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#11
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On Tue, 10 Oct 2006 21:30:24 -0500, Tom Ring
wrote: Richard Clark wrote: suggestion of a rhombic seems prohibitive in a neighborhood already far too sensitive to even a quarterwave vertical. is absurd on the face of it, would be absolutely unacceptable. Hi Tom, Again, a little judicous trimming reveals your complaint was already anticipated. 73's Richard Clark, KB7QHC |
#12
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Geoff Mendleson offered some good advice.
The dipole he suggested can be made using one 19-inch whip as the upper half of a vertical dipole and a 19-inch metal tube as the lower half of the dipole. The tube is also used as a sleeve over the coax which feeds the dipole at its center. This antenna is often called a coaxial or sleeve antenna. It is also often disguised to appear as something else such as a flagpole, etc. This antenna has 0 dBd gain and is omnidirectional in the horizontal plane. It works well in almost any line of sight direction and so is useful with portable and mobile stations. It is as good as a ground plane antenna without projections to cause injuries. Best regards, Richard Harrison, KB5WZI |
#13
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Richard Harrison wrote:
Geoff Mendleson offered some good advice. Thanks Richard. I appreciate the mention. The dipole he suggested can be made using one 19-inch whip as the upper half of a vertical dipole and a 19-inch metal tube as the lower half of the dipole. The tube is also used as a sleeve over the coax which feeds the dipole at its center. The advantage of using a whip and tube are the much wider bandwith than with a wire antenna. However if you are really stuck for places to put it, two 19" pieces of wire will do. Since most people only use a few watts on 2m FM, then the thinnest wire you can find will probably do. This antenna is often called a coaxial or sleeve antenna. It is also often disguised to appear as something else such as a flagpole, etc. This antenna has 0 dBd gain and is omnidirectional in the horizontal plane. It works well in almost any line of sight direction and so is useful with portable and mobile stations. It is as good as a ground plane antenna without projections to cause injuries. I think someone sells one that is a plastic pipe you slip over a vent pipe. If you are allowed TV antennas, you can build a "CIA special" which is a 2m and 440 beam fed by 300 ohm twinlead. On HF, the twinlead becomes the antenna and the beam part a capacative hat. I hid a J-Pole made of 300 ohm twinlead in side a white plastic pipe. If you use thin enough coax to feed it, it can be used to support all sorts of things, a pin-wheel or wind speed gage for example. 73, Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM IL Voice: (07)-7424-1667 Fax ONLY: 972-2-648-1443 U.S. Voice: 1-215-821-1838 Visit my 'blog at http://geoffstechno.livejournal.com/ |
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