Date: Fri, 2 Sep 94 04:30:11 PDT 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 #291 To: Ham-Ant Ham-Ant Digest Fri, 2 Sep 94 Volume 94 : Issue 291 Today's Topics: 6 meter antenna????HELP!!! AC House wiring used as antenna? apartment antennas Ball mount summary CB antenna questions. CB omnidirectional ant. as Ham ant. Does SWR change... (3 msgs) GAP antenna One-way propagetion? Q: slitted tube antennas z 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: Wed, 31 Aug 1994 18:09:58 GMT From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!usenet.ins.cwru.edu!news.csuohio.edu!vmcms.csuohio.edu!R0264@network.ucsd.edu Subject: 6 meter antenna????HELP!!! To: ham-ant@ucsd.edu In article <33vmr5$mpc@usenet.INS.CWRU.Edu> ah157@cleveland.Freenet.Edu (Rob Henry) writes: > > > >Coulds soeone reccomend an antenna for 6 meters fm? >homemade or bought, any sources or ways to make one./ >I tried winding a half wavelength around pvc pipe,one ground and one positive >rf but it does not seem to work all that well. >leave mail please. >rob >kb8sqh Why not start with a plain dipole? What purpose does the helical winding serve -- shortening? A 6-meter dipole should be pretty short (11 feet?) without helical winding. If you want it vertical, just hang one end with a string and insulator, from something like a tree branch, and bring the coax away at right angles for at least a quarter wave length, about 6 feet should do it. Maybe there is some constraint that you did not tell us about. ---- Phil Emerson, AA8JO. email: R0264@vmcms.csuohio.edu ------------------------------ Date: 1 Sep 1994 04:27:01 GMT From: ihnp4.ucsd.edu!dog.ee.lbl.gov!overload.lbl.gov!agate!howland.reston.ans.net!gatech!udel!news.sprintlink.net!sundog.tiac.net!max.tiac.net!rblaine@network.ucsd.edu Subject: AC House wiring used as antenna? To: ham-ant@ucsd.edu I have seen adapters that plug into an AC outlet in a house which use the houses's AC wiring as an antenna. Would this work? I am interested in this mainly for use on a CB, but I'm also interested in it for general scanner use. Any advice or comments appreciated. -- |--------------------------------------------------------------------| | ---- Russ Blaine ---- | Plane #6933 |"Achilles was dipped in | | | ______ | the River Stynx until | | rblaine@tiac.net | --)=Cannibal--> | he became intolerable."| |--------------------------------------------------------------------| ------------------------------ Date: 31 Aug 1994 22:51:06 -0400 From: newstf01.cr1.aol.com!search01.news.aol.com!not-for-mail@uunet.uu.net Subject: apartment antennas To: ham-ant@ucsd.edu In article <94240.092424JBAACK31@MAINE.MAINE.EDU>, writes: Have you tried the AEA Isoloop? It doesn't take much space, and performs very well on 10-30. ------------------------------ Date: 1 Sep 1994 02:22:57 GMT From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!gatech!udel!news.sprintlink.net!indirect.com!grizzarv@network.ucsd.edu Subject: Ball mount summary To: ham-ant@ucsd.edu I posted a question about ball mounts with either: 1) teeth to anchor the ball in place on the insulator, or 2) a stud with a left-hand thread. It appears there are no such beasts. Ah well - the guy wasn't too obtrusive. It's going back on. de kg7yy ------------------------------ Date: 1 Sep 1994 04:13:17 GMT From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!gatech!udel!news.sprintlink.net!sundog.tiac.net!max.tiac.net!rblaine@network.ucsd.edu Subject: CB antenna questions. To: ham-ant@ucsd.edu Here's my situation: I just bought a 5-watt radio shack CB and a magnetic mount mobile CB antenna. I also bought an SWR meter. I hooked it all up and it worked fine, so i started adjusting the antenna according to the manual that came with it to get peak performance. I hooked my SWR meter up, calibrated it, and got about 1.6 on channel 1 and 3.2 on channel 40. So I started trimming the antenna down. I probably took about 1/2" - 3/4" off of the length, and ended up with about 1.1 or 1.0 on channel 1 and 2.4 on channel 40. Should I keep going to get channel 40 down? Did I go too far? Another question: People on the airwaves report my signal to me in "pounds". Someone 1-3 miles away said I was coming in at about 6 or 7 pounds. I was talking to someone 10-15 miles away as well with limited success and to someone 4 or 5 miles at 3 pounds. What is a "pound"? Will this increase as my SWR ratios improve? Will my range decrease significantly as a result from the antenna trimming? Thanks for your help.. reply by email if possible. -- |--------------------------------------------------------------------| | ---- Russ Blaine ---- | Plane #6933 |"Achilles was dipped in | | | ______ | the River Stynx until | | rblaine@tiac.net | --)=Cannibal--> | he became intolerable."| |--------------------------------------------------------------------| ------------------------------ Date: Wed, 31 Aug 1994 18:24:47 GMT From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!usenet.ins.cwru.edu!news.csuohio.edu!vmcms.csuohio.edu!R0264@network.ucsd.edu Subject: CB omnidirectional ant. as Ham ant. To: ham-ant@ucsd.edu In article interso@cam.org (Archibald d'Arsenic) writes: > >I have a 18 feet long omnidirectional base station antenna (SOLARCON A-99) >mounted on the roof of my house. It was installed for CB. > >But, it is possible to use it for SWL? > >If yes, it is possible to use it for CB transceiving and SWL. >There is an bi antenna tuner for using the antenne on both application. > >Thanks for your help. > >You can reply to >interso@cam.org Presumably, it will work for CB transceiving, if that is what it was installed for. You can test that function easily enough, I would think. If so, it can be used for SWL too, maybe with a couple of tricks, depending on the frequencies of interest. It might not be the best SWL antenna, but you will pick up something. Here are some tricks to try for SWL. (1) try it with just the center conductor of the coax connected to your SWL rig. (2) connect the center conductor and the shield together, and both to your SWL rig. You should not need an antenna tuner for using the antenna with CB. If you want to use an antenna tuner for SWL, you don't need a heavy duty one. Actually, I doubt if a tuner will help much with SWL anyway, but it might. -- Phil Emerson, AA8JO, email: R0264@vmcms.csuohio.edu ------------------------------ Date: Wed, 31 Aug 94 13:23:00 -0500 From: ihnp4.ucsd.edu!ucsnews!newshub.sdsu.edu!nic-nac.CSU.net!usc!howland.reston.ans.net!agate!iat.holonet.net!cencore!forrest.gehrke@network.ucsd.edu Subject: Does SWR change... To: ham-ant@ucsd.edu CE>I have been challenged to prove that SWR can change radically CE>with transmission line length, so here is my actual antenna... CE>Xmtr--->50 ohm--->Rg58-->1/1 balun---->450 ohm---->50 ohm resonant CE> SWR meter Ladder-Line Antenna CE>Assumptions: Transmission lines are lossless. SWR meter is reading CE>the actual SWR. Balun is a perfect transformer. CE>1. If the ladder-line is an even number of electrical half-wavelengths, CE>the SWR meter will read 1/1. CE>2. If the ladder-line an odd number of electrical quarter-wavelengths, CE>the SWR meter will read 81/1. ((450/50)*450)/50 CE>On 28.4 MHz, changing the ladder-line length by about ten feet can cause CE>the SWR on the coax to change from 1/1 to 81/1. Who was it who said that CE>can only happen in a fantasy world? Ye Gods and little fishes! Cecil, you ARE living in a fantasy world. Either that or you are trying a bait and switch on us and hoping nobody notices. If you are serious and I will assume you are, consider the experiment you have set up. 1. You have an even number of half-waves 450 ohm line with a 50 ohm load attached. Result: you present to the 50 ohm coax a 50 ohm load and you measure 1:1 SWR (assuming no loss), regardless of the length of the 50 ohm line. 2. You have an odd number of quarter-waves 450 line with a 50 ohm load attached. Result: you present to the 50 ohm coax a 4050 ohm load and you measure 81:1 SWR, (again assuming no loss) and it will be so anywhere along that 50 ohm line. The ladder line is simply our old familiar 1/4 wave impedance transformer. Now, look at which line you changed the length. It wasn't the 50 ohm line. If you had an SWR meter calibrated for 450 ohms, it would have shown a 9:1 SWR regardless of your changing the length of that ladder line. But for the 50 ohm line you merely presented two different loads and got the result you asked for. C'mon Cecil, get real. This is bogus! CE>73, Cecil, KG7BK, OOTC (Not speaking for Intel) That disclaimer is appropriate. I would sure hope Intel wouldn't subscribe. --k2bt --- ³ SLMR 2.1a ³ On the 8th day God said "SWR constant all along line". ------------------------------ Date: 31 Aug 1994 20:08:40 GMT From: ihnp4.ucsd.edu!news.cerf.net!gopher.sdsc.edu!news.tc.cornell.edu!travelers.mail.cornell.edu!news.kei.com!ssd.intel.com!chnews!news@network.ucsd.edu Subject: Does SWR change... To: ham-ant@ucsd.edu In article <342bfq$6r1@charm.magnus.acs.ohio-state.edu> Bob_Dixon@osu.edu writes: >This is an invalid example. An invalid example of what? This is my exact antenna. The SWR in the coax changes with changes in the length of the ladder-line. I had to add 6 ft. of ladder-line to get a match on 10m. This is the same configuration as many G5RV's and changing the length of the 300 ohm portion of the G5RV will definitely have a radical effect on the SWR at the transmitter end of the 50 ohm coax. (The two sections of transmission line form a series-section transformer). >The SWR in the ladder line is the same no matter how long it is, and >that is the only thing of relevance in your example. The 450/50 value in my equation is the SWR on the ladder-line and it is constant. It is the SWR in the coax that we are measuring and it varies wildly with minor changes in the length of the ladder-line. >if you leave the coax load constant (same antenna and same length ladder >line), then the swr in the coax does not vary if you change its length. That's true if one assumes lossless transmission lines. In reality, with my G5RV on 17m, the SWR meter at the transmitter end of the 70 ft run of RG-58 measured 5/1. That means the SWR at the coax/ladder-line junction was 20/1. If I halved the length of coax, I would measure an SWR of 8/1 at the transmitter end. Do you disagree? This is not aimed at the antenna "gurus" except to ask you guys to please be more careful with your all-encompassing declarations. 73, Cecil, KG7BK, OOTC (Not speaking for Intel) -- Intel, Corp. 5000 W. Chandler Blvd. Chandler, AZ 85226 ------------------------------ Date: 1 Sep 1994 04:40:12 GMT From: pa.dec.com!nntpd.lkg.dec.com!iamu.chi.dec.com!little@decwrl.dec.com Subject: Does SWR change... To: ham-ant@ucsd.edu In article <340v8a$pbh@chnews.intel.com>, Cecil_A_Moore@ccm.ch.intel.com writes: |>I have been challenged to prove that SWR can change radically |>with transmission line length, so here is my actual antenna... |> |>Xmtr--->50 ohm--->Rg58-->1/1 balun---->450 ohm---->50 ohm resonant |> SWR meter Ladder-Line Antenna |> |>Assumptions: Transmission lines are lossless. SWR meter is reading |>the actual SWR. Balun is a perfect transformer. |> |>1. If the ladder-line is an even number of electrical half-wavelengths, |>the SWR meter will read 1/1. |> |>2. If the ladder-line an odd number of electrical quarter-wavelengths, |>the SWR meter will read 81/1. ((450/50)*450)/50 |> |>On 28.4 MHz, changing the ladder-line length by about ten feet can cause |>the SWR on the coax to change from 1/1 to 81/1. Who was it who said that |>can only happen in a fantasy world? This is because the line is not matched to the source. In your case you have built a series-section transformer. No one is going to argue that a transmission line with a characteristic impedance differs from the source and load is not going to affect the SWR as measured at the source when its length is varied. Pick up a copy of either the ARRL Antenna Book, or Maxwell's book called Reflections. Either will explain what is happening in the above circuit. 73, Todd N9MWB ------------------------------ Date: 31 Aug 1994 22:20:30 -0400 From: uunet.ca!uunet.ca!io.org!nobody@uunet.uu.net Subject: GAP antenna To: ham-ant@ucsd.edu I have used a GAP antenna for the last three years and have some comments although I have no experience with the Titan. Compared to the R7, the GAP cannot be adjusted or tuned. It is really a dipole with matching rods and in a single antenna version will produce unity gain at best. My GAP results in reasonable SWR only while planted in the ground and installed even 10 ft above ground sent the SWR to 3 or more. Finally the DX-VI which I have results in heard signals of 10db less than a wire dipole in the same location. Transmitted signals result in several S units less to the same receiving station. Having said all that, the antenna is well built and works as described. I have confirmed over a hundred countries with it and during better portions of the solar cycle works very well. I would recommend it as a good antenna for those of us with small city lots and smaller budgets. hope that helps de VE3SVL dave ------------------------------ Date: 30 Aug 1994 10:04:56 GMT From: ihnp4.ucsd.edu!agate!doc.ic.ac.uk!bright.ecs.soton.ac.uk!pdh@network.ucsd.edu Subject: One-way propagetion? To: ham-ant@ucsd.edu In <33l9l3$1a2i@info2.rus.uni-stuttgart.de> deap1032@servus11.rus.uni-stuttgart.de (Bruegemann) writes: >Or are there scattering effects that work only one way? There shouldn't be, no-one has suggested a believable mechanism, but I've heard this often enough to believe in it. -- [] Peter Harris, Optoelectronics Network Supervisor, Southampton University [] "Sir, you will either die on the gallows or of the pox !" "That, my Lord, depends on whether I embrace your principles or your mistress" John Wilkes to The Earl of Sandwich, Parliament, November 1763 ------------------------------ Date: Wed, 31 Aug 1994 12:26:01 UNDEFINED From: ihnp4.ucsd.edu!ucsnews!newshub.sdsu.edu!nic-nac.CSU.net!usc!howland.reston.ans.net!EU.net!Germany.EU.net!netmbx.de!midas.cellware.de!wsw.cellware.de!wsw@network.ucsd.edu Subject: Q: slitted tube antennas To: ham-ant@ucsd.edu Hello out there! I have heard, that some kind of slitted tube can be used as an antenna. Could anybody tell me, where to find some documentation and formulae about this? I think they should be very robust and good for areas with strong winds? Thanks for your help. 73µs Stefan (DD6FM @ DB0GR) ------------------------------ Date: 31 Aug 94 21:30:31 -0500 CST From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!math.ohio-state.edu!darwin.sura.net!CrystalData.COM!americon!B._Paul_Palmer@network.ucsd.edu Subject: z To: ham-ant@ucsd.edu From: Paul.Palmer@pcs.huntsville.al.us (B. Paul Palmer) Reply-To: Paul.Palmer@pcs.huntsville.al.us --- Paul (Cliffy) Palmer / KE4IDG Palmer Computer Solutions P.O. Box Madison, AL 35758 ------------------------------ Date: 1 Sep 1994 04:44:11 GMT From: pa.dec.com!nntpd.lkg.dec.com!iamu.chi.dec.com!little@decwrl.dec.com To: ham-ant@ucsd.edu References <1994Aug25.020651.196034@zeus.aix.calpoly.edu>, , <1994Aug30.221703.28609@miavx1> Reply-To : little@iamu.chi.dec.com (Todd Little) Subject : Re: Does 73 Magazine have high SWR? In article <1994Aug30.221703.28609@miavx1>, vgblackwell@miavx1.acs.muohio.edu (V. George Blackwell) writes: |>u> I found an older ('65) ham projects book in our campus library which |>> spoke of using lamp (`zip') cord as an antenna lead in. It works. |>> Tubes could withstand a lot of punishment. I wouldn't expect any |>> modern book to suggest using zip cord, for the transistors in your |>> final are rather `sensitive'. Thus, your `duh' comment is answered. |>> |>> Jeff NH6IL |> |>Lamp cord has a surge impedance of aprox. 72 ohms. |> |>Good luck |> |> Sure you can use zip cord and its impedance isn't necessarily 72 ohms. Lamp cord is fairly variable and its impedance should be measured if you want to determine its effect on your antenna system. Also remember that it's not likely to be a particularly low loss feedline. 73, Todd N9MWB ------------------------------ End of Ham-Ant Digest V94 #291 ******************************