Date: Fri, 13 May 94 04:30:19 PDT 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 #127 To: Ham-Homebrew Ham-Homebrew Digest Fri, 13 May 94 Volume 94 : Issue 127 Today's Topics: UHF Power amps. UHF Push/Pull design ? Xtal temp. compensation? (2 msgs) 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: Thu, 12 May 1994 09:45:01 -0500 From: ihnp4.ucsd.edu!newshub.sdsu.edu!nic-nac.CSU.net!usc!howland.reston.ans.net!EU.net!sunic!psinntp!psinntp!pbs.org!jernandez.pbs.org!user@network.ucsd.edu Subject: UHF Power amps. To: ham-homebrew@ucsd.edu In article , jfk@cs.adel.edu.au (John Kavanagh) wrote: > Hi, > > Does anyone know of any good articles or books with practical circuits for the > construction of power amps for 70cm. Look in the Motorola RF device catalog. It has a multitude of good app notes in the back of the book. -- John J. Ernandez Communication Systems Engineer Public Broadcasting Service E-Mail jernandez@pbs.org Member:PRR Technical & Historical Society Phone: 703-739-5474 Southern Railway Historical Association Amateur Radio: KA2YAP ------------------------------ Date: Wed, 11 May 1994 04:27:40 GMT From: ihnp4.ucsd.edu!usc!cs.utexas.edu!swrinde!emory!kd4nc!ke4zv!gary@network.ucsd.edu Subject: UHF Push/Pull design ? To: ham-homebrew@ucsd.edu In article <2qnl9m$4vo@cismsun.univ-lyon1.fr> elendir@enst.fr (Elendir) writes: > > I have been scared by the price of the latest VHF/UHF all mods rigs. So >I decided to build my own. However, I©m looking for a UHF Push-Pull design. >The very problem I have is in the design of the 180 degrees phase shifter. >In VHF, I can use a small transformer with a ground tap in the middle, but >this cannot be applied to UHF. I thought about a printed transformer or a >transistor operating as an inverter. Neither those seem really satisfactory. >Does someone have any clue ? Sure just use a halfwave of transmission line as a very simple balun. It works for antennas, and it'll work as a push-pull input network too. Gary -- Gary Coffman KE4ZV | You make it, | gatech!wa4mei!ke4zv!gary Destructive Testing Systems | we break it. | uunet!rsiatl!ke4zv!gary 534 Shannon Way | Guaranteed! | emory!kd4nc!ke4zv!gary Lawrenceville, GA 30244 | | ------------------------------ Date: Thu, 12 May 1994 15:34:26 GMT From: pa.dec.com!nntpd2.cxo.dec.com!nntpd.lkg.dec.com!ryn.mro.dec.com!est.enet.dec.com!randolph@decwrl.dec.com Subject: Xtal temp. compensation? To: ham-homebrew@ucsd.edu I'm building a simple crystal freq reference... something I can zero beat against WWV, and then use as a standard for setting my freq. counter. Any thoughts on temperature compensation for this? I have an old Motorola HT220 (soon to be moved down to the 440 ham band) in which they use a cap and thermistor, like this: !+-+! ---o------!! !!----------o---- ! !+-+! ! ! ! ! !! ! +---!!--------/\/\/---+ !! Sure beats a crystal oven, if I can figure out a way to implement it. What do I need to think about in designing this little circuit? -Tom R. N1OOQ randolph@est.enet.dec.com ------------------------------ Date: Thu, 12 May 1994 19:43:23 GMT From: ihnp4.ucsd.edu!news.cerf.net!mvb.saic.com!MathWorks.Com!europa.eng.gtefsd.com!howland.reston.ans.net!math.ohio-state.edu!magnus.acs.ohio-state.edu!csn!col.hp.com!srgenprp!alanb@network. Subject: Xtal temp. compensation? To: ham-homebrew@ucsd.edu Tom Randolph (randolph@est.enet.dec.com) wrote: : I'm building a simple crystal freq reference... something I can zero beat : against WWV, and then use as a standard for setting my freq. counter. : Any thoughts on temperature compensation for this? ... The problem is that quartz crystals do not have a linear frequency versus temperature curve. Standard AT-cut crystals are generally manufactured so that the inflection point in the F vs t curve is flat at room temperature. So no compensation is needed so long as you stay close to room temperature and the rest of your circuit doesn't degrade crystal stability. Crystals intended for use in temperature-controlled ovens are designed to have a flat inflection point at the oven temperature. Let's see if I can do an ASCII graph of an AT-cut crystal's frequency versus temperature curve: \ ^ \ | \ | \ Freq \ \ - - _ ----------- _ - - \ \ \ \ \ | \ Temperature -----> 25 deg C AL N1AL ------------------------------ End of Ham-Homebrew Digest V94 #127 ******************************