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Scanner antenna ???
Tom wrote:
Hi I have the Realistic Programmable scanner with 200 programable channels. A lot of range there like 6 m, 2 m, 70 cm, marine, etc etc etc, wide range. I want to put up an external antenna that I can hook it up to its own BNC connection for external antenna. I believe the higher the better. Which is better to run a bare copper wire longest and highest to connect it to the BNC center? Or should I use coax and splice the center copper feed to a certain length from its shield and just get that piece of the antenna the highest possible? Would it make better receive sense to simply use one leg of the 16ga copper wire with jacket that I have and use for dipoles? If I use an adapter (SO239 x BNC) and hook the scanner up to my Alpha Delta DX-CC which has a lot of exposed copper very high and very long and available, Is that a better receive antenna than would be another piece of coax spliced at a certain length and get that up there higher? Simply for scanner of course, nothing transmit, Appreciate any comments on this, cheap or otherwise, For VHF use it is not a good idea to connect a very long bare wire to the antenna connector, because only a short part of the wire close to the receiver will be active and thus you have an indoor antenna even when the wire runs outside. As you write, the higher the better. So it is better to run a decent quality coax to outside and construct a simple antenna connected to the end of it. Generally, the thicker the coax the better, but no need to over-spend on this. For receive only, a random length (in the ballpark of 1/2 wavelength) vertical dipole is good enough. You can make it a true dipole or you can use some "groundplane" configuration (one quarter wavelength pointing upward and connected to the coax center, and three or four quarter wavelength rods slanting downward and connected to the braid). The latter may be more convenient when you want to put it on top of a short pole. Indeed, you can also just strip the end of the coax and fold back the braid over the end of the coax to form a halfwave dipole, and put the whole thing in a plastic tube. When looking inside commercially available scanner antennas, you will often find just a copper wire inside the plastic stick. Often there has been an attempt to make it more wideband by winding it in the form of a couple of coils (3 turns or so) every 10 inch or so, but if that really makes any difference in the results is to be seen. |
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