steve2004 said:
"40 MHz spread at VHF"
I Don't get that one...
I don't a wideband just to cover airplane & 154.xxxx (cops)
simple to build
Don't worry with the J-Pole... make a 1/4 wave ground plane.
Get you 5 pieces of aluminum or 12gauge solid copper wire, an SO-239 connecter, and 4 bolts and nuts. You'll want to cut 4 of the wires to about 23" long and one at 19" long. The 19" long piece will be the vertical radiator which will be soldered into place on the SO-239. Then the 4 23" pieces will be bolted into the 4 mounting holes of the SO-239. You'll want to bend the 4 wires (ground radials) into a 45 degree angle from the point where they are mounted.
The 45 degree angle will allow the feedline (coax) and the antenna maintain a 50ohm impedance. The longer the radials the lower the frequency it will be tuned for. That range I listed would put you right about the 140-150 mhz range which is a good middle ground to be in if you want to listen to 118-137 and 154-160 mhz.
Then once you have the radials attached to the SO-239 you'll want to find a way to mount it to a pole, usually a piece of plastic or something non-conductive.