Not necessarily. I use this antenna with excellent results.

http://advancedaircraft.com/index.htm

Aircraft Spruce carries them. No ground plane needed.

Bob

Fred wrote:
Robert:

Why not just "installed such-and-such xpdr IAW manufacturer's
installation manual?" Your problem is going to be the antenna, though,
isn't it? You probably need to put an aluminum bulkhead from side to
side inside boom to make a ground plane. LaSor