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