Date: Sat, 16 Jul 94 04:30:27 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 #197 To: Ham-Homebrew Ham-Homebrew Digest Sat, 16 Jul 94 Volume 94 : Issue 197 Today's Topics: 'Who was that masked capacitor?' FOLLOWUP/RETRACTION: Electronic Chemical Blues INFO. ON ANTIQUE ? LF Band experience? type-C RF connectors 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, 15 Jul 94 16:01:04 GMT From: news.cerf.net!gopher.sdsc.edu!nic-nac.CSU.net!charnel.ecst.csuchico.edu!yeshua.marcam.com!zip.eecs.umich.edu!newsxfer.itd.umich.edu!gatech!howland.reston.ans.net!math.@@ihnp4.ucsd.edu Subject: 'Who was that masked capacitor?' To: ham-homebrew@ucsd.edu In article tallath@hookup.net writes: > > I was wondering if any of you fine gentleman could answer a simple > question for me. I'm searching for what has been coined as a 'piston > trimmer' capacitor. Quite simply, it is a glass tube (usually 1/4" in diameter) that has been copper plated on the outside, with a thread adjustable inner part (piston) that acts as the second plate of a capacitor. 73 es GM from Jeff Amateur: WA6FWI@WA6FWI.#SOCA.CA.USA.NOAM | "You have a flair for adding Internet: jangus@skyld.grendel.com | a fanciful dimension to any US Mail: PO Box 4425 Carson, CA 90749 | story." Phone: 1 (310) 324-6080 | Peking Noodle Co. Hate "Green Card Lottery"? Want to help curb ignorant crossposting on Usenet? E-mail ckeroack@hamp.hampshire.edu for more information, or read news.groups. ------------------------------ Date: 15 Jul 1994 16:23:02 -0400 From: news.cerf.net!gopher.sdsc.edu!news.tc.cornell.edu!travelers.mail.cornell.edu!news.kei.com!MathWorks.Com!news2.near.net!bloom-beacon.mit.edu!ai-lab!bronze.lcs.mit.edu!@@ihnp4.ucsd.edu Subject: FOLLOWUP/RETRACTION: Electronic Chemical Blues To: ham-homebrew@ucsd.edu Thanks to those folks who suggested alternate chemicals and methods to use, but first, an apology: As Henry Spencer and a few others have pointed out, there isn't a conspiracy against individual servicers; my experiences were just due to some unfortunate timing on my and the EPA's part. Henry's quite right that the CFC regulations have affected large companies as well. (To the guy that called me empty-headed, I'm really sorry--I forgot about Halon.) As Henry says, all CFC solvents are to be eliminated in a few years (1996?), and the existing chemicals are being slowly phased out. The current patchwork regulations of what can be sold to whom is a cause for much confusion and consternation for myself, others, and (I suspect) vendors such as MCM. I don't care to argue the ozone matter; CFC's are going away, and I'm just trying to find subsitutes that are safe as possible for the ozone *and* myself. I'm not interested in stockpiling; I don't want to store large quantities of *any* chemical in my house. I'm not necessarily averse to using petroleum-based products; as I mentioned previously, I use acetone (yes, people, I *know* it eats plastic! Voice of experience? Nah! :)) and isopropanol. Both of these are flammable, but I've been using them for awhile and I can (IMHO) control the risks. I'd like that any chemical I buy not have much more risk than the ones I mentioned. (I don't clean with kerosene; why should I bear the fire risk from a like solvent if I don't need to?) One thing I thought of: Except for compressed air, why do we need aerosol cans at all? I usually use the cans to spray short bursts with an extension tube, or spray into a paper towel, foam swab or Q-tip. I'd be perfectly happy, for my purposes, with a pump-bottle. (I'm not sure this would work for freeze spray, but it's still one less can on my shelf.) If it removed the risk of a flammable propellant, I'd be relieved. I'd recommend that *anyone* on this group who buys chemicals read the fine print on the can and ask questions, CFCs or not. There's an interesting article in the current issue of ELECTRONIC SERVICING AND TECHNOLOGY that covers this very subject, quite timely. ("Electronic Servicing for Performance and Reduced Environmental Impact", Dr. Mo Tazi, p.20) ...Dave -- | David Moisan, N1KGH /^\_/^\ moisan@silver.lcs.mit.edu | | 86 Essex St. Apt #204 ( o ^ o ) n1kgh@amsat.org | | Salem. MA 01970-5225 | | ce393@cleveland.freenet.edu | | | ------------------------------ Date: Fri, 15 Jul 1994 22:27:49 GMT From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!gatech!nntp.msstate.edu!olivea!sgigate.sgi.com!odin!ukcsd.reading.sgi.com!statham_j@network.ucsd.edu Subject: INFO. ON ANTIQUE ? To: ham-homebrew@ucsd.edu Some time ago, I became the proud owner of a receiver built in the 1920s (?) by an uncle of my father. I am told that it was built from a magazine article and was called The Foreign Listeners Four because at that time it could receive four foreign stations - from the UK. It's a fascinating piece of Meccano built on a wooden board and housed in what I think was once the case of a floor standing wind-up gramaphone. It consists of four pin triodes with screw terminal bases and is hooked together with square sectioned, rubber coated wire. Can anyone give me any information on my fossil ? Or does anyone know a living fossil who might of heard of it ? What I'd really like to do is get it going again and to have a copy of the original magazine article would be fascinating. Please email me with replies as my access to News is only as reliable as the next mod I make to the bridge I'm using. Thanks John -- John Statham statham_j@reading.sgi.com Silicon Graphics Laser House Tel: (0)61-428-1559 Salford Quays Manchester United Kingdom Yes, perhaps I have lost my mind, but I should have a backup on tape somewhere. ------------------------------ Date: 15 Jul 94 18:24:24 GMT From: news-mail-gateway@ucsd.edu Subject: LF Band experience? To: ham-homebrew@ucsd.edu Running FM in the LF (LowFER) band is pretty easy... but doing so effectively depends on what you intend to do and how you intend to do it. If you wish to go a short distance (a few miles at most, more likely, not more than a block or two) then FM would be a dismal choice (I would take it that you are talking about FM voice...) for several reasons: - It takes up massive bandwidth. For standard 3 KHz deviation FM voice, expect to require about 12 KHz or so. You can't do the old idea of "I don't need 3 KHz deviation... If I deviate only 1 KHz or 500 Hz, then I'll take a LOT less bandwidth..." If you think this will work, then re-read about FM... - If you FM is Ok (i.e. you can live with the wide bandwidth, the very high noise levels (especially in urban areas...) (Oops... I meant to say "If for you FM is OK...") then you have to consider the matching network. A LowFER antenna system is typically a base-loaded tophatted vertical with a VERY good ground system. As with any heavily-loaded antenna the loading coil (in this example) is likely to be your primary loss factor. A wire coil of heavy-guage wire (14 or 12) would work, but Litz wire (remember that?) such as 12/40 (#12 with strands of #40) will work very well if its geometry is appropriate (i.e. a basket-weave coil to minimize its distributed capacitance which would spoil its Q, thereby efficiency...) So, if you build a half-decent coil (to acheive half-decent power transfer) then you are talking about very high Q. I ran some SSB on the Lowfer band for a while and using a coil that wasn't really all that great, I could hear 'sideband cutting' as I tuned through resonance. In fact, I had to retune if I changed from upper to lower sideband. The point is that an SSB signal taking only 2.5 KHz or so *is* 'colored' by the tuning network. Imagine what would happen (response-wise, not to mention phase-wise to an approx. 10 KHz wide FM signal...) If it is voice communications that you want, there are lots of reasons why SSB (or even AM...) may be better suited than FM on this band... That's not saying that it can't be done, but one should keep in mind the contradicting requirements/realities. There *are* ways to broaden the bandwidth at these frequencies without killing efficiency (Radio Warsaw, Poland has an LF transmitter in the 150 KHz range and it has typical european AM/LF broadcast bandwidth on its transmissions, about 10-12 KHz or so, at least...) but I'll be darned if I can remember how it was done, or where I saw its desicription. A good book on all of this is 'VLF Radio Engineering' by Watt. It was published in the late 60's and it is in most larger libraries... Internet: clint@uugate.aim.utah.edu Amprnet: ka7oei@uugate.wa7slg.ampr.org ------------------------------ Date: 15 Jul 1994 16:41:31 GMT From: noc.near.net!sunfish.hi.com!brainiac.hi.com!user@uunet.uu.net Subject: type-C RF connectors To: ham-homebrew@ucsd.edu In article , fred-mckenzie@ksc.nasa.gov (Fred McKenzie) wrote: > As far as airflow is concerned, are there any active components involved? > What generates heat? If the multicoupler has only passive, high-Q > components, the cooling air may have been required for very high RF power > levels. For low power, it may not be needed. The receiver multicoupler has a two-transistor RF preamp per output to make up for losses in the hybrid splitters. These transistors probably run at a high bias current for better IMD performance. (They are TO-5 cased, and have clip-on heatsink fins. Some have "TRW 02"markings on top.) The mechanical design of the enclosure for this beast does not provide for convection-cooling. It has only a small inlet slot on the right side, and a larger outlet slot on the left side. I expect that the power dissipation isn't all that high, but without forced-air cooling, the transistors probably wouldn't last long. Steve Byan internet: steve@hi.com Hitachi Computer Products (America), Inc. 1601 Trapelo Road phone: (617) 890-0444 Waltham, MA 02154 FAX: (617) 890-4998 ------------------------------ End of Ham-Homebrew Digest V94 #197 ******************************