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21. Re: Topband: Shunt fed tower (score: 1): Author: Herb Schoenbohm <herbs@surfvi.com>; Date: Sun, 25 Apr 2010 09:19:19 -0400; Normally the "sweet point" where the connection between the gamma rod and the tower will exhibit 50 ohms plus some inductive reactance makes the gamma rod easier to match, i.e. less components in the; /archives//html/Topband/2010-04/msg00088.html (10,083 bytes)
22. Topband: Shunt fed tower (score: 1): Author: "John Harden, D.M.D." <jhdmd@bellsouth.net>; Date: Sun, 3 Oct 2010 11:46:06 -0400; Interesting to see all of the comments about feeding a vertical antenna.... I use a 100 foot 45G tower with a shunt feed for top band. Because the tower is festooned with rotary antennas for 80 - 1-0; /archives//html/Topband/2010-10/msg00016.html (6,961 bytes)
23. Re: Topband: shunt fed tower (score: 1): Author: DM4iM <hamradio@vr-web.de>; Date: Sat, 22 Jan 2011 23:42:10 +0100; Topbanders, thanks to all who responded. Special thanks to Greg, ZL3iX, for the pictures. I connected the parasitic elements per his hints and the SO-239 plug at the radiator housing to the boom. The; /archives//html/Topband/2011-01/msg00119.html (7,228 bytes)
24. Topband: Shunt fed tower (score: 1): Author: John Harden <jhdmd@bellsouth.net>; Date: Thu, 15 Dec 2011 06:51:12 -0500; I've been reading all of the posts about the 160 shunt feeds... I have a 100 foot 45G tower festooned with monobanders from 80 - 10 meters. Because of the monobanders my 4-wire cage is only 30 feet h; /archives//html/Topband/2011-12/msg00353.html (6,935 bytes)
25. Re: Topband: Shunt fed tower (score: 1): Author: W2RU - Bud Hippisley <W2RU@frontiernet.net>; Date: Thu, 15 Dec 2011 07:27:40 -0500; Many shunt-fed, loaded towers on 160 exhibit narrow bandwidth and are difficult to match with a single series capacitor for one simple reason: The gamma rod (shunt wire) is TOO CLOSE to the tower. A; /archives//html/Topband/2011-12/msg00354.html (8,988 bytes)
26. Re: Topband: Shunt fed tower (score: 1): Author: "Joe Subich, W4TV" <lists@subich.com>; Date: Thu, 15 Dec 2011 10:17:35 -0500; That is true but a 100 foot tower with decent sized 20M monobander or 24 foot boom tribander with the front/back elements grounded and a short 40 meter yagi will most certainly have a natural resonan; /archives//html/Topband/2011-12/msg00362.html (11,547 bytes)
27. Re: Topband: Shunt fed tower (score: 1): Author: W2XJ <w2xj@nyc.rr.com>; Date: Thu, 15 Dec 2011 10:34:32 -0500; Vertical antennas have been shunt fed for over 70 years. There is no magic involved. Very few MW verticals are ever resonant and resonance is irrelevant. The only important thing is to match the TX s; /archives//html/Topband/2011-12/msg00365.html (12,933 bytes)
28. Re: Topband: Shunt fed tower (score: 1): Author: "Joe Subich, W4TV" <lists@subich.com>; Date: Thu, 15 Dec 2011 10:59:32 -0500; All true but one does not want a tower that is "too tall" that the pattern deteriorates. The shunt is *not* connected to the 50 Ohm point. It is connected to the point that is *transformed to 50 Ohms; /archives//html/Topband/2011-12/msg00370.html (14,763 bytes)
29. Re: Topband: Shunt fed tower (score: 1): Author: Bob K6UJ <k6uj@pacbell.net>; Date: Thu, 15 Dec 2011 08:05:00 -0800; Joe, W4TV, Thanks for the info on the insulators. ! I just ordered some myself. These are great for making a fat gamma rod as you indicated. (They are a little pricey though, a whopping 35 cents apie; /archives//html/Topband/2011-12/msg00371.html (13,204 bytes)
30. Re: Topband: Shunt fed tower (score: 1): Author: "ZR" <zr@jeremy.mv.com>; Date: Thu, 15 Dec 2011 08:37:24 -0500; At a prior QTH I had a 90' Rohn 25 with 16' of mast above and stacked 4el W2PV design yagis. The 1/4 wave resonance was 1585 KHz if I remember and the 1" CATV hardline used for a gamma was space 3'.; /archives//html/Topband/2011-12/msg00376.html (10,958 bytes)
31. Re: Topband: Shunt fed tower (score: 1): Author: W2XJ <w2xj@nyc.rr.com>; Date: Thu, 15 Dec 2011 12:08:05 -0500; Agreed, my bad semantics. That said I was thinking more of a sloping shunt similar to was was used in broadcast. I don't think many will have a "too tall" problem on 160 M unless some lucky person ha; /archives//html/Topband/2011-12/msg00378.html (16,080 bytes)
32. Re: Topband: Shunt fed tower (score: 1): Author: "Price Smith" <w0rihps@sbcglobal.net>; Date: Thu, 15 Dec 2011 12:17:13 -0600; Construction: My local ACE hardware store stocks 8-foot lengths of angle aluminum, which is what I used for my horizontal tap rod. Their heaviest-duty stock is more than strong enough to support itse; /archives//html/Topband/2011-12/msg00385.html (10,580 bytes)
33. Re: Topband: Shunt fed tower (score: 1): Author: "Peter Voelpel" <df3kv@t-online.de>; Date: Thu, 15 Dec 2011 19:32:20 +0100; I direct feed my tower against a sloping radial which works extremely well for me. The highest antenna is at 45m and further down are more monobanders, most side mounted. I do not need any capacitor; /archives//html/Topband/2011-12/msg00386.html (10,852 bytes)
34. Re: Topband: Shunt fed tower (score: 1): Author: "Larry" <lknain@nc.rr.com>; Date: Thu, 15 Dec 2011 16:14:26 -0500; I haven't done much modeling in the past.I have a KT36XA which would be very ugly if I had to model it precisely. I also have a linearly loaded 2 el 40M yagi. I suspect that the loading wires probabl; /archives//html/Topband/2011-12/msg00396.html (14,685 bytes)
35. Re: Topband: Shunt fed tower (score: 1): Author: W2XJ <w2xj@nyc.rr.com>; Date: Thu, 15 Dec 2011 16:28:59 -0500; For most of us a precise model is not possible. EZNEC will give you an approximation. The tower is represented as a cylinder equal to the cross section of the real tower. You could measure the existi; /archives//html/Topband/2011-12/msg00397.html (16,015 bytes)
36. Re: Topband: Shunt fed tower (score: 1): Author: "Larry" <lknain@nc.rr.com>; Date: Thu, 15 Dec 2011 16:37:19 -0500; The tower as a cylinder, 50 ohms at the feed point, etc I knew. Dealing with the yagis was not so clear but your procedure seems like a reasonable and do-able method to deal with it. Thanks For most; /archives//html/Topband/2011-12/msg00398.html (16,711 bytes)
37. Re: Topband: Shunt fed tower (score: 1): Author: Herb Schoenbohm <herbs@vitelcom.net>; Date: Thu, 15 Dec 2011 18:49:58 -0400; Larry, Because of the complexity of modeling without going crazy, although in simple situations it will get you in the ball park, I would highly recommend a 3 or 4 wire cage space at least 24 inches; /archives//html/Topband/2011-12/msg00404.html (11,980 bytes)
38. Re: Topband: Shunt fed tower (score: 1): Author: "ZR" <zr@jeremy.mv.com>; Date: Thu, 15 Dec 2011 16:38:55 -0500; Hang a bare wire top to bottom and 2-3' from the tower. Have one person on the tower with a clip lead and another at the base with an analyzer and a couple of variable caps. Move the clip lead one ru; /archives//html/Topband/2011-12/msg00407.html (15,926 bytes)
39. Re: Topband: Shunt fed tower (score: 1): Author: "Larry" <lknain@nc.rr.com>; Date: Thu, 15 Dec 2011 18:45:37 -0500; Herb, I tried measuring the tower resonance with a GDO as suggested by ON4UN's book but my GDO wouldn't go low enough in frequency to find resonance. It appears to be below 1.5MHz (100 ft 45G with a; /archives//html/Topband/2011-12/msg00410.html (14,318 bytes)
40. Re: Topband: Shunt fed tower (score: 1): Author: W2XJ <w2xj@nyc.rr.com>; Date: Thu, 15 Dec 2011 18:59:49 -0500; I would ditch the GDO and measure R and J. _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK; /archives//html/Topband/2011-12/msg00411.html (15,423 bytes)

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