Date: Tue, 21 Jun 94 04:30:35 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 #169 To: Ham-Homebrew Ham-Homebrew Digest Tue, 21 Jun 94 Volume 94 : Issue 169 Today's Topics: Cavities cheap cases wanted (2 msgs) L.O FOR 1.2, 1.3, 1.4, 1.5 GHZ Square transmission lines (3 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: 21 Jun 1994 09:07:18 GMT From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!math.ohio-state.edu!jussieu.fr!univ-lyon1.fr!elendir@network.ucsd.edu Subject: Cavities To: ham-homebrew@ucsd.edu Hello ! Does someone have any interesting pointers towards the theory (and practice) of resonating cavities ? I know some facts (frequency, ...) but I am interesting in knowing how to compute Q (Volume/Surface ?) and the formulae for cylindrical cavities. Thanks ! Vince, F1RCS. PS : This is for a repeater project. ------------------------------ Date: Mon, 20 Jun 1994 13:57:09 GMT From: ihnp4.ucsd.edu!usc!sol.ctr.columbia.edu!news.ess.harris.com!adm01.rfc.comm.harris.com!gdian22@network.ucsd.edu Subject: cheap cases wanted To: ham-homebrew@ucsd.edu Forunately for me, there are a couple surplus electronics parts stores here in the rochester ny area, so cheap project boxes are available. I have used printed circuit board material to make enclosures too. The Doug DeMaw (w1fb) qrp books describe this method. I use my table saw to cut the board to size, then solder the box together. A lot of my projects use plexiglass for a top, so you can see all the goodies inside. Yes, in some cases hand capacitance can play into operation of the radio, so be careful about using a plastic lid. Anyway, I pay 2 cents per square inch of single sided board, so the enclosure price is low. I also have a small aluminum break (sp?) on order from harbor freight (left coast import tool company), so I can get sheet aluminum and form cases that way (i.e. nice 90 degree angles, smooth bends). 73, gary n2jgu ------------------------------ Date: 20 Jun 1994 23:07:03 -0400 From: newstf01.cr1.aol.com!search01.news.aol.com!not-for-mail@uunet.uu.net Subject: cheap cases wanted To: ham-homebrew@ucsd.edu In article <2u5i3j$a1h@crl.crl.com>, frbspd@crl.com (Stephen Dunifer) writes: *all that good stuff...* I've found with the pc board cases that really thick pc board works better, especially for places where there are plug-ins (power leads, antennas, etc). Fortunately there is a relatively cheap source of the thick stuff locally-->1/8th inch thick, 5 square feet for $5. I once found an extruded aluminum 3X5 card file box (mil surplus, of course) that is about 1/8th inch thick and a *fantastic* radio box!!! Good luck!! 72 (+/- 1) Jim N0OCT ------------------------------ Date: 20 Jun 1994 21:54:19 GMT From: ihnp4.ucsd.edu!sdd.hp.com!hpscit.sc.hp.com!rkarlqu@network.ucsd.edu Subject: L.O FOR 1.2, 1.3, 1.4, 1.5 GHZ To: ham-homebrew@ucsd.edu In article , Mike Lyon wrote: >well i am trying to design a L.O for 1.2, 1.3, 1.4, 1.5 ghz. i don't >think i can do it with crystals (but if anyone thinks i can i would love >to hear from you on how i could do it :). so my idea was to build the >oscilator with the good old caps and inductors (feedback type). the thing >is though is the fact that i can't find any formulas and schematics on >how to build one. i have a schematic for a 2 ghz L.O but it doesn't have >any formulas to figure out the components values. so my question is for >you experts is do you guys or gals have any schematics,formulas or >anything of that nature you could either post or e-mail to me? any light >on this subject would be greatly appreciated. > > thanx alot, > mlyon@rahul.net >-- >Mike Lyon Build a 2 GHz. grounded emitter amplifier using a transistor with an Ft of 5 GHz. or so. (MRF951 will work fine) Now connect the cathode of a Toshiba 1SV186 tuning diode (available from Matcom, Palo Alto, CA) to the collector, which should be connected to VCC with an RF choke. The anode of the tuning diode is coupled via a 100 pF. capacitor to the base. This junction also has a 1 K resistor to feed in the tuning voltage, which is relative to VCC. The leads of the diode are the tuning inductance; adjust lead length to get the right frequency range. You should be able to get about an octave. Be sure to use at least 5 DC volts across the emitter bias resistor (which of course is RF bypassed) to assure stable bias across the tuning range. Put a 50 ohm load impedance on the collector and no load on the base. Rick Karlquist N6RK rkarlqu@scd.hp.com ------------------------------ Date: Mon, 20 Jun 94 20:22:48 GMT From: ihnp4.ucsd.edu!library.ucla.edu!europa.eng.gtefsd.com!uhog.mit.edu!news.kei.com!ub!galileo.cc.rochester.edu!news@network.ucsd.edu Subject: Square transmission lines To: ham-homebrew@ucsd.edu Could someone clue me in to the formula for calculating the characteristic impedance of a coaxial transmission line with a square shield, ie the cross section looks like... +-----------------+ | | | | | O | | | | | +-----------------+ That's a round center conductor there (ie brass tubing). Possible uses for such a bird would be 1) a directional coupler made out of scrap PC board and a piece of wire or tubing or 2) a tapered-line matching section if one tapers the width of the shield... -Bill VanRemmen, KA2WFJ billy@urhep.pas.rochester.edu URHEP::billy My opinions. No one else's. Definitely not the U of R's. ============================================================================== "Experience should teach us to be most on our guard to protect liberty when the government's purposes are beneficient . . . the greatest dangers to liberty lurk in insidious encroachment by men of zeal, well meaning but without understanding." Justice Louis Brandeis Olmstead vs. United States, United States Supreme Court, 1928 ============================================================================== ------------------------------ Date: Mon, 20 Jun 1994 21:37:24 GMT From: ihnp4.ucsd.edu!library.ucla.edu!europa.eng.gtefsd.com!howland.reston.ans.net!spool.mu.edu!sdd.hp.com!hp-pcd!hpcvsnz!tomb@network.ucsd.edu Subject: Square transmission lines To: ham-homebrew@ucsd.edu Bill VanRemmen (BILLY@urhep.pas.rochester.edu) wrote: : Could someone clue me in to the formula for calculating the characteristic : impedance of a coaxial transmission line with a square shield, ie the cross ------------------------------ Date: Mon, 20 Jun 94 22:50:15 GMT From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!gatech!newsxfer.itd.umich.edu!zip.eecs.umich.edu!yeshua.marcam.com!news.kei.com!ub!galileo.cc.rochester.edu!news@network.ucsd.edu Subject: Square transmission lines To: ham-homebrew@ucsd.edu In tomb@lsid.hp.com writes: > Bill VanRemmen (BILLY@urhep.pas.rochester.edu) wrote: > : Could someone clue me in to the formula for calculating the characteristic > : impedance of a coaxial transmission line with a square shield, ie the cross > > From "Reference Data for Engineers," seventh edition, Howard Sams, given > that D is the box inside side length and d is the inner conductor diameter, > > Zo approx= [138*log(rho)+6.48-2.34*A-0.48*B-0.12*C]/(epsilon)^0.5 > > where epsilon is the relative dielectric constant, > > rho = D/d > > A = (1+0.405*rho^-4)/(1-0.405*rho^-4) > > B = (1+0.163*rho^-8)/(1-0.163*rho^-8) > > C = (1+0.067*rho^-12)/(1-0.067*rho^-12) > > --------------------------- > Well, you asked for it... > > There are also formuale for a single wire in a trough, and a single wire > centered between two parallel ground planes. Thanks Muchly! 73 -Bill VanRemmen, KA2WFJ billy@urhep.pas.rochester.edu URHEP::billy My opinions. No one else's. Definitely not the U of R's. ============================================================================== "Experience should teach us to be most on our guard to protect liberty when the government's purposes are beneficient . . . the greatest dangers to liberty lurk in insidious encroachment by men of zeal, well meaning but without understanding." Justice Louis Brandeis Olmstead vs. United States, United States Supreme Court, 1928 ============================================================================== ------------------------------ Date: (null) From: (null) Zo approx= [138*log(rho)+6.48-2.34*A-0.48*B-0.12*C]/(epsilon)^0.5 where epsilon is the relative dielectric constant, rho = D/d A = (1+0.405*rho^-4)/(1-0.405*rho^-4) B = (1+0.163*rho^-8)/(1-0.163*rho^-8) C = (1+0.067*rho^-12)/(1-0.067*rho^-12) --------------------------- Well, you asked for it... There are also formuale for a single wire in a trough, and a single wire centered between two parallel ground planes. ------------------------------ Date: 20 Jun 1994 19:08:51 -0700 From: nntp.crl.com!crl.crl.com!not-for-mail@decwrl.dec.com To: ham-homebrew@ucsd.edu References , <1994Jun19.203004.25778@bongo.tele.com>, Subject : Re: cheap cases wanted Several places have a series of aluminum and steel cases available for under $10 plus lots of other goodies. Marlin P Jones $ Assoc. (407) 848-8236 - POB 12685, Lake Park, FL 33403 Stock # Size Price 5804-BX 9.5 x 5.0 x 1.5 $4.00 5805-BX 9.0 x 7.0 x 2.0 $4.40 5806-BX 12.0 x 8.0 x 3.0 $5.00 the above are 18ga steel, cadmium plated Hosfelt Electronics (800) 524-6464 - 2700 Sunset Blvd., Stubenville, OH 43952 14-126 4 x 6 x 2 $3.70 14-127 7 x 7 x 2 $4.35 the above are aluminum Also try Mouser Electronics and Digi-Key Stephen Dunifer ------------------------------ Date: Tue, 21 Jun 1994 00:48:30 GMT From: rit!isc-newsserver!ultb!jdc3538@cs.rochester.edu To: ham-homebrew@ucsd.edu References <2tqkg9$f8l@quartz.ucs.ualberta.ca>, <2trc2m$pk5@crl.crl.com>, fer.it Subject : Re: ATV transmitter plans? In article kors@netcom.com (Richard Kors) writes: >Stephen Dunifer (frbspd@crl.com) wrote: >: Reddy Praveen (reddy@ee.ualberta.ca) wrote: >: : does any one know where i can by an inexpensive atv transmitter or where >: : i can get the plans for one >: : I would like something small and self contained that has a NTSC input >: : and an antenna output >: : thanks > >: Check out the latest issue of Electronics Now (July 1994), full diagrams >: and all. > > >The Rabbit cost $29.95 for a transmitter and receiver at 900 mc . What more could a Ham want? > >The Electronics Now kit is very touchy and a challange to build. Mine works, >but I'd never do it again. > >dick kors >kors@netcom.com >km6ep > A sub-mini camera at the same price. And a 440 mhz version of the rabbit for use with our local ATV repeater. And a bunch of people interested in ATV. From what I've heard, there are very few ATV enthusiasts. 73...Jim N2VNO ------------------------------ End of Ham-Homebrew Digest V94 #169 ******************************