Date: Sat, 12 Feb 94 04:30:08 PST From: Ham-Ant Mailing List and Newsgroup Errors-To: Ham-Ant-Errors@UCSD.Edu Reply-To: Ham-Ant@UCSD.Edu Precedence: Bulk Subject: Ham-Ant Digest V94 #30 To: Ham-Ant Ham-Ant Digest Sat, 12 Feb 94 Volume 94 : Issue 30 Today's Topics: 75 ohm twinlead Antenna Erection Aids Antenna for Sale BALUN FOR 2-M YAGI Cushcraft R7 antenna to trade... How to increase antenna sensitivity? J-Pole Design Needed Need Wideband RX antenna recommendation new radio communications mailing list Quagi RG8 & PL259 SWL RX Antenna (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-Ant Digest are available (by FTP only) from UCSD.Edu in directory "mailarchives/ham-ant". 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: Tue, 8 Feb 1994 01:40:57 GMT From: ucsnews!sol.ctr.columbia.edu!howland.reston.ans.net!vixen.cso.uiuc.edu!sdd.hp.com!hpscit.sc.hp.com!cupnews0.cup.hp.com!news1.boi.hp.com!hp-pcd!hpcvsnz!tomb@network.ucsd.edu Subject: 75 ohm twinlead To: ham-ant@ucsd.edu Claude Frantz (claude@bauv.unibw-muenchen.de) wrote: : Amphenol number 214-023: 75 ohm oval type twin-lead transmission : line capable of handling 1 kW of RF power in amateur applications. : Conductors: 7 AWG-21 copper. With no loss in the insulation and assuming smooth conductors with the same cross-section, the loss at 14MHz would be expected to be about 0.58dB/100ft. However, expect about 10% higher loss because of the stranded wire, and possibly higher loss if the line is wet. This is a bit better than RG-213, but not as good as 9913. : There is a low power type too: Amphenol number 214-080, 7 AWG-28 : tinned copper. No information about power rating. Same assumptions about the wire lead to about 1.3dB/100 feet for this stuff. In both cases, the attenuation scales directly as the square root of frequency. If you multiply the frequency by 2, multiply the attenuation _in_dB_ by 1.41. Conclusion: you don't do this to get low loss. (Most loss in lines at HF is I^2 * R. To get the loss down, lower the effective R by making the conductors larger, or lower the I by making the impedance higher. That's how high impedance open line gets low loss: the same R at 600 ohms dissipates lots less than at 50 ohms.) 73, K7ITM ------------------------------ Date: 8 Feb 94 00:20:02 GMT From: netcon!bongo!skyld!jangus@locus.ucla.edu Subject: Antenna Erection Aids To: ham-ant@ucsd.edu In article <1994Feb6.144242.14808@bongo.tele.com> julian@bongo.tele.com writes: > For those appliance operators that would like the catapult > and reel option but lack the motivation or skills to attach a $10.00 > reel to a $10.00 catapult with $00.02 of duct tape there is a > solution. > Why, in my day, we used to have to raise our own cats and ducks. Finding the pults was a tad tricky, but could be done with the skillful adaptation of a snipe bag. Amateur: WA6FWI@WA6FWI.#SOCA.CA.USA.NA | "It is difficult to imagine our Internet: jangus@skyld.tele.com | universe run by a single omni- US Mail: PO Box 4425 Carson, CA 90749 | potent god. I see it more as a Phone: 1 (310) 324-6080 | badly run corporation." ------------------------------ Date: 10 Feb 94 15:15:00 -0500 From: blkcat!1-109-239-0!Scott.Snyder@uunet.uu.net Subject: Antenna for Sale To: ham-ant@ucsd.edu Alpha 60' sloper antenna and 75' of coax cable for sale. Best offer. If interested, leave me a message with offer and phone number. I'll call back. (703) 816-7823. ------------------------------ Date: Thu, 10 Feb 1994 15:41:06 GMT From: spsgate!mogate!newsgate!dtsdev0!kinzer@uunet.uu.net Subject: BALUN FOR 2-M YAGI To: ham-ant@ucsd.edu (Hugh Shane N7UAX) writes: +Can anyone suggest a design for matching a 50-ohm coax feed to a six beam, +2 meter Yagi. The balun designs I've seen all seem to be restricted to +frequencies less than 100MHz. There must be a classic technique, I just +can't find it! Gamma Match? -dave ------------------------------ Date: 10 Feb 1994 16:36:16 GMT From: src.dec.com!src.dec.com!estrella@decwrl.dec.com Subject: Cushcraft R7 antenna to trade... To: ham-ant@ucsd.edu ********************************************************* Posting for my brother who doesn't have an account... I have a cushcraft R7 vertical antenna I want to trade for a good working HF solid state transceiver; I can make up some cash with the antenna if necesary. I can be reached at ( 408 ) 279-6028 evenings and weekends. Luis Estrella KD6VTZ TRADE ONLY ********************************************************** Or you can send me e-mail and I will give Luis your message. John Estrella ------------------------------ Date: Tue, 8 Feb 1994 14:23:56 GMT From: agate!howland.reston.ans.net!vixen.cso.uiuc.edu!uchinews!dionheinz.uchicago.edu!sweeney@network.ucsd.edu Subject: How to increase antenna sensitivity? To: ham-ant@ucsd.edu For AM broadcast, receiver attennas are usually wirewound ferrite cores. Could someone explain to me how these work or give me a pointer to a reference? I know they are directional and I think they somehow couple with the magnetic field of the broadcast signal. How are they designed? How are they built? How are they tuned? Would tuning to a single station help reception? In article <1994Feb7.041619.3604@cmkrnl> you write: >In article <2j4n1i$gje@blaze.cs.jhu.edu>, Michael Young Ko writes: >> Does anyone know how those AM Radio Signal amplifiers work? >> I remember seeing one a couple of years back and it was this large >> cylinder about 6" thick. Any ideas? > >Most of them aren't "amplifiers", they're just antennas that are much bigger >than the ones built into most portables. Which isn't to say that they don't >work -- they do. Very well. > >The general answer to "how to make an antenna more sensitive" is: > > - Make it bigger. (But still resonant at the freq of interest, if > possible.) > > - Get it up higher. (But not so high that the losses in the lead > wire cancels the gains from increased height.) > > --- Jamie Hanrahan, Kernel Mode Systems, San Diego CA >Internet: jeh@cmkrnl.com (JH645) Uucp: uunet!cmkrnl!jeh CIS: 74140,2055 -- Jeff sweeney@dionheinz.uchicago.edu ------------------------------ Date: Tue, 8 Feb 1994 01:09:22 GMT From: spsgate!mogate!newsgate!nuntius@uunet.uu.net Subject: J-Pole Design Needed To: ham-ant@ucsd.edu In article <2irlta$9o3@gaia.ucs.orst.edu> Ray Stein, steinr@ucs.orst.edu writes: >Though it is not made only of just coax, I highly recommend using >a twin-lead TV antenna J-Pole design. I will describe briefly how >it is made: > >Starting at the bottom, short the two leads together. Cut a section of >about 55 inches total for the antenna. From the short up to 1.25 inches, >connect your standard 50 ohm coax. On one side only up 16.5 inches from >short, cut a .25 inch chunck out. It's done! > >Trim the top for desired SWR. Good luck! > >--Ray Stein Has anyone tried this type of J pole as a dual band antenna. I have a "copper cactus" and it works well on both 2mtr and 70 cm......I am looking for a good dual band antenna for my suzuki sidekick. The problem is the lack of a good ground plane. Another design point is I would like it to fit through the garage door. I can mount it fairly low towards the bumper if required. Thanks for the help. Rick Aldom ------------------------------ Date: 11 Feb 94 17:01:29 GMT From: news.tek.com!gvgpsa.gvg.tek.com!gold.gvg.tek.com!gvgadg.gvg.tek.com!groverc@uunet.uu.net Subject: Need Wideband RX antenna recommendation To: ham-ant@ucsd.edu In article <2jb9pk$h37@hp-col.col.hp.com>, writes: > > I would like to have an antenna I can mount on my house that can pick up > signals from 25 or 50MHz on up to 905 MHz. The antenna would be a > receive only proposition (for scanning, etc.). > > Any recommendations? > Check out a discone. RS sells one that is quite useable. About $60 Grover WT6P ------------------------------ Date: Fri, 11 Feb 94 16:39:10 -0500 From: spool.mu.edu!howland.reston.ans.net!europa.eng.gtefsd.com!news.umbc.edu!eff!news.kei.com!yeshua.marcam.com!charnel!olivea!news.bu.edu!noc.near.net!news.delphi.com!usenet@munnari.oz.au Subject: new radio communications mailing list To: ham-ant@ucsd.edu Yes, please, info to A. Noble, PO Box 189490, Sacramento, CA 95818.Thanks ------------------------------ Date: 10 Feb 1994 19:37:09 GMT From: ucsnews!newshub.sdsu.edu!usc!howland.reston.ans.net!sol.ctr.columbia.edu!news.kei.com!newsstand.cit.cornell.edu!newsstand.cit.cornell.edu!usenet@network.ucsd.edu Subject: Quagi To: ham-ant@ucsd.edu In article Tom Bruhns, tomb@lsid.hp.com writes: >(I added the "between elements" column.) >I built one of these, and always wondered about the spacing. Is >that spacing between the 2nd and 3rd director right?? It looks >"funny"... Guess I could measure the gain and see if it's OK. >From memory, Christie's posting looks like what I built, so I'm >questioning the original article, not the posting. > >73, K7ITM I've always wondered about that myself. But I've built about a dozen quagis now on 2 meters and 440 for satellites and atv and they do match up and do seem to work and work well, so I 've stopped worrying about it. But it certainly does look odd compared to a yagi for a similar band set next to it. Has anybody ever asked Overbeck where the dimensions came from? The original articles inicated that it was sort of arrived at empirically. BTW, in the interest of making a reasonable sized beam on 2 once, I built the two loops per spec and then started adding directors. SWR was bloody awful till the second directory went on, then it was just bad. But with the 3rd director it tamed down considerable and started looking normal. Directors beyond that didn't seem to have much effect on swr. So I tell people building them to be sure to have at least 3 directors on after the loops, after that I adjust according to gain needed and boom length available/tolerable. YMMV. Kevin, WB2EMS ------------------------------ Date: Fri, 11 Feb 1994 20:35:42 GMT From: agate!howland.reston.ans.net!math.ohio-state.edu!sdd.hp.com!col.hp.com!srgenprp!alanb@network.ucsd.edu Subject: RG8 & PL259 To: ham-ant@ucsd.edu HILLIER, MARK D. (md_hill@pavo.concordia.ca) wrote: : ... By the way, RG-8 is terrible cable, I hope you are using it indoors, : because it won't last outside. Not necessarily. If you can find RG-8 made to the original military specs, it is very good cable indeed. (A brand name like Belden should be safe.) Unfortunately, as you say, much of the stuff masquerading these days under the name "RG-8" is junk. AL N1AL ------------------------------ Date: 10 Feb 1994 15:19:41 GMT From: ucsnews!sol.ctr.columbia.edu!xlink.net!scsing.switch.ch!swidir.switch.ch!univ-lyon1.fr!elendir@network.ucsd.edu Subject: SWL RX Antenna To: ham-ant@ucsd.edu Hello, one of my friend has got involved in SWL. He is on his way to buy a RX rig, but he still wavers about the antenna to use. So, what would be the best antenna for listening to almost all frequencies below 30 MHz ? I thought of a quad loop, a delta or something like a log-periodic, but the antenna has to be (as best as possible) omnidirectional ! Or directional but easily movable. Thanks for any advice. Vincent (10 weeks, and still waiting...) -- ------------------------------ Date: 10 Feb 94 22:56:53 GMT From: mulvey!rich@uunet.uu.net Subject: SWL RX Antenna To: ham-ant@ucsd.edu Elendir (elendir@enst.fr) wrote: : Hello, : one of my friend has got involved in SWL. He is on his way to buy a RX : rig, but he still wavers about the antenna to use. So, what would be the : best antenna for listening to almost all frequencies below 30 MHz ? I : thought of a quad loop, a delta or something like a log-periodic, but the : antenna has to be (as best as possible) omnidirectional ! Or directional but : easily movable. : Thanks for any advice. How about a simple fan-dipole? Extremely cheap and easy to make for the major SW broadcast bands. - Rich -- Rich Mulvey Amateur Radio: N2VDS Rochester, NY rich@mulvey.com "Full power on half a watt." ------------------------------ End of Ham-Ant Digest V94 #30 ****************************** ******************************