Date: Mon, 18 Jul 94 04:30:22 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 #227 To: Ham-Ant Ham-Ant Digest Mon, 18 Jul 94 Volume 94 : Issue 227 Today's Topics: 80m Compact Loop--help DDRR antenna for Radio Astronomy J-pole Antenna On glass 2M & 70cm advice SWL antenna suggestions Twin Lead Jpole? Who invented the T2FD ? 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: 17 Jul 1994 22:34:25 -0400 From: agate!howland.reston.ans.net!news.intercon.com!news1.digex.net!digex.net!not-for-mail@ames.arpa Subject: 80m Compact Loop--help To: ham-ant@ucsd.edu In article , Theodore J. Bittner wrote: > I live in a restricted subdivision, and I read with > interest the article by Jim McLleland, WA6QBU; "Roll Your Own > Compact 80 Meter Wire Loop Antenna", CQ,July 94, pp 44-46. > The article states the "twist" in the loop is what > gives the antenna so much distributed capacitance to allow it > to work on the low bands, but in the construstion tips no > mention is made of physically putting a twist in the loop. > In point 7 of the construction tips Jim says to locate > wires at opposite ends of the loop that do NOT connect to each > other for the lead ins and use the other set to connect to the > capacitance stub. I'm assuming this is what creates the twist > in the loop, correct? > I feel dumb for asking, but I've learned not to assume > anything. Any thoughts to set me straight would be most > appreciated, as this design might help me out on 80m. > Thanks in advance for the advice. > > Ted--KQ4MZ > Charlottesville, Va Ted, Yes, 'twisting' the 300 ohm line 180 degrees is what is required. I built his 40M version last October (Sept 73 Magazine) and have had absolutely great results. It is within 2 s-units of a full size inverted vee. I placed the loop in my attic and use the tuner the way he recommends. I suggest that you spread the ends of the tuning stub and ALL connect point at least 2 inches (I use pc bread board material) otherwise you'll get a nasty arc if you exceed 50 watts. The arc burns the 300 ohm insulation and the SWR goes crazy from the carbon build up (yep, happened to me). Good luck and let me know how you make out. Heck, lets try to work each other w/the loops, that'll be a good test. I'll have my 80M version in the attic in a few weeks (as soon as I have a cool night to get into the attic). 73... Andy N3LCW ------------------------------ Date: Sun, 17 Jul 1994 16:37:51 GMT From: ihnp4.ucsd.edu!dog.ee.lbl.gov!newshub.nosc.mil!news!aburto@network.ucsd.edu Subject: DDRR antenna for Radio Astronomy To: ham-ant@ucsd.edu ------- Hello, I have an interest in observing radio emissions from Jupiter. An antenna hardware design (DDRR type antenna), using PVC pipe, soft copper tubing, and wire mesh for a ground plane, was given in a special issue (1994-3) of Radio Astronomy, The Journal of the Society of Amateur Radio Astronomy (SARA). Only trouble is that the DDRR antenna was designed for 21.6 MHz, which is too low for my reciever (IC R7100, 25 MHz to 2 GHz). I'd like to redesign the antenna for 25.200 MHz (This seems to be a quiet frequency for listening --- I hope). Any one have the relevent equations handy? The SARA article used a design by F. W. Hyde in 'Radio Astronomy Techniques', Practical Electronics, Mar 1992, Pg 221. I don't have this reference. Paul Harden (pharden@zia.aoc.nrao.edu) told me to use a copper tubing length of L = 468 / F (feet), where F is the frequency in MHz, for Lambda over 2 or one half that for Lambda over 4. This is what I'm doing now but it would be good if I could learn how to derive the equations myself or find a good reference for this type antenna. I bought The ARRL Antenna Book, but the DDRR there seems to be different from that described by F.W. Hyde. Al Aburto aburto@marlin.nosc.mil ------- ------------------------------ Date: 17 Jul 1994 22:52:34 -0400 From: elroy.jpl.nasa.gov!usc!howland.reston.ans.net!newsserver.jvnc.net!yale.edu!noc.near.net!shore.shore.net!northshore.ecosoft.com!not-for-mail@ames.arpa Subject: J-pole Antenna To: ham-ant@ucsd.edu I recently bought a Kenwood TS-430. I am looking for some information on building a J-pole antenna that will run from 80m-10m. Not to worried about the 160m band yet. I have checked a couple of sources, but have had no luck. Any Comments? Thanks, Jeff Stutzman (N1LUY) ------------------------------ Date: Sun, 17 Jul 1994 17:07:48 GMT From: spsgate!mogate!newsgate!jump!lynch@uunet.uu.net Subject: On glass 2M & 70cm advice To: ham-ant@ucsd.edu I want to put a dual band (2M / 70cm) on glass antenna on my Ford Explorer. I have a height restriction because of my garage and want to try and keep the entire length of the antenna to 25 inches or less. So far I have not been haveing very much luck. I have found the Larsen KG 2/70 but its overall length is about 31 inches. I have seen another one from Mobile Mark advertised but have not been able to find one at HRO or other outlets. The Mobile Mark is evidently 24 inches in length. Has anyone heard any reports about the Mobile Marks performance? Does it need to be connected to the car for a ground.? Any other suggestions for a dual band on glass antenna between 12 and 25 inches? Scott Lynch KC7ADV lynch@chdasic.sps.mot.com ------------------------------ Date: 18 Jul 1994 01:08:40 GMT From: koriel!news2me.EBay.Sun.COM!jethro.Corp.Sun.COM!seurat!markl@ames.arpa Subject: SWL antenna suggestions To: ham-ant@ucsd.edu I'm new to SWL and looking for suggestions for antenna designs. The area I have to work with is 15-20 ft. square horizontally, 4-5 ft vertically. As a start I put 50ft of long wire in a horizontal V facing SW (the longest, almost-straight configuration I could make). Is a directional antenna called for when power lines are nearby? I'm on the west coast with lots of exposure from S through W to N, but with hills, houses, and powerlines right behind me. Also, what kind of simple filters can I make to reduce noise? Thanks! Mark markl@corp.sun.com ------------------------------ Date: Sun, 17 Jul 1994 16:31:55 GMT From: lll-winken.llnl.gov!overload.lbl.gov!agate!library.ucla.edu!csulb.edu!csus.edu!netcom.com!netcom10!faunt@ames.arpa Subject: Twin Lead Jpole? To: ham-ant@ucsd.edu I thought I had the instructions for this stored somewhere, but it must be on the computer that's down. Could someone send them to me? thanks, and 73, doug ------------------------------ Date: Sun, 17 Jul 1994 18:24:35 GMT From: ihnp4.ucsd.edu!sdd.hp.com!spool.mu.edu!howland.reston.ans.net!europa.eng.gtefsd.com!uhog.mit.edu!news.kei.com!ub!freenet.buffalo.edu!aa450@network.ucsd.edu Subject: Who invented the T2FD ? To: ham-ant@ucsd.edu In a previous article, charlos@rivm.nl (Charlos Potma) says: >I am writing an article for our local club newsletter about the >Tilted Terminated Folded Dipole (T2FD). I have read a few articles >on the subject, particularly the ones in QST of june '49 and november >'51 written by W3HH. However it is not clear from these articles who >the actual inventor of the T2FD was and what the intended application >would have been. I would like to hear from anyone having more information >on this subject, > > >^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > Charlos Potma PA3CKR (charlos@rivm.nl) >RIVM - National Institute of Public Health and Environmental Protection > Laboratory for Air Research > Postbox 1, 3720 BA BILTHOVEN, the Netherlands > tel. ++31 30 743831, fax. ++31 30 287531 >^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > Carlos, John Heys, G3BDQ, in his book discusses the T2FD and says, "...developed in the late forties by Capt. G.L.Countryman, USN, W3HH, ...". He goes on to say that the antenna was used at the Long Beach Naval Station, California successfully and that it's radiation pattern and field strength measurements there were superior to a Marconi antenna. Hope this helps, email if there are any details you wish. 73, Kurt, N2TTE -- ------------------------------ End of Ham-Ant Digest V94 #227 ******************************