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On 4/21/2012 7:09 PM, christofire wrote:
"Jeff wrote in message ... For some irrational reason, that probably defies logical justification, I've decided to setup my PCR1000 receiver as an internet accessible receiver. There are about 7 programs available to do this, so I don't expect software to be a problem. The receiver will eventually be moved to a mountain top repeater site, which unfortunately does not have much room for an antenna. The receiver will tune from 0.1 to 1300Mhz. I don't wanna deal with an antenna tuners or switches. Is there an antenna or combination of antennas that are suitable for such a wide tuning range and that is small enough to fit in a limited rooftop area? I was thinking of a monstrous vertical biconical dipole for HF, a diplexer, and a discone for VHF/UHF/etc. For Field Day, I once made a biconical out of two trash can lids, with holes for the wires around the perimeter. It worked amazingly well but I never bothered to make measurements. http://en.wikipedia.org/wiki/Biconical_antenna Can anyone suggest something better, smaller, less ugly, or more practical? -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 If it's always receiving and you can make an amplifier with high input impedance throughout the frequency range, then you could use a short dipole 'doublet' - drawing insignificant current from the antenna would make its very low radiation resistance less of a concern. Its directivity gain would be almost constant because its radiation pattern comes from its (fixed) axial symmetry, but a wavelength^2 factor would apply to its effective aperture area. It probably wouldn't be easy to design a single high-input-Z amplifier over that frequency range, but there might be scope for dividing the range and combining the _outputs_ of several amplifiers, each fed by their own doublet. Would you need any kind of 'monstrous' antenna if the requirement was always receiving? I could see that you might want something large to get the radiation resistance up if you were transmitting from it, but for receiving a high-Z amplifier becomes easier at lower frequencies. I vaguely recall that some of the companies that have offered professional 'radiomonitoring' (i.e. evesdropping) equipment, such as R&S, have used combinations of different types of element for different parts of the wide frequency band, but never anything monstrous. Chris The only comment I would have is capture area. tom K0TAR |
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