I recently picked up a Diamond f22a 2 meter antenna. I would like to tune it
to the aircraft band (123mhz). I have a couple of questions: How much length
would I need to add to it? It looks like I can add about 8-10" inside the
top fiberglass tube. Is it worth the trouble? Will it improve reception.
I've done google searches and even talked to Diamond and can't come up with
a figure. Any help would be greatly appreciated.

Joe