Date: Sat, 26 Feb 94 04:30:30 PST From: Ham-Homebrew Mailing List and Newsgroup Errors-To: Ham-Homebrew-Errors@UCSD.Edu Reply-To: Ham-Homebrew@UCSD.Edu Precedence: Bulk Subject: Ham-Homebrew Digest V94 #43 To: Ham-Homebrew Ham-Homebrew Digest Sat, 26 Feb 94 Volume 94 : Issue 43 Today's Topics: Challenge: Cheapest (least expensive) homebrew 2m voice rig Ham-Homebrew Digest V94 #42 How about VHF MOSFET's for 2-meter amp? How to measure low power @ VHF & above. (2 msgs) Paralleling Power Diodes ? S-Band converter design Where is Dan's Small Parts? where to get xtal sockets? Send Replies or notes for publication to: Send subscription requests to: Problems you can't solve otherwise to brian@ucsd.edu. Archives of past issues of the Ham-Homebrew Digest are available (by FTP only) from UCSD.Edu in directory "mailarchives/ham-homebrew". We trust that readers are intelligent enough to realize that all text herein consists of personal comments and does not represent the official policies or positions of any party. Your mileage may vary. So there. ---------------------------------------------------------------------- Date: Fri, 25 Feb 1994 16:35:17 GMT From: mvb.saic.com!unogate!news.service.uci.edu!usc!howland.reston.ans.net!paladin.american.edu!constellation!osuunx.ucc.okstate.edu!olesun!gcouger@network.ucsd.edu Subject: Challenge: Cheapest (least expensive) homebrew 2m voice rig To: ham-homebrew@ucsd.edu For a low cost fm reciver a Signetics 604 looks very good over the same range uisng 4 resistors, 8 capacitors, 1 tank curcuit and a ceramic IF filter and has audio and data outputs. It would also need a couple of stages of audio gain. As I recall the chip is also in the $5.00 range. Gordon AB5Dg Gordon Couger Biosystems & Agricultural Engineering Oklahoma State University 114 Ag Hall, Stillwater, OK 74074 gcouger@olesun.agen.okstate.edu 405-744-9763 day 624-2855 evenings I do not speak for my employer ------------------------------ Date: 25 Feb 94 13:46:04 GMT From: news-mail-gateway@ucsd.edu Subject: Ham-Homebrew Digest V94 #42 To: ham-homebrew@ucsd.edu You can probably buy the crystal sockets from Petersen Radio. I've gotten HC-6 sockets from them in the past. They advertise in the back of QST and have responded very quickly to every order I've placed with them. 712-323-7539. ------------------------------ Date: 24 Feb 94 18:09:36 GMT From: auratek!epacyna@uunet.uu.net Subject: How about VHF MOSFET's for 2-meter amp? To: ham-homebrew@ucsd.edu In article <1994Feb22.215224.22050@ultb.isc.rit.edu>, jdc3538@ultb.isc.rit.edu (J.D. Cronin) writes: > > What are the advantages/disadvantages of RF power MOSFET's? From what > the listing shows, they have more gain than bipolars. Are there any > "gotchyas"? How does efficiency compare? They are listed for 28 or > 50 volt supplies. How much power can you get at 12 volts? The 1994 > ARRL handbook doesn't seem to cover any of this. > ------------------------------ Date: 24 Feb 94 12:53:59 CST From: elroy.jpl.nasa.gov!swrinde!gatech!howland.reston.ans.net!vixen.cso.uiuc.edu!uchinews!cdsmail!timbuk.cray.com!hemlock.cray.com!andyw@ames.arpa Subject: How to measure low power @ VHF & above. To: ham-homebrew@ucsd.edu In article , glenne@sad.hp.com (Glenn Elmore) writes: > The lowball method I use is a calibrated Schottkey diode detector. > [two good references deleted..] > of wheat size) lamps and seems to get reasonable performance to 500 MHz. Thanks a lot, I'll track down the references - anyone else interested in the articles (email me, if there's tons of you I'll post the results). I also got an email (thanks Julian !) suggesting the RF voltmeter across a load (I was wondering how to calibrate it, sounds like the article Glenn mentioned will tell me.) -- andyw N0REN/G1XRL andyw@aspen.cray.com Andy Warner, Cray Research, Inc. (612) 683-5835 ------------------------------ Date: Thu, 24 Feb 1994 17:36:20 GMT From: unogate!news.service.uci.edu!usc!elroy.jpl.nasa.gov!swrinde!cs.utexas.edu!convex!news.utdallas.edu!wupost!udel!news.intercon.com!panix!ddsw1!news.kei.com!ub!newserve!sarah!@mvb.saic.com Subject: How to measure low power @ VHF & above. To: ham-homebrew@ucsd.edu Andy Warner (andyw@aspen32.cray.com) wrote: : Anyone have any favourite methods for measuring VHF/UHF : power in the 1 - 10 mW range ? I can't just go out and : buy a bolometer, so what do people suggest ? Recent editions of the ARRL Handbook have John Grebenkemper's Tandem Match (also Jan 1987 QST). The diode detector circuit will work just fine at VHF, though it probably degrades at bit at UHF. My guess is that it will be still usable at 450 MHz. This circuit uses an OP amp and another diode to compensate for the nonlinearity of the detector. : FWIW, I have two immediate applications, one is connecting : a transverter to a TS-711A, the other is measuring the output : power of a small UHF oscillator & amplifier. -- Zack Lau KH6CP/1 2 way QRP WAS 8 States on 10 GHz Internet: zlau@arrl.org 10 grids on 2304 MHz ------------------------------ Date: Thu, 24 Feb 94 23:12:13 GMT From: sequent!muncher.sequent.com!edw@uunet.uu.net Subject: Paralleling Power Diodes ? To: ham-homebrew@ucsd.edu You answered your own question. Paralleling diodes with diff forward resistance is a problem. -- I think I've got the hang of it now .... :w :q :wq :wq! ^d X exit ^X^C ~. ^[x X Q :quitbye CtrlAltDel ~~q :~q logout save/quit :!QUIT ^[zz ^[ZZ ZZZZ ^H ^@ ^L ^[c $q ^# ^E ^X ^I ^T ? help helpquit ^D ^d ^C ^c help ^]q exit ?Quit ?q anybackbone!sequent!edw edw@sequent.COM KA9AHQ 28.340 ------------------------------ Date: 25 Feb 1994 18:12:22 GMT From: unogate!news.service.uci.edu!usc!howland.reston.ans.net!europa.eng.gtefsd.com!news.umbc.edu!eff!news.kei.com!yeshua.marcam.com!zip.eecs.umich.edu!umn.edu!dawn.mmm.com!@@mvb.saic.com Subject: S-Band converter design To: ham-homebrew@ucsd.edu Does anyone have a proven design for an S-Band (1691-1708 MHz) to 2 meter (144-148 MHz) converter? No mater where you go, there you are! Cheers & 73 KA0TUT ------------------------------ Date: Thu, 24 Feb 1994 22:39:23 GMT From: math.ohio-state.edu!howland.reston.ans.net!vixen.cso.uiuc.edu!sdd.hp.com!saimiri.primate.wisc.edu!nntp.msstate.edu!olivea!sgigate.sgi.com!odin!chuck.dallas.sgi.com!@@news.acns.nwu.edu Subject: Where is Dan's Small Parts? To: ham-homebrew@ucsd.edu The current address that is correct is the one in Montana. Missoula is the name of the town. Latest issues of QST (back section), 73, and CQ all have listings in the small ads (personals) in the back. dit dit -- Chuck Adams K5FO CP-60 adams@sgi.com ------------------------------ Date: Thu, 24 Feb 1994 17:42:07 GMT From: mvb.saic.com!unogate!news.service.uci.edu!usc!sol.ctr.columbia.edu!news.kei.com!ub!newserve!sarah!rpi!psinntp!psinntp!arrl.org!zlau@network.ucsd.edu Subject: where to get xtal sockets? To: ham-homebrew@ucsd.edu Dave Duchesneau (daved@autodesk.com) wrote: : I'm building a QRP 3-bander from the ARRL Handbook, and have : everything I need except for sockets for the crystals, which I : can't find anywhere! Can anyone point me to a source for PC-mount : HC-49U (the small size crystals) sockets, or sell me four or five? : I'd really appreciate it! I got a bunch from International Crystals. These plastic ones do melt, so be careful when you solder them in. I don't think I've ever seen ceramic crystal sockets in this size. At one time, they were 60 cents each or 10/4.50. -- Zack Lau KH6CP/1 2 way QRP WAS 8 States on 10 GHz Internet: zlau@arrl.org 10 grids on 2304 MHz ------------------------------ Date: Thu, 24 Feb 1994 16:55:08 GMT From: mvb.saic.com!unogate!news.service.uci.edu!usc!sol.ctr.columbia.edu!news.kei.com!ub!newserve!sarah!rpi!psinntp!psinntp!arrl.org!zlau@network.ucsd.edu To: ham-homebrew@ucsd.edu References <2jogqu$7lb@usenet.INS.CWRU.Edu>, <3412@grivel.une.edu.au>, serve Subject : Re: Good substitute for 1N23 as noise source? There is a company called Noise/Com E. 49 Midland Avenue, Paramus NJ 07652 201-261-8797 FAX 201 261-8339 that sells noise diodes from .1 Hz to 110 GHz. I'd guess that the millimetric ones are expensive enough that small quantity orders are routine. Tommy Henderson wrote up an article using the NC303 diode and found it to produce a 4.6 +/- .2 dB ENR from 150 MHz to 2300 MHz. It appeared in on page 59 of the 1993 Central States Proceedings (27th conference). -- Zack Lau KH6CP/1 2 way QRP WAS 8 States on 10 GHz Internet: zlau@arrl.org 10 grids on 2304 MHz ------------------------------ Date: (null) From: (null) Easy to bias with simple circuitry (vs bi-polar) since the gate comsumes no real power. You can also easily use the bias to control the stage gain. There is also much more flexibility to define the stage input Z for easy matching. Most RF Power MOSFets are spec'd at higher supply voltage (Vd), typically have higher Vsat, but will run at reduced efficiency with 12 volt supplys. Also, you can save money by using a power MOSFet designed for switching (e.g. IRF511, IRF530 etc.) in the HF region. 73 Ed W1AAZ ------------------------------ Date: Thu, 24 Feb 1994 17:28:24 GMT From: mvb.saic.com!unogate!news.service.uci.edu!usc!math.ohio-state.edu!magnus.acs.ohio-state.edu!usenet.ins.cwru.edu!eff!news.kei.com!ub!newserve!sarah!rpi!psinntp!psinntp!arrl.org!zlau@@.. To: ham-homebrew@ucsd.edu References <2jogqu$7lb@usenet.INS.CWRU.Edu>, <1994Feb15.165930.23950@ke4zv.atl.ga.us>, <2k0oso$qg3@ornews.intel.com>e.edu Subject : Re: gasFETs for preamps Jim Garver (zardoz@ornews.intel.com) wrote: : I finally toasted the gasFET in my old Hamtronics 2 meter preamp somehow. : I called Hamtronics and they said that they are an appliance outlet only now. : What is a good, cheap source for these devices? Mine was supposed to have : been .7 db noise with 13-20 db gain, that's all I know. If it is a dual gate GaAs FET, you might try something like the NE41137. If it is a single gate FET, then a MGF 1302 is probably OK. At 2 meters, there isn't too much difference, though you don't want to use a Ku band (12 GHz) FET because the 1/f noise will result in poor performance. While there are a few designs that are critical, such as the recent DJ9BV one in Dubus optimized for stability as well as noise figure, many 2M designs are probably designed by trial and error, rather around the characteristics of a specific FET. : Other than soldering them in, what are the hazards once installed? How : much loosely capacitively coupled energy can the gate take? What is the : detrimental effect of installing the preamp inside a rig after a chain of : PIN diodes and other junK? (other than a hacked up rig, of course). : I don't want to mast mount it and I use 75 ohm 3/4" hardline. : Thanks, Depends on the rig. I seem to remember the IC-402 70 cm rig having a 1.5 dB loss BPF between the relay and antenna jack. Thus, a .3 dB NF preamp would give you a 1.8 dB NF at best if connected between the relay and receiver. PIN diodes can have losses as low as 0.3 dB, theoretically, but 1 to 2 dB is probably more typical. One way of reducing the losses is to use high power PIN diodes and running lots of current though them (100 mA). Sometimes, you can get the current by running it through the diode and then some other circuitry (when you want to keep current consumption low). The preamp is more susceptible to damage with the preamp off, though it could produce a big signal that damages your receiver. 10 dBm seems to be a safe level, though I've heard that PHEMTs used at microwaves *are* more easily damaged. I'd guess that it is tough to improve many modern rigs with just a better preamp after the T/R circuitry. The existing preamp probably has a 1 or 2 dB NF, but all that junk (especially the thin coax cables) raise it by a couple more dB. Probably makes sense, since even 50 ft of RG-8 coax adds another dB to the noise figure at 2 meters. 100 ft of that 3/4 inch hardline adds about .8 dB to your noise figure. It should be kept in mind that preamps usually result in more intermod problems--to get a 1 dB system noise figure may require so much preamp gain that the mixer overloads in some metropolitan areas on 2 meters. Thus, a preamp may degrade performance. -- Zack Lau KH6CP/1 2 way QRP WAS 8 States on 10 GHz Internet: zlau@arrl.org 10 grids on 2304 MHz ------------------------------ Date: Fri, 25 Feb 1994 05:51:09 GMT From: mvb.saic.com!unogate!news.service.uci.edu!usc!elroy.jpl.nasa.gov!swrinde!gatech!europa.eng.gtefsd.com!news.uoregon.edu!cs.uoregon.edu!efn!matt@network.ucsd.edu To: ham-homebrew@ucsd.edu References , <1994Feb20.161304.17180@ke4zv.atl.ga.us>, <21FEB199409414816@pavo.concordia.ca>egon.edu Subject : Re: What test equipment do you use? In <21FEB199409414816@pavo.concordia.ca> md_hill@pavo.concordia.ca (HILLIER, MARK D.) writes: >Great idea. Anyone who wishes that they had such a piece of equipment can build >one for next to nothing. The ARRL handbook page 27-31 (year 199?) has a great >little circuit that works very well. One drawback is that for it too be useful >for the lengths of coax that amateurs usually use (i.e. around 50ft) then you >NEED a scope with a bandwidth of 50MHz or more. >Enjoy There is also an article in May 89 QST p. 22 called "A Practical Time-Domain Reflectometer" matt@efn.org n0gth ------------------------------ End of Ham-Homebrew Digest V94 #43 ****************************** ******************************