On Sat, 4 May 2013 15:48:22 -0400, "Tom" wrote:

Yes, I have the tower and have a bracket that extends to the side about 4 ft
and this antenna will be at the end of that extension.

Perfect, but not for the obvious reason. Retail discone antennas cost
$25 to $150, which seems a bit high. Mostly, it's because of the
large number of parts involved. If you have a tower and yard-arm, you
can hang a center fed vertical biconical antenna off the end, which in
my never humble opinion will work better than a discone (due to the
reduced up tilt of the vertical radiation pattern) than a discone.
Discones are good for broadband, and listening to airplanes, but if
you want distance, the radiation pattern should point to the horizon,
not the sky. Something like one of these:
https://www.google.com/search?q=biconical+antenna&tbm=isch

Realistic 2037.

http://www.rigpix.com/rs-realistic/realistic_pro2037.htm
Made by GRE starting in about 1996. It has a marginal front end
design that is easily overloaded by strong signals and will produce
intermod mixes with little effort. The "ATT" for attenuation switch
is an obvious clue. If you hear obvious intermod, you may want to
insert a 1/4 wave stub notch filter between the antenna and receiver
to get rid of strong paging junk and such.
http://dl4xav.sysve.de/coax.filter/coax-filter.html

The more strange looking and ugly the antenna, the better it works.

I see a lot of them have ground planes or are all those elements part of the
center wire in the bnc?

The bottom angled elements are at ground potential. The flat top
"hat' is connected to the center wire of the UHF connector. If you
replace the flat top hat, with a mirror image of the ground elements,
you have an instant biconical antenna.

I have an old 2m 70cm diamond antenna with gnd planes, Suppose that would
work also? But someone gave it to me because it didn't work so might take a
closer look at it.

A dual band antenna will work on 2m and 70cm, and little else. You
can probably hear something on the adjacent frequencies, but at more
than a few MHz away, such an antenna is going to be comatose. If you
use your scanner mostly for these ham bands, put a ground plane under
it, as if it were mounted on a vehicle, and attach it to your
yard-arm. If that's too messy, several 1/4 wave at 2m horizontal
ground radials will probably suffice.

Incidentally, don't toss the antenna. Diamond make good antennas and
it's probably worth your time to determining why it didn't work.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558