Aircraft antennas

Jim Carriere wrote:

Please excuse my "piggybacking" your question, can anyone with an
informed opinion weigh-in on this:

http://www.aircraftspruce.com/catalo...nnasystems.php

You put it inside a tube and fabric structure. Seems like a good idea
at first glance...

VHF COM, NAV, and ELT antennas placed inside a welded-tube fuselage
aren't worth crap!
What is the biggest complaint of anybody trying to use a Air-band VHF
hand-held transceiver inside the cabin of a metal aircraft? They cant
be heard! They all end up putting an external antenna on their
aircraft. And no, it is not just the inefficiency of the rubber-ducky
that causes this.

The fundemantal problem is that the wavelength at 120Mhz is 2.5 meters.
In order for a radio wave to pass through an opening in a metallic
structure, the dimensions of the opening need to approach a half
wavelength in diameter, and even then the wave is greatly attenuated.
Just to make the point, a half-wave at 120Mhz is 49". How many of the
openings whose edges are defined by the fuselage longerons, the
cross-brace and diagonal brace tubes are 49" across? Answer, none of
them. Even the windscreen opening is usually not that large.
A welded tube fuselage makes a real good "screen room"... Do yourself a
favor, and put the antennas on the outside where they belong...