Date: Sun, 12 Dec 93 04:30:19 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 V93 #140 To: Ham-Ant Ham-Ant Digest Sun, 12 Dec 93 Volume 93 : Issue 140 Today's Topics: Mag North Vs True North (2 msgs) PI vs T Transmatch Circuits short sw antennae? T2FD antenna: any experiences? (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: Sat, 11 Dec 1993 16:04:30 GMT From: library.ucla.edu!europa.eng.gtefsd.com!emory!kd4nc!ke4zv!gary@network.ucsd.edu Subject: Mag North Vs True North To: ham-ant@ucsd.edu In article greg@netcom.com (Greg Bullough) writes: > >And of course the related, but equally puzzling question; if everyone >comes home at night and turns on their television at prime-time, does >the signal get weaker in fringe areas because of the number of receivers >which are now consuming more microvolts of signal close in? Well I can tell you what our transmitter engineer says. He says that the antenna current soars when our local news comes on because everyone out there is changing the channel to another station. Our SM overheard him telling the MC operator "She's gonna blow! The current's backing up and I can't handle it. You've gotta put on better programming." And the SM thought he was serious. He called the CE at home and asked him what we could do about the problem. You don't want to know what the CE said to the transmitter engineer. :-) Gary -- Gary Coffman KE4ZV | I kill you, | gatech!wa4mei!ke4zv!gary Destructive Testing Systems | You kill me, | uunet!rsiatl!ke4zv!gary 534 Shannon Way | We're the Manson Family | emory!kd4nc!ke4zv!gary Lawrenceville, GA 30244 | -sorry Barney | ------------------------------ Date: Thu, 9 Dec 1993 20:29:00 GMT From: pravda.sdsc.edu!usc!howland.reston.ans.net!agate!headwall.Stanford.EDU!Csli!paulf@network.ucsd.edu Subject: Mag North Vs True North To: ham-ant@ucsd.edu greg@netcom.com (Greg Bullough) writes: >And of course the related, but equally puzzling question; if everyone >comes home at night and turns on their television at prime-time, does >the signal get weaker in fringe areas because of the number of receivers >which are now consuming more microvolts of signal close in? My, what a helpful and informative posting. Yeah, right. To answer the original question, no, the magnetic polar offset does not "skew" signals; your aim should be based on true north. Now, there are some negative effects on paths which cross the polar region, owing to the concentration of flux lines; in particular, geomagnetic storms have a nasty effect on polar paths. -- -=Paul Flaherty, N9FZX | "Fighter pilots make movies. Bomber pilots make ->paulf@Stanford.EDU | history." -- Jake Grafton ------------------------------ Date: Fri, 10 Dec 1993 05:31:40 GMT From: sytex!jim@uunet.uu.net Subject: PI vs T Transmatch Circuits To: ham-ant@ucsd.edu Does anyone have any insight into building a switch into a transmatch so that it is switchable from PI to T? A friend of mine has a SWAN ST-1 antenna tuner that I am interested to buy. Only problem is that with my ridiculous indoor antenna situation (see below), I can't get it to load of 15 meters using the T circuit it comes built with. Works fine on 15 if I rewire it to a PI, but then it won't handle 80 meters. I'm considering putting a switch on the box and using it to switch between a PI and T configuration. Do THEY do that? Do I mess things up running the extra wires around in the box to make it possible? My antenna is an indoor 40/20 meter dual center fed dipole. (how it snakes around the wall is a lovely site for apartment dwellers to see). Loads great with the Little MFG $59 buck job. Since the MFJ isn't mine, but's on loan, I need to think about a replacement. Hence drolling over the SWAN, but I'll have to severly mod it. Opinions anyone? Jim -- AD4JE --- jim@sytex.com (Jim Arnold) Access <=> Internet BBS, a public access internet site Sytex Communications, Arlington VA, 1-703-528-4380 ------------------------------ Date: Wed, 8 Dec 1993 15:34:46 GMT From: olivea!sgigate.sgi.com!sgiblab!swrinde!cs.utexas.edu!howland.reston.ans.net!newsserver.jvnc.net!netnews.upenn.edu!netnews.noc.drexel.edu!dunx1.ocs.drexel.edu!dunx1!st92ba44@decwrl.dec.com Subject: short sw antennae? To: ham-ant@ucsd.edu hello there. (excuse any ignorance, please). I was wondering how I'd go about shortening my antanna electronically. I've noticed that most of the short ______________________________________ antonio gatta st92ba44@dunx1.ocs.drexel.edu ------------------------------ Date: Thu, 9 Dec 1993 21:29:33 GMT From: walter!att-out!cbnewsj!k2ph@uunet.uu.net Subject: T2FD antenna: any experiences? To: ham-ant@ucsd.edu ------------------------------ Date: Thu, 9 Dec 1993 21:32:19 GMT From: pravda.sdsc.edu!usc!math.ohio-state.edu!magnus.acs.ohio-state.edu!csn!col.hp.com!srgenprp!alanb@network.ucsd.edu Subject: T2FD antenna: any experiences? To: ham-ant@ucsd.edu Roger Traylor (rlt@ssd.intel.com) wrote: : In the book: PRACTICAL WIRE ANTENNAS : EFFECTIVE HF DESIGNS FOR THE RADIO AMATEUR : John D. Heys G3BDQ : Published by RSGB, 1991 : an antenna called "The Terminated Tilted Folded Dipole" (T2FD) is : described. It is a non-resonant, vertically polarized antenna with a : useful frequency ratio about 4:1. : 300 ohm : ______________________/\/\/\/\___________________ _ : | B C | : | | 1' 5" : |_______________________ ______________________| _ : A||D : || : || : 300 ohm twin lead You can always get better bandwidth by including lossy resistance, but you have the disadvantage that you are throwing power away. You would get about the same effect by using a resonant antenna and an attenuator. Better to buy an antenna tuner and tune a non-resonant, lossless antenna to the band in use. AL N1AL ------------------------------ Date: (null) From: (null) I tried this antenna a number of years ago. Dimensions were identical except for the 300 ohm terminating resistor. The article I had seen said to use 390 ohms for use with 300-ohm feed. I used a 6:1 balun from Palomar Engineers to bring it all down to 50 ohms. It had a really low SWR on 15 meters only. Around 1.3 to 1 across the band. Terrible SWR everywhere else. So, I compared it to a half-wave dipole on 40 meters at the same height. The dipole was typically about 2 S-units better than the T2FD. I also compared it on 20-15-10 meters to a TA-33 at the same height. The 3-element tribander was typically about 6 S-units better than the T2FD. I took down the T2FD and threw it in the garbage. 73, Bob K2PH -- ---------------------------------------------------- Bob Schreibmaier K2PH | UUCP: ...!att!mtdcr!bob AT&T Bell Laboratories | Internet: bob@mtdcr.att.com Middletown, N.J. 07748 | ICBM: 40o21'N, 74o8'W ------------------------------ End of Ham-Ant Digest V93 #140 ****************************** ******************************