Date: Fri, 25 Mar 94 04:30:29 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 #72 To: Ham-Homebrew Ham-Homebrew Digest Fri, 25 Mar 94 Volume 94 : Issue 72 Today's Topics: 2m linear using a pair of 4CX100A's- Help!!! advice fm (2 msgs) Component Databooks ? Kenwood (TS-850) Computer Interface Info Wanted (2 msgs) Noise figure/transistors QSKing an AMP Simple Tx/Rx? What is third order intercept ? 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: 24 Mar 1994 07:51:32 -0600 From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!howland.reston.ans.net!cs.utexas.edu!not-for-mail@network.ucsd.edu Subject: 2m linear using a pair of 4CX100A's- Help!!! To: ham-homebrew@ucsd.edu A friend and I got a couple of new Eimac 4CX1000A's cheaply, and deceided to design a linear amp for 2m around them. For those who don't know the 4CX1000'A, it's a 1000W, class AB1 only tetrode, designed for use to 110MHz, but many designs exist for use at 144MHz. Max current is 1A, max voltage is 3kV. The amlifier is *supposed* to be is push-pull, but I'm not sure that they are, since the amplifier works rather poorly. Any suggestions would be appreciated. It was believed to be *almost finished* about two years ago, but has never worked properly. Because of the cost of the bases, I fabricated a couple from brass and PTFE. To avoid having to make screen decoupling capacitors, the amplifier runs in gronded screen, similar to the design using a single tube in the ARRL manual. Hence: Screen voltage 0V wrt earth Cathode voltage -325V wrt earth Grid Voltage -385V wrt earth Anode voltage +2700V wrt earth This gives the required 60V between cathode and grid and 325V between screen and cathode. Standing current is 250mA per valve (if my memory serves me correctly, since I haven't 'played' with it for a long time.) DC conditions seem okay, and the ampifier seems stable, with no hint of output with no drive, no matter where the tuning knobs are. It is not neutrilised. Applying RF drive, results in in output of about 100W, before the tubes start to draw grid current. Since the grid dissipation of these tubes is zero, it would not be safe (or linear) to run more output power than this. I have pushed the tubes to draw about 1mA of grid current each, where the output rises sharply, to about 600W. Since we were hoping for about 3200W output power, we clearly have some way to go!!! The power supply is designed so that it is possible to cut one valve off, so that the standing current of each valve can be set precisely equal by slight adjustment of the individual grid voltage. Cutting one valve off, then applying drive, again gives at most a few hundred Watts from one tube. One thing that has always bothered me, is that it is *poosible* that the tubes are being driven in push-pull (as I want), but the anode circuit is functioing in parallel (or visa-versa). Is there an easy way to check?? However, the fact it works poorly on one tube, with the other cut off, suggests this is not the problem. The grids are two half-wave lines. The anode is a 'U' shaped arrangement, with quarter wave lines. The Valves are at the ends, and HT fed to the centre. The output was supposed to be link coupled, much like many amps using twin 4CX250B's. I've virtually given up. Its cost nearly #2000 to build, but produces less output than a 4CX250B!! I can't see any way of getting it going properly. Any ideas????????? By the way, we have a decent power meter and 3kW oil cooled load. dave kirkby, G8WRB ------------------------------ Date: 24 Mar 1994 10:26:02 +0200 From: ihnp4.ucsd.edu!munnari.oz.au!hippo.ru.ac.za!nntp.und.ac.za!cs.uct.ac.za!cs.uct.ac.za!news@network.ucsd.edu Subject: advice fm To: ham-homebrew@ucsd.edu Hi Everyone. I'm looking for advice from someone knowledgable in radio and electronics. A normal f.m radio recieves up to about 108 Mhz. Does anyone know how to adjust it to recieve from 108 to about 130 Mhz? These are the aircraft frequencies and it'd be cool to listen in. I've heard that it's quite a simple operation involving a small adjustment in any cheap f.m reciever. Any advice is very welcome. Remember I'm a very non-specialist audience here, so please keep it simple. I'd appreciate mail in this regard. Thanks- -- Ari Cotton. ------------------------------ Date: Thu, 24 Mar 1994 23:32:35 GMT From: ihnp4.ucsd.edu!swrinde!cs.utexas.edu!utnut!utcsri!newsflash.concordia.ca!CC.UMontreal.CA!poly-vlsi!nick@network.ucsd.edu Subject: advice fm To: ham-homebrew@ucsd.edu In article <2mriqq$a0l@cs.uct.ac.za> acotton@cs.uct.ac.za (A Cotton) writes: >Hi Everyone. > ...stuff deleted... >These are the aircraft frequencies and it'd be cool to listen in. I've >heard that it's quite a simple operation involving a small adjustment in >any cheap f.m reciever. >Any advice is very welcome. Remember I'm a very non-specialist audience >here, so please keep it simple. Ok, Ari, here's simple, it will be tough to listen to the aircraft band on an FM receiver...mainly because they use AM (airplane mode). You'll need to get a VHF AM receiver if you want to listen to the tower... Nick *************************************************************************** * Nick Ciarallo * * SR Telecom Inc. telephone: 514-335-2429 ex: 438 * * Microwave Group facsimile: 514-334-7783 * * 8150 Trans Canada Hwy internet : nick@vlsi.polymtl.ca * * St. Laurent, Quebec hamradio : ve2hot@ve2fkb.pq.can.na * * Canada H4S-1M5 * *************************************************************************** * Accept no substitutes, *REAL* ham radio lives on 220 MHz! * *************************************************************************** ------------------------------ Date: 24 Mar 1994 10:34:38 GMT From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!howland.reston.ans.net!pipex!sunic!news.funet.fi!network.cc.jyu.fi!spt.fi!J.Pelt@network.ucsd.edu Subject: Component Databooks ? To: ham-homebrew@ucsd.edu HI ! I got recently a databook (Motorola.exe). And I think that it is really good. Would somebody tell me if there is other databooks in "computer format" available from other manufacturers ?? Is there FTP server somewhere, where i can get those files ? Thank you es 73 ! __________________________________________________________ Jukka Peltomaki J.Pelt@spt.fi Kaskenmaentie 139 HAM RADIO: OH1NVL 38770 LOHIKKO Finland, Europe ------------------------------ Date: 24 Mar 94 15:25:45 GMT From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!vixen.cso.uiuc.edu!aries!hawley@network.ucsd.edu Subject: Kenwood (TS-850) Computer Interface Info Wanted To: ham-homebrew@ucsd.edu adam@panix.com (Adam Epstein) writes: > A friend is interested in getting details about the computer >interface "box" used with the Kenwood TS-850. Has anybody built one >for themselves (rather than buying Kenwood's)? Does anybody have >schematics? I'm sure that recommendations of commercially available >software and other hints and kinks would be appreciated as well. >Email to me (adam@panix.com) and I'll forward your replies. > -Thanx > -Adam (N2DHH) The box is just opto isolators on the signal lines driven by and driving ttl to line driver level converters (5v to +/-10v). Look thru QST for an article.....it'll probably cost about the same if you do it right. Chuck Hawley KE9UW. ------------------------------ Date: Thu, 24 Mar 1994 15:59:47 GMT From: ihnp4.ucsd.edu!pacbell.com!att-out!nntpa!not-for-mail@network.ucsd.edu Subject: Kenwood (TS-850) Computer Interface Info Wanted To: ham-homebrew@ucsd.edu In article , Chuck Hawley wrote: >adam@panix.com (Adam Epstein) writes: > > >> A friend is interested in getting details about the computer >>interface "box" used with the Kenwood TS-850. Has anybody built one >>for themselves (rather than buying Kenwood's)? Does anybody have >>schematics? I'm sure that recommendations of commercially available >>software and other hints and kinks would be appreciated as well. >>Email to me (adam@panix.com) and I'll forward your replies. > >> -Thanx >> -Adam (N2DHH) >The box is just opto isolators on the signal lines driven by and driving >ttl to line driver level converters (5v to +/-10v). Look thru QST for an >article.....it'll probably cost about the same if you do it right. >Chuck Hawley KE9UW. > Check out my article in Feb. 93 QST "Everything You Always Wanted To Know About Computer-Controlling Modern Radios" (I didn't pick the title :). It has plans for a Kenwood interface that is opto-isolated and implements the handshaking lines as well as the data for complete compatibility. I also still offer the parts kits listed at the end of the article. Prices are the same, ($47 for Kenwood kit, $44 for Icom/Yaesu/Ten-Tec) but the address is now: CW Technology 7328 Timbercreek Court Reynoldsburg, OH 43068-1181 COD Orders Only (add $5) at 800-547-7479 The kits include PCB and all board mounted parts. You provide case and 8-15V supply. NOTE: ARRL has the PCB layouts and the parts are readily available - you do not have to buy anything from me. E-mail if you need more info -- Wally Blackburn Clinton-Gore - Socialist Leadership wrb@ccsitn.cb.att.com for the 90s! Amateur Radio Station AA8DX I'm the NRA. *More people have died in Ted Kennedy's car than from my gun!* ------------------------------ Date: Fri, 25 Mar 1994 06:37:16 GMT From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!newsserver.jvnc.net!raffles.technet.sg!ntuix!ntuvax.ntu.ac.sg!asirene@network.ucsd.edu Subject: Noise figure/transistors To: ham-homebrew@ucsd.edu Hi, Here's a design question. I am looking at the front-end RF amp which uses a 2N3904 and asking myself if I were to replace this with a transistor with a lower noise figure, say a 2N5179 or BF689, will I see any improvement? Is this mod worth pursuing? How much improvement can I expect to see here? Tks. Daniel ------------------------------ Date: Thu, 24 Mar 94 08:33:39 MST From: ihnp4.ucsd.edu!sdd.hp.com!news.cs.indiana.edu!lynx.unm.edu!dns1.NMSU.Edu!dns1.NMSU.Edu!usenet@network.ucsd.edu Subject: QSKing an AMP To: ham-homebrew@ucsd.edu On Fri, 18 Mar 1994 20:02:00 GMT, Kenneth L Florence wrote: >Hi all, I hv a Heath SB1000 (Ameritron AL80A), that I wud like to add QSK to. >ALl the QSK kits are a bit expensive for my taste, but I was wondering. Is it >just the speed of the internal relay that keeps this thing from being QSK? Afterreading Richard Measure's (SP?) article in QST, if I just replace the internal >relay with a high speed vacum relay (Jennings) will I be able to run it in QSK >or are there other restraints. Tnks for any help you can give. > >DE KA3PLS You can qsk with the jennings relays but you need some control circuits to prevent hot switching. If you find a diagram of an old alpha 77 that is exactly the scheme they used. 73 Bill AA5ZQ ------------------------------ Date: Thu, 24 Mar 1994 18:03:21 GMT From: rit!sunsrvr6!jdc@cs.rochester.edu Subject: Simple Tx/Rx? To: ham-homebrew@ucsd.edu Greg Segallis (gsegalli@ic1d.harris.com) wrote: : I want to build an RF remote shutter release for a camera. : I need a max range of about 50' and : it would be nice to have the receiver fairly insensitive to : unwanted noise. : I have seen several designs for simple transmitters (CW, tone : transmitters, etc.) They are simple (just a few parts, with : coils I can wind myself), small and cheap to build. They seem : to have adequate power for this application. : What I havn't seen is a simple receiver circuit. If you only need one (as opposed to manufacturing thousands), try a radio-controlled car transmitter/receiver/servo. I use one for kite aireal photography, and it works well. You only need one servo, so a 2-channel radio is more than enough. Look for ads in RC car/airplane magazines. Or better yet, buy a used RC car, and head down to the local hobby store for one extra servo. The extra servo goes on the camera, and you can move the receiver between the car and camera. Twice the fun for your money... Jim ------------------------------ Date: Thu, 24 Mar 1994 07:57:09 GMT From: ihnp4.ucsd.edu!galaxy.ucr.edu!library.ucla.edu!europa.eng.gtefsd.com!gatech!swrinde!cs.utexas.edu!csc.ti.com!tilde.csc.ti.com!mksol!blair@network.ucsd.edu Subject: What is third order intercept ? To: ham-homebrew@ucsd.edu Ronald Viegelahn (ron@etch-eshop.Berkeley.EDU) wrote: : Hi, : I keep hearing the term " third order intercept " when speaking : of frontend intermod problems. To further enhance your confusion... The voltage out vs voltage in 'transfer curve' can be modelled fairly well with a power series: Vout=A1*Vin + A2*Vin^2 + A3*Vin^3+... Ideally, A2,A3,A4,... = 0 and A1 is just the gain. But in reality A3 is large enough that if you input 2 tones they will beat against eachother and you'll wind up with 4 tones. If you dig out a table of trig identities and substitute V1*cos(2Pi*f1*t)+V2*cos(2Pi*f2*t) in for Vin you'll see the terms 2*f1-f2 and 2*f2-f1 fall out. Other tones fall out too, like the 3rd harmonics, but these are usually out of band. If V1 & V2 are large enough the 5th order terms 3f1-2f2 & 3f2-2f1 will pop up too and you'll have 2 more spurs show up. Usually the even order terms are insignificant since most linearities are symmetric and the spurs they produce fall out of band. 3rd order 2 tone spurs usually are the limiting factor in dynamic range calculations and are the bane of RF engineers. spuriously, Art. ------------------------------ End of Ham-Homebrew Digest V94 #72 ******************************