Date: Fri, 3 Dec 93 04:30:20 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 #131 To: Ham-Ant Ham-Ant Digest Fri, 3 Dec 93 Volume 93 : Issue 131 Today's Topics: 2m car antenna? (2 msgs) 50 ohm coax to 75 ohm coax transformer Building a 2m/70cm mobile antenna First antenna for 160 meters helical antennas (2 msgs) LADDER LINE (2 msgs) Quad spreaders Setting up a HY-GAIN vertical Setting up a HY-GAIN vertical. 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, 30 Nov 1993 22:26:08 GMT From: bruce.cs.monash.edu.au!harbinger.cc.monash.edu.au!msuinfo!uwm.edu!vixen.cso.uiuc.edu!howland.reston.ans.net!newsserver.jvnc.net!netnews.upenn.edu!netnews.noc.drexel.edu!@@munnari.oz.au Subject: 2m car antenna? To: ham-ant@ucsd.edu Anyone have any recommendations for a trunk-mounted 2m or multi-band antenna? Basically I'm looking for someething similar to what I see some people doing with large cellular antennas, except for ham radio. Got a new Saturn, and I don't want to permanently mount anything or risk the paint scratches from a simple magmount antenna. :-) Bob -- Bob Snyder N2KGO MIME, RIPEM mail accepted snyderra@dunx1.ocs.drexel.edu finger for RIPEM public key ------------------------------ Date: Wed, 1 Dec 1993 12:53:14 GMT From: mdisea!mothost!lmpsbbs!news@uunet.uu.net Subject: 2m car antenna? To: ham-ant@ucsd.edu In article Fq9@Dunx1.OCS.Drexel.Edu, snyderra@dunx1.ocs.drexel.edu (Bob Snyder) writes: }Anyone have any recommendations for a trunk-mounted 2m or multi-band antenna? }Got a new Saturn, and I don't want to permanently mount anything or risk the }paint scratches from a simple magmount antenna. :-) } }Bob Bob, I use the corner of a "Zip Lock" freezer bag under my mag mount. I have had the vehicle painted once and that was the best looking spot on it! Be careful though, don't just use any type of plastic bag, alot will damage the paint, which is why I was specific in what I mentioned. Also, Don't be afraid of permanently mounting an antenna. Get one that has a common mount so when you go to sell, you can replace your 2m with a cellurlar antenna and now you have a feature! 73, Bruce, WB4YUC, el YUCCO. . . ------------------------------ Date: Wed, 1 Dec 1993 23:15:12 GMT From: world!dts@uunet.uu.net Subject: 50 ohm coax to 75 ohm coax transformer To: ham-ant@ucsd.edu In article tomb@lsid.hp.com (Tom Bruhns) writes: >Michael A Cecere (mac20@namaste.cc.columbia.edu) wrote: >: oh yeah, at 900MHz. would this be terribly complicated to homebrew? > >: I want to go from f-type connector 75-ohm "cable" coax to, get this, >: 9913 N-type coax. (the section of 75 ohm is just to match to the transceiver, >: the 9913 has to run over 100') > >An alternative to a 1/4 wave matching section of impedance sqrt(75*50) >is given in the RSGB VHF/UHF book. It uses only pieces of the two >lines you wish to match. Pardon the crude diagram: > > > Line1----===line2===---Line1---========line2 > >where the lengths of the intermediate lines are equal, and for the >75 ohm to 50 ohm case would be, as I recall, 0.081 wavelengths >long (accounting for the propagation velocity in the cable). See >the RSGB book for the formula, and to check on my memory about >the 0.081. Kinda nice to know you can do the transformation >without building a section of some intermediate impedance, but >at 900MHz, these sections are rather short, and you would want >to be really careful about lengths and assembly techniques. Probably >easier to use at 2 meters and lower frequency. > I think the original poster is interested in working with WaveLAN. If this is the case, and the usage will be for non-amateur use, you might want to call up Joe Reisert (W1JR) at Antennaco (Amherst, NH, I think, but if you need the info, I have it at home). Joe has antennas and other supplies needed to do Wavelan installations (including yagis set up for 75 ohm). From what he told me, the system is limited by the FCC in terms of ERP, not output power, so it may not be necessary to go too far overboard on coax and such. Of course if the application wasn't WaveLan, please ignore the above! -- --------------------------------------------------------------- Daniel Senie Internet: dts@world.std.com Daniel Senie Consulting n1jeb@world.std.com 508-365-5352 Compuserve: 74176,1347 ------------------------------ Date: 2 Dec 1993 04:10:15 GMT From: concert!samba.oit.unc.edu!not-for-mail@decwrl.dec.com Subject: Building a 2m/70cm mobile antenna To: ham-ant@ucsd.edu Greetings: I'm kinda new to Ham Radio and am usually broke as well. Does anyone have any ideas or plans to build a *cheap* dual band antenna for 2m/70cm to mount on a truck bumper? I'm using a Yeasu FT-727 and will probably be building the 2m amplifier in the Nov. issue of 73 magazine. Any comments, suggestions, warnings, plans, diagrams, etc... will be appreciated. Responses may be e-mailed to: a10rxw1@hayek.cob.niu.edu 73 de KF9QQ -Rich- -- The opinions expressed are not necessarily those of the University of North Carolina at Chapel Hill, the Campus Office for Information Technology, or the Experimental Bulletin Board Service. internet: laUNChpad.unc.edu or 152.2.22.80 ------------------------------ Date: 2 Dec 93 19:15:28 GMT From: idacrd.ccr-p.ida.org!idacrd!n4hy@uunet.uu.net Subject: First antenna for 160 meters To: ham-ant@ucsd.edu I am a 160 meter operator at N2RM and that is a site that uses inverted L's. They perform brilliantly and have a nice low angle of radiation. You do definitely want the performance enchancement you will get from the vertical portion for the skywave coming in on 160. HOWEVER, the antenna will be CRAP if you cannot lay out a bundle, and I do mean a bundle of radials. If you do not have room for quarter wave radials, 30-50 of them, go with the inverted vee. Bob -- Robert W. McGwier | n4hy@ccr-p.ida.org Interests: ham radio, Center for Communications Research | scouts, astronomy,and golf Princeton, N.J. 08520 | ASM Troop 5700, ACM Pack 53 Hightstown (609)-279-6240(v) (609)-924-3061(f)| I used to be a Buffalo . . . NE III-120 ------------------------------ Date: 2 Dec 93 19:46:34 GMT From: ogicse!uwm.edu!math.ohio-state.edu!sdd.hp.com!col.hp.com!srgenprp!glenne@network.ucsd.edu Subject: helical antennas To: ham-ant@ucsd.edu peake@dstos3.dsto.gov.au (peake@dstos3.dsto.gov.au) wrote: : The antenna design book by Jasik gives a design for four helices with : alternating lh/rh polarities. Matching is achieved by noting that the : feed point impedance of a single helix (as described in the text) is : about 140 ohms. A tapered line segment of 140 to 200 ohms couples each : helix to a centre point where 4@200 ohms in parallel gives 50 ohms. : Imade one of these to work at 1800 MHz (non-amateur) but was disappointed : with the results. The gain was < 7dB. Analysis with a TDR showed that the : impedance matching seemed to be ok apart from a low impedance dip at about : the point where the helix feeds through the reflector plate. This is : only about 3mm thick so I don't see how that could make such a big : difference. I would be glad of any ideas about this. I've never combined four helices that way but I have used a tapered line to get from 140 ohms to 50 on a single helix. The result was very satisfactory over a fairly large bandwidth. I don't remember the particulars but it was certainly fine on the ham bands. I think I did it for both 1240-1300 and 420-450. In the past I've just extended the conductor used for the helix, 1/4" aluminum gas line in one case, and tapered it's distance from the backside of the reflector to create the tapered quarter wave section for matching. Using a TDR can be a little tricky since it may reveal information about performance considerably beyond the range of expectations. Using a network analyzer with band limited sweep in frequency domain followed by the conversion to time domain might be safer. I wouldn't expect the small discontinuity going through the reflector to have a lot of impact on inband performance either. Glenn Elmore n6gn ax.25 n6gn@wx3k.#nocal.ca.usa.na amateur IP: glenn@SantaRosa.ampr.org Internet: glenne@sr.hp.com ------------------------------ Date: 3 Dec 93 00:36:32 GMT From: ogicse!hp-cv!sdd.hp.com!col.hp.com!srgenprp!glenne@network.ucsd.edu Subject: helical antennas To: ham-ant@ucsd.edu Richard Karlquist (rkarlqu@scd.hp.com) wrote: : In article , Joe Mack wrote: : >I've talked about making linear polarized beams from two helices with another : >ham and we've both reached the same and rather discomforting conclusion : >that the power that is in the direction which is not radiated in the forward : >direction is instead radiated in weird side lobes. The thinking goes like this- : Your reasoning would be correct at sufficiently large : spacings, but for reasonable spacings, by the time the : angle gets large enough to make the vertical beams add : instead of cancel, the gain of the vertical beams should : be less than a dipole. So the combination of the two will I also think this is correct. If only forward gain is considered, antenna spacing wants to be large enough so that the individual antennas don't share each other's aperture; the power can only be "caught" once and all the best of antennas can do is perfectly capture all power hitting its aperture. However, at very wide spacings the angle at which the sidelobes start to get bad decreases. This means that short antennas don't want to be separated a large amount. There have been some rules-of-thumb to address this. One old one (I'm not saying it is correct) is to space yagis by a boomlength. I believe there are some papers which address this issue. I vaguely remember that there is one by Silver which talks about what the first sidelobe level should be for some optimum gain/pattern circumstance. Something on the order of -12 dB is what I remember but I don't know how it is to be interperted. : to say radar) it is not a big deal. [Disclaimer: I've : never built this antenna, so this is just my opinion of : the theory] : Rick N6RK And I've never measured stacked counter-polarized helices either. However, I would think that a similar argument could be applied to stacked anything. At some angle things add the "wrong" way. You just want to be sure that the resulting vector isn't big enough to be a problem at any angle of interest. Glenn Elmore n6gn ax.25 n6gn@wx3k.#nocal.ca.usa.na amateur IP: glenn@SantaRosa.ampr.org Internet: glenne@sr.hp.com ------------------------------ Date: 1 Dec 1993 16:45:43 GMT From: organpipe.uug.arizona.edu!helium!hlester@uunet.uu.net Subject: LADDER LINE To: ham-ant@ucsd.edu In article <01H5YMHPZUIG8Y62MD@wl.aecl.ca>, wrote: > >I'm feeding a G5RV with 300 Ohm twin lead (low loss foam dielectric from >RS )directly from a tuner. I am wondering whether I would be further >ahead using 450 Ohm ladder line. I am concerned about the wire-to-wire My understanding is that you should NOT use twinlead with a FOAM dielectric. For that reason alone, 450 ladder line is much preferred. Since you're planning on running as much as 500w peak, even regular tv twinlead may be insufficient. Howard ------------------------------ Date: 1 Dec 1993 08:52:45 -0800 From: ucsnews!sol.ctr.columbia.edu!howland.reston.ans.net!cs.utexas.edu!asuvax!chnews!ornews.intel.com!ornews.intel.com!not-for-mail@network.ucsd.edu Subject: LADDER LINE To: ham-ant@ucsd.edu In article <01H5YMHPZUIG8Y62MD@wl.aecl.ca> MCILWAINA@wl.aecl.CA writes: > >I'm feeding a G5RV with 300 Ohm twin lead (low loss foam dielectric from >RS )directly from a tuner. I am wondering whether I would be further >ahead using 450 Ohm ladder line.... My limited experience with 300 ohm twin lead is that it changes characteristics drastically when its wet. I can tell this by changes in the tuning on my Matchbox as well as some trouble getting a match when its wet. The 450 ohm stuff seems much better in this respect. -- zardoz@ornews.intel.com WA7LDV ------------------------------ Date: 2 Dec 93 03:29:55 GMT From: ogicse!uwm.edu!spool.mu.edu!sdd.hp.com!nobody@network.ucsd.edu Subject: Quad spreaders To: ham-ant@ucsd.edu I'm trying to hack together a quick 3-el 10 meter quad for next weekend. What's the theory on quad spreaders? Must they be non-metallic? Does anyone have a decent source for fiberglass spreaders? I was going to use bamboo, but I can't find any locally. (Except for live bamboo plants!) Thanks. -- Holt Mebane, N4HR Hewlett-Packard San Diego Technical Graphics Division 619-592-4882 ------------------------------ Date: 3 Dec 93 11:32:49 GMT From: news-mail-gateway@ucsd.edu Subject: Setting up a HY-GAIN vertical To: ham-ant@ucsd.edu Thanks to the folks who were kind enough to help. In case there is someone else with a similar question: HY-GAIN is a part of Telex. I just asked for technical support, and they promised to send me the relevant papers. Very classy. Jim KB2HEO Jim Hefferon Math, St.~Michael's College, Colchester VT, USA 05439 internet: hefferon@smcvax.smcvt.edu (802) 654-2677 ------------------------------ Date: 2 Dec 93 14:26:00 GMT From: news-mail-gateway@ucsd.edu Subject: Setting up a HY-GAIN vertical. To: ham-ant@ucsd.edu Hello, I'm a Novice. I got an antenna as part of a package (along with a tranciever, etc.) that has no documentation. I was wondering if some kind soul could give me some hints as to how to proceed. I'm specifically worried about length to which the sections should be telescoped, but I'm grateful for any pointers. Here is a picture: (I apologize if this is too much /\ data, but perhaps too much is better | | than too little?) ------ | | <-- label: 15M ASSY 878417 I tried telephone information | | LINCOLN NEBR. U.S.A. in Lincoln, but they said ------ 57010 HY-GAIN 1989 HY-GAIN has not been listed | | for a long time, and QST ------ has no ads from them. | | <-- label: 10M ASSY 877132 | | LINCOLN NEBR. U.S.A. ------ 57010 HY-GAIN 1989 | | ------ Does anyone know if I could | | reach HY-GAIN? I thought they | | might be able to send some | o | <--screw papers. |----|- | | | <-- mounting bracket | | | ------- ^ <-- female UHF Thanks, Jim KB2HEO. Jim Hefferon Math, St.~Michael's College, Colchester VT, USA 05439 internet: hefferon@smcvax.smcvt.edu (802) 654-2677 ------------------------------ End of Ham-Ant Digest V93 #131 ****************************** ******************************