a motor or relay or solenoid. > > My recollection is that the standard used in the automotive industry, > is that electronic devices on a "12-volt" automobile bus should be > designed to survive load-dump spikes of up to 50 volts. A radio > designed for 12 (or 13.8) volt operation, whose finals are fed > fairly directly from the battery supply, may work just fine if the > ignition is off, but could easily fail on its first load-dump event. > > Some sort of fast-acting zener protection, followed by an RF choke, > would probably be a good idea when connecting such radios to an > automotive power system. > > Unfortunately, a 50-volt load-dump spike could exceed the input- > to-output voltage-differential limit of common regulators such as an > LM317; hence, even if you're using a regulator of this sort to power a > radio intended for 9 volts, you'll probably need an upstream zener to > keep the regulator from popping. > Article: 97387 of rec.radio.amateur.homebrew From: "Clair J. Robinson" Subject: Re: 12 volt plate tubes Date: Tue, 09 May 2006 20:47:30 -0500 Message-ID: <1262hhjo5oa3l98@corp.supernews.com> References: <1147037164.671574.93340@i39g2000cwa.googlegroups.com> cornytheclown@hotmail.com wrote: > Anybody know any tubes...st or gt shape preferred that will work on 12 > volts plate voltage for small 1 tube regens...possibly a stage or two > of amplification also. > > I know there were automobile radio tubes made that didnt need vibrators > but dont know any numbers myself. > In desperation, I once wired the triode section of a 6U8 into an oscillator circuit that had been designed for one of those 12v space charge tubes. It worked that one time, anyway. I was replacing a pair of "VHF Triode-Pentode" tubes by Sylvania (I don't remember the type number) in an FM to AM auto radio converter whose performance really sucked. The other three stages were fairly easily re-wired to work off an external 250v supply, but the oscillator didn't look promising. The effort was a success. I think I at least tripled the distance from the stations at which I could hear them. 73, CJ KØCJ Article: 97388 of rec.radio.amateur.homebrew From: Bill Turner Subject: Re: 12 volt plate tubes Date: Tue, 09 May 2006 19:04:48 -0700 Message-ID: References: <1147037164.671574.93340@i39g2000cwa.googlegroups.com> <1262hhjo5oa3l98@corp.supernews.com> ORIGINAL MESSAGE: On Tue, 09 May 2006 20:47:30 -0500, "Clair J. Robinson" wrote: >In desperation, I once wired the triode section of a 6U8 into an >oscillator circuit that had been designed for one of those 12v space >charge tubes. It worked that one time, anyway. *********** REPLY SEPARATOR *********** That reminds me of a fun thing to do when you have too much time on your hands. Design a tube type oscillator that will work on extremely low plate voltage. How low can you go? 12 volts is easy. How about three volts? Or one? Or less? I'd be interested to hear. Bill, W6WRT Article: 97389 of rec.radio.amateur.homebrew From: ricknj10@hotmail.com (Rick) Subject: Re: VFO output power Message-ID: <4461f8d7.1654046@news.optonline.net> References: <1147241561.722283.227940@g10g2000cwb.googlegroups.com> Date: Wed, 10 May 2006 14:32:46 GMT It is a good idea to build a buffer amplifier after the vfo. If you get more than +7 dbm build a little attenuator between the amplifier and the mixer. That way you get the right amount of drive, a stable load for the vfo, a resistive load for the mixer. If you want to spare the time, you can send me the vfo and I will look at it on a spectrum analyzer for you and also tell you accurate power level into 50 ohms. I am in NJ. Rick K2XT Article: 97390 of rec.radio.amateur.homebrew From: Joerg Subject: Re: Need further info on network analysis terms... References: <1146608069.454943.48830@u72g2000cwu.googlegroups.com> <1147076843.058679.321530@i40g2000cwc.googlegroups.com> <1147279037.027876.172520@j33g2000cwa.googlegroups.com> Message-ID: <6Mp8g.70440$F_3.43303@newssvr29.news.prodigy.net> Date: Wed, 10 May 2006 17:53:06 GMT Hello Paul, > Okay, so I think it's overwhelmingly clear that adding or subtracting > any electrical length from this "baseline" - (or "reference plain" as I > think it's also called) introduces measurement error which must be > allowed for/accounted for in some way to maintain accuracy. > Depends on how much you are talking about. Man often only needs this much precision ;-) > Let's say I make up a short and an open using N-type plugs as described > elsewhere on this thread, using identical, high quality plugs. Can I > then use these with my proprietory Suhner 50 Ohm precision N-type load > by calibrating out any differences between the home-made jobs and the > proprietory one? Let me describe what the three cal devices look like that came with our HP4191A (after all, this is the stuff that Hewlett-Packard has deemed acceptable): The "Short" is a flat nut with a closed end. It puts a flat plate directly across the face of the DUT connector. No length there. The "Open" is a longer threaded tube with a hollow inside, about an inch or so long and closed off at the far end. The "50 Ohm" is something I wasn't able to open w/o special tools but will some day. It looks like the resistor is about 1/2" to 3/4" up there >from the DUT connector surface, firmly encapsulated. All gold-plated, of course. > Further, I now know that a "through" is simply that U-shaped patch lead > that's often seen sticking out of the front of VNAs in catalogue > pictures. I also know that you can't make one of these with zero coax > length for obvious reasons. Given the fact then that it has an > unavoidable length; does it have to be any *specific* length in > relation to the open, short and 50 ohm terminations? The HP4191A has that, too. It needs to match the length that makes the DUT and ref path equal. The one on the HP4191A is about 1-1/2" for a zero length on the DUT. In order for the analyzer to be useful in settings where the DUT has to be a bit remote, like in a vacuum chamber, you can remove a little face plate, remove the "through" and install your own longer "through". It's made from rigid coax. Regards, Joerg http://www.analogconsultants.com Article: 97391 of rec.radio.amateur.homebrew From: "Steve N." Subject: Re: 13.8V high current power supply - update Date: Wed, 10 May 2006 16:25:20 -0500 Message-ID: References: <1147103416.176308.205570@y43g2000cwc.googlegroups.com> <1147280376.352051.67700@j73g2000cwa.googlegroups.com> One is that to properly fuse it, you can't have an excessive in-russ, or you'll need a really big fuse and it might be too big to protect the smoke hinside. Another is that you reqally don't want to pound either the diodes or the filter caps if you don't have to. 73, Steve, K9DCI wrote in message news:1147280376.352051.67700@j73g2000cwa.googlegroups.com... > Interesting. There are all sorts of protections one can build into PSUs > of course and it's a job to know where to stop with some of them. I'm > just wondering why there's a need to limit this inrush current. What is > it you're seeking to protect here? > Article: 97392 of rec.radio.amateur.homebrew From: "Steve N." Subject: Re: 13.8V high current power supply - update Date: Wed, 10 May 2006 16:26:55 -0500 Message-ID: References: <1147103416.176308.205570@y43g2000cwc.googlegroups.com> <1147105641.842995.48270@v46g2000cwv.googlegroups.com> <1147120682.398787.7640@v46g2000cwv.googlegroups.com> <1147282370.003175.163900@g10g2000cwb.googlegroups.com> Paul, If you didn't understand where I was going, Tim's is a good summary of my original post. 73, Steve, K9DCI "Tim Shoppa" wrote in message news:1147282370.003175.163900@g10g2000cwb.googlegroups.com... > paul@burridge8333.fsbusiness.co.uk wrote: > > Yes sorry, Tim. I should have mentioned that the 25.5VDC is the > > open-circuit voltage across the caps. > > I assume this new drop is do-able because this PSU in its original > > configuration provided 24VDC regulated from 40VDC unreg across the > > caps. That seemed like a hell of a drop without generating heaps of > > heat, but I freely admit my recollection of linear PSU design (like a > > lot of other electronics-related stuff) is very, very hazy. > > A MUCH more relevant number would be the average DC voltage and minimum > DC voltage across the caps under pretty much full load. > > A good dummy load for an unregulated supply is auto bulbs/headlamps in > series/parallel as appropriate. > > The average DC voltage under full load is very relevant to overall heat > dissipation. > > The minimum DC voltage (that is, put it on a scope and observe the > bottom of the ripple) under full load is very relevant to making sure > you have enough headroom for your regulator. > > If you don't have a scope you can guess what the ripple is from > average DC and rectifier type (half or full wave). Guess won't be far > off from reality unless you've got abysmal ESR caps or really really > sucky transformer. > > As to headroom: Typically for a high-current supply on a 723 chip, > there would be a "secondary" supply at higher DC voltage that helped > you develop drive to the pass transistor. Without this you need several > extra volts headroom. > > So far you haven't given us an awful lot to go on :-). > > Tim. > Article: 97393 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: 13.8V high current power supply - update Message-ID: <4p25625k1r15c8beus1v1oo99m24b39rgu@4ax.com> References: <1147103416.176308.205570@y43g2000cwc.googlegroups.com> <1147280376.352051.67700@j73g2000cwa.googlegroups.com> Date: Thu, 11 May 2006 01:04:23 GMT On 10 May 2006 09:59:36 -0700, paul@burridge8333.fsbusiness.co.uk wrote: >Interesting. There are all sorts of protections one can build into PSUs >of course and it's a job to know where to stop with some of them. I'm >just wondering why there's a need to limit this inrush current. What is >it you're seeking to protect here? For protection you need primary (line side) fusing and most put some kind of fusing on the secodary side as well. Then over current protection. Limiting inrush current is mostly to protect the diodes as the first charge the caps. For the first few ac cycles those caps look like a dead short or mightly close. Under those conditions the diodes have to stand the short circuit current the transformer can provide which can easily exceed diode rating if care is not taken. Soft start (inrush protection) can be as simple as a series resistance on the primary with a realy to short it out after a few seconds. Having worked on 13.8V 80A power supplies in the past I can say while the voltages are relatively low the stored energy (and resulting currents) can be massive. This high energy demands respect. I've seen screwdrivers with 1/4" shanks dropped in 50A supplies start an arc that resulted in the screwdrivers destruction. Ring ans otehr jewlery are also fair game and if they melt with the owner attached it's going to be painful. Fuse it well with rated fuses and also provide a bleed load to discharge the caps when powered down. Allison Article: 97394 of rec.radio.amateur.homebrew From: Paul Keinanen Subject: Re: 13.8V high current power supply - update Message-ID: <4rt562pa8vn5frfk7t8medr0nr3dhhvuqn@4ax.com> References: <1147103416.176308.205570@y43g2000cwc.googlegroups.com> <1147280376.352051.67700@j73g2000cwa.googlegroups.com> <4p25625k1r15c8beus1v1oo99m24b39rgu@4ax.com> Date: Thu, 11 May 2006 11:35:57 +0300 On Thu, 11 May 2006 01:04:23 GMT, Allisonnospam@nouce.bellatlantic.net wrote: >Limiting inrush current is mostly to protect the diodes as the first >charge the caps. For the first few ac cycles those caps look like a >dead short or mightly close. Under those conditions the diodes have >to stand the short circuit current the transformer can provide which >can easily exceed diode rating if care is not taken. Also if a toroid mains transformer is used, the transformer start-up current can be huge for a large (say 1 kVA) transformer, which could harm the house wiring or burn the fuses in the main distribution panel. Depending at what mains cycle phase angle the transformer was previously disconnected and on what phase angle it is reconnected to the mains, the start-up peak can be insignificant or the current can be huge, which is limited just by the copper resistance of the primary. Paul OH3LWR Article: 97395 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: 13.8V high current power supply - update Message-ID: References: <1147103416.176308.205570@y43g2000cwc.googlegroups.com> <1147280376.352051.67700@j73g2000cwa.googlegroups.com> <4p25625k1r15c8beus1v1oo99m24b39rgu@4ax.com> <4rt562pa8vn5frfk7t8medr0nr3dhhvuqn@4ax.com> Date: Thu, 11 May 2006 11:59:44 GMT On Thu, 11 May 2006 11:35:57 +0300, Paul Keinanen wrote: >On Thu, 11 May 2006 01:04:23 GMT, Allisonnospam@nouce.bellatlantic.net >wrote: > >>Limiting inrush current is mostly to protect the diodes as the first >>charge the caps. For the first few ac cycles those caps look like a >>dead short or mightly close. Under those conditions the diodes have >>to stand the short circuit current the transformer can provide which >>can easily exceed diode rating if care is not taken. > >Also if a toroid mains transformer is used, the transformer start-up >current can be huge for a large (say 1 kVA) transformer, which could >harm the house wiring or burn the fuses in the main distribution >panel. > >Depending at what mains cycle phase angle the transformer was >previously disconnected and on what phase angle it is reconnected to >the mains, the start-up peak can be insignificant or the current can >be huge, which is limited just by the copper resistance of the >primary. > >Paul OH3LWR Well thats true but those familiar with transformer action would note that is the secondary sees a short the primary will also draw current limited by magnetic coupling/saturation and DC resistance hence which is how you can get massive primary currents. this is not limited to when toroid mains transformers are used as any well designed transformer capable of full load will behave the same. As far as harming house fuses or wiring, here in the USA and I'd bet most elsewhere the electrical codes provide for time delay fuses for surge loads and house wiring that is sufficently robust to withstand the rated current of the distribution fuses. That should not be an issue and the power supply should have it's own fusing. It could be a nusance if the power supply has a massive enough surge to open the mains fuse but there is not safety issue unless the mains fuse or wiring is improppper. However for big power supplies be they HV or LV startup current does require attention if only to assure turning it on will put you in the dark. ;) Allison Article: 97396 of rec.radio.amateur.homebrew From: Roy Lewallen Subject: Re: 13.8V high current power supply - update Date: Thu, 11 May 2006 11:18:56 -0700 Message-ID: <126701f6kpcp691@corp.supernews.com> References: <1147103416.176308.205570@y43g2000cwc.googlegroups.com> <1147280376.352051.67700@j73g2000cwa.googlegroups.com> <4p25625k1r15c8beus1v1oo99m24b39rgu@4ax.com> <4rt562pa8vn5frfk7t8medr0nr3dhhvuqn@4ax.com> Paul Keinanen wrote: > > Also if a toroid mains transformer is used, the transformer start-up > current can be huge for a large (say 1 kVA) transformer, which could > harm the house wiring or burn the fuses in the main distribution > panel. > > Depending at what mains cycle phase angle the transformer was > previously disconnected and on what phase angle it is reconnected to > the mains, the start-up peak can be insignificant or the current can > be huge, which is limited just by the copper resistance of the > primary. This might be a good time to mention that light bulbs, which I've seen recommended here as a test load, have a resistance when cold that's only about a tenth their resistance when hot. So you'll get some pretty awesome current when you first connect one. A supply with foldback current limiting probably won't light one at all unless the voltage is raised slowly. Roy Lewallen, W7EL Article: 97397 of rec.radio.amateur.homebrew From: "Mike Andrews" Subject: Re: 13.8V high current power supply - update Date: Thu, 11 May 2006 18:52:40 +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> Roy Lewallen wrote: > This might be a good time to mention that light bulbs, which I've seen > recommended here as a test load, have a resistance when cold that's only > about a tenth their resistance when hot. So you'll get some pretty > awesome current when you first connect one. A supply with foldback > current limiting probably won't light one at all unless the voltage is > raised slowly. That's a cool thing to know. 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: 97398 of rec.radio.amateur.homebrew From: dplatt@radagast.org (Dave Platt) Subject: Re: TCXO Substitution? Date: Thu, 11 May 2006 19:57:27 -0000 Message-ID: <12675p7pbagk02d@corp.supernews.com> References: <1147373350.498396.182210@i39g2000cwa.googlegroups.com> In article <1147373350.498396.182210@i39g2000cwa.googlegroups.com>, wrote: >I have been searching for a Kenwood SO-1 temperature compensated >crystal oscillator for the last 4 years. When I did find them (eBay), >they went for a fortune because I must not be the only looking for one. > I believe the SO-1 runs at 20Mhz...are there other units that could be >substituted? I believe the Kenwood SO-2, with also runs at 20Mhz, is >still available. Can the SO-2 be wired in place of the SO-1? Or is >there more to it than that? Perhaps check out http://www.icmfg.com/tcxofaqs.html and see if they make a TXCO which is suitable, or can be adapted to work with the supply voltages and output-signal requirements of whatever piece of (Kenwood?) equipment you plan to use this with? They say that their TXCOs are available at frequencies of up to 20 MHz, as standard items, and that higher frequencies may be available. There are probably other manufacturers of TXCOs that you could adapt. -- 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: 97399 of rec.radio.amateur.homebrew From: Straydog Subject: Re: 13.8V high current power supply - update Date: Thu, 11 May 2006 19:24:58 -0400 Message-ID: References: <1147103416.176308.205570@y43g2000cwc.googlegroups.com> On Thu, 11 May 2006, Mike Andrews wrote: > Roy Lewallen wrote: > >> This might be a good time to mention that light bulbs, which I've seen >> recommended here as a test load, have a resistance when cold that's only >> about a tenth their resistance when hot. So you'll get some pretty >> awesome current when you first connect one. A supply with foldback >> current limiting probably won't light one at all unless the voltage is >> raised slowly. > > That's a cool thing to know. FYI, vacuum tube filaments show the same thing. Lower ohms when cold. More below... > 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_. 35 KV at 700 ma? Exploding wires might not dump all the charge (what size capacitor?). Maybe need 2-3 dozen carbon resistors in series with a milliamp meter to monitor remaining voltage? > -- > Mike Andrews, W5EGO > mikea@mikea.ath.cx > Tired old sysadmin > Article: 97400 of rec.radio.amateur.homebrew From: Roberto IZ5FCY Subject: Want Yaesu schematic Date: Fri, 12 May 2006 09:00:01 +0200 Message-ID: <1ruoygoftx29z.147wtdg4twq27$.dlg@40tude.net> Hi to everyone, I'm looking for the Yaesu FTV-1000 6m Transverter schematic. Can you send me a copy? Many thanks in advance. -- 73's de IZ5FCY Roberto Article: 97401 of rec.radio.amateur.homebrew From: Roy Lewallen Subject: Re: VFO output power Date: Fri, 12 May 2006 01:44:31 -0700 Message-ID: <1268ioekr9pcl8b@corp.supernews.com> References: <1147241561.722283.227940@g10g2000cwb.googlegroups.com> <1147275863.902102.8480@j73g2000cwa.googlegroups.com> <1147415104.249154.15630@j33g2000cwa.googlegroups.com> aadu.adok@gmail.com wrote: > ok, > > I replaced my buffer stages with a single class-A stage (used the same > 2N3904). I even used the same broadband transformer. Good looking 4v > p-p sine appeared on secondary winding. After adding 6db attenuator I > finally got my 1.5 volts p-p going towards diode-ring mixer.. > > thanks guys! I usually try to make my buffer output impedance 50 ohms (which you should have from the attenuator assuming it's a 50 ohm attenuator), and about 2.5 volts p-p open circuit (when not connected to the mixer). This makes sure the mixer diodes get turned on good and hard. When connected to the mixer, you should see a squarish waveform, not just a slightly flattened sine wave. Roy Lewallen, W7EL Article: 97402 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: VFO output power Message-ID: References: <1147241561.722283.227940@g10g2000cwb.googlegroups.com> <1147275863.902102.8480@j73g2000cwa.googlegroups.com> <1147415104.249154.15630@j33g2000cwa.googlegroups.com> <1147422994.686895.74930@j73g2000cwa.googlegroups.com> <1147434688.161592.212690@g10g2000cwb.googlegroups.com> <1147441379.706346.53680@d71g2000cwd.googlegroups.com> <1147442503.583641.252230@u72g2000cwu.googlegroups.com> Date: Fri, 12 May 2006 17:52:17 GMT On 12 May 2006 07:01:43 -0700, "Tim Shoppa" wrote: >Leon wrote: >> > It looks like a degenerated darlington pair (with some "pull-down" to >> > help clear out base charge) to me. Lots of isolation between in and out >> > I'm sure, but really class C into a broadband transformer which means >> > you'll get lots of harmonics out. >> >> It's an ordinary DC-coupled pair circuit, there shouldn't be any >> distortion. I've used something similar as a microphone amplifier. > >It may have been the intention for there to be little distortion but >the waveforms really make it look like it was being driven into cutoff >(the flat-topping at point 2). > >Even though it was being driven into cutoff the amplitudes are still >small so something is out of whack with biasing. Maybe there was >supposed to be a blocking capacitor in series with the 10K on Q2's >base. > >Tim. Tim best bet is the output is insufficiently loaded (at the collector) and the amp is being driven to starvation. I use that circuit but with far different values with excellent results. Allison Article: 97403 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: VFO output power Message-ID: References: <1147241561.722283.227940@g10g2000cwb.googlegroups.com> <1147275863.902102.8480@j73g2000cwa.googlegroups.com> <1147415104.249154.15630@j33g2000cwa.googlegroups.com> <1268ioekr9pcl8b@corp.supernews.com> <1147431611.429264.160840@i39g2000cwa.googlegroups.com> <1147441165.102031.34280@d71g2000cwd.googlegroups.com> Date: Fri, 12 May 2006 18:11:05 GMT On 12 May 2006 06:39:25 -0700, "Tim Shoppa" wrote: >aadu.adok@gmail.com wrote: >> Should I add a low pass chebyshev filter between VFO and mixer? >> I mean - does it give real benefit (or only in theory)? > >If the harmonics are coming in such that they make the LO injection >look asymmetrical, then they could be bad and should be eliminated. > >Harmonics that are fairly symmetrical (e.g. odd multiples of the >fundamental) are not so bad. > >Front end selectivity ahead of the mixer will matter some. > >Any parasitic oscillations (e..g. things that look like spikes at >certain points in the waveform possibly due to resonances/"ringing" in >active or passive devices or parasitics) are very bad and can cause >broadband noise that even your chebyshev low-pass will have a hard time >removing. Making sure that all the buffers are firmly biased in class A >will help make sure you don't have any parasitics to begin with. If >you've got parasitics in your LO chain then no amount of filtering will >help! > >Tim. I'd not put the 1k resistor from emitter of the first transistor to ground in circuit. The turns ratio of the transformer has the collector running around 400ohms (assuming FT37-43 ferrite) which is a bit high for decent power out before compression (clipping). For a +7 to 10dbm output I'd shoot for a 200-250 ohm load. The bias point is non optimum, nearly class C whenit sould be class A with the total collector current in the 8-15ma range. See next. The 10k input resistor does two things. One by it's return to ground via L1 (osc) it sets the bias point and it also serves to set the input resistance of the amp as the 27k negative feedback means the input resistance of the first bipolar is very low. It is a feedback amp. The bias point is not hard to set. Ground the L1 end of the 10K and adjust the feedback resistor (27K ) for 10ma on the collector of The second transistor. Also remove 4turns (16:4 turns) from the primary of the transformer. Try it then and see if things clean up, they usually do. It may be iteritive if the 10K is too low the amp will overdrive and end up looking poor. If the 10k is increased then the feedback resistor will also have to increase to maintain the DC bias point. A low pass filter between the amp and the DBM will insure there are no odd order (3,5,7) harmonics to upset the balance of the DBM. Even order are mostly self cancling due to DBMs balanced design. Allison Article: 97404 of rec.radio.amateur.homebrew From: "Jeff James, W2NBC" Subject: Buy and Sell Tube Gear! Message-ID: Date: Fri, 12 May 2006 14:42:30 -0400 The Boatanchor Classifieds http://www.dealamerica.com/deal/cgi-bin/ads/bcads.cgi Dedicated to Vintage Amateur Radio.. Article: 97405 of rec.radio.amateur.homebrew From: Subject: FA KEITHLEY 610C ELECTROMETER, PICO AMMETER COULOMB METER Plus Message-ID: <8659g.23076$mX1.20976@newsfe2-gui.ntli.net> Date: Fri, 12 May 2006 19:12:04 GMT FA KEITHLEY 610C ELECTROMETER, PICO AMMETER COULOMB METER Plus The shipping with online verification is expensive from the uk .N But this equipmenst may be worth it if you bid right !! http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&rd=1&item=7618143523 emial me on glenron@ntlworld.com Article: 97406 of rec.radio.amateur.homebrew From: Allisonnospam@nouce.bellatlantic.net Subject: Re: VFO output power Message-ID: References: <1147241561.722283.227940@g10g2000cwb.googlegroups.com> <1147275863.902102.8480@j73g2000cwa.googlegroups.com> <1147415104.249154.15630@j33g2000cwa.googlegroups.com> <1268ioekr9pcl8b@corp.supernews.com> <1147431611.429264.160840@i39g2000cwa.googlegroups.com> <1147441165.102031.34280@d71g2000cwd.googlegroups.com> <1147459517.215074.271460@g10g2000cwb.googlegroups.com> Date: Fri, 12 May 2006 21:04:03 GMT On 12 May 2006 11:45:17 -0700, "Tim Shoppa" wrote: > >Allisonnospam@nouce.bellatlantic.net wrote: >> The bias point is non optimum, nearly class C whenit sould be class A >> with the total collector current in the 8-15ma range. > >I agree that the circuit as built exhibited class C behavior in the >buffer. My guesstimate is like 40% of the cycle has conduction. > >But the same identical circuit has been floating around for at least a >decade and has supposedly been built into many many different varities >of rigs with great success. > >I'm wondering if one or more of the following is true: > >1) For most applications it doesn't matter that the buffer is running >class C >2) If the circuit's bias is insensitive to normal variations in real >transistors >3) If "bad luck" out-of-nominal-tolerance transistors contribute to the >particular example built and scoped out. > >Leon said he simulated it (SPICE?) and it worked OK there but a single >simulation using nominal transistor parameters is hardly enough to >guarantee real-world bias being stable. > >My reaction to finding the buffer only in conduction for less than half >a cycle would've been similar to yours, Allison, with maybe more brute >force and a little less finesse in trying different resistor values >:-). > >Tim. It's a classic circuit and like many DC coupled designs it's possible to make it not work right. It's appeared in QST, EMRFD, and even the RAH. It should be biased (with no osc input) as class A. But even the if over driven it would look clipped on the negative going side due to lack of current. Every time I've used that circuit I never had the 1K >from base to ground and the 10K was really more like 22k and the 27K was more like 47-56k when using 3904s. Done right 13Dbm is easy. The alternate is a pair of 2N3904s in a common emitter with DC couped emitter follower using feedback. More than enough gain and output to drive a DBM. Allison Article: 97407 of rec.radio.amateur.homebrew From: Roger Subject: Re: FA KEITHLEY 610C ELECTROMETER, PICO AMMETER COULOMB METER Plus Message-ID: References: <8659g.23076$mX1.20976@newsfe2-gui.ntli.net> Date: Fri, 12 May 2006 19:48:40 -0400 On Fri, 12 May 2006 19:12:04 GMT, wrote: >FA KEITHLEY 610C ELECTROMETER, PICO AMMETER COULOMB METER Plus > >The shipping with online verification is expensive from the uk .N But this >equipmenst may be worth it if you bid right !! > >http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&rd=1&item=7618143523 At one time I had several rack mount Kiethley's in the 600 series but their imput impedance was extremely high. I don't remember the numbers now but they were far higher than normal VTVMs. We workd with resistances where a fingerprint on the tubes (they used pencil tubes) could mess up the readings. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com > >emial me on glenron@ntlworld.com >