Originally Posted by
Al Burgemeister
Ian, the challenge I think you may have is that all those cross members (if they are conductors) and cables is that they form a distributed, but messy, ground plane, whether you want them or not. Running one leg of your dipole down among this "mess" will affect the performance of your antenna, both the loading that affects how much power gets out and the antenna pattern.
Jim Weir may have some other suggestions but in my opinion you might want to consider constructing a ground plane for a 1/4-wave antenna in your turtle deck and take the drag hit of an exposed antenna. Also, you mentioned constructing the antenna of piano wire. The bandwidth (tuning range) of an antenna is affected by the diameter of the radiating element. A piano wire antenna will work well at one frequency and less well if you tune to other frequencies in the VHF aircraft band.