The Murphy Builders Site

Hello! I've got a simple question about the placement of the vhf comm
antenna. I notice from the Murphy literature that they placed the antenna
behind Bulkhead B. For reasons of convenience I'd like to install it just
behind Bulkhead A. With the two skylights between Bulkheads 9 and A, would
this leave a sufficient ground plane so as not to lose good rf energy into
the cockpit? The only rule I could find suggests a 24-inch diameter ground
plane but also says this could be accomplished with four foot-long strips of
copper foil in a composite a/c.

Many thanks!
Jeffrey Steenson (E714)




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Hi Jeffrey !

For what it's worth, I've found it convenient to mount the
comm antenna on the metal strip that fills the gap between the
wing & fuselage. This makes it easy to get at for service, and
easy to run a shorter lead to the radio. This position also
gives a terrific ground plane along the wings. It's also a good
spot to mount the GPS antenna (on the opposite wing root).

I have also tried mounting them on the top of the fuselage,
behind the skylights, but this area needs a lot of extra supporting
doublers to quiet the vibration, and distribute the load from the
antenna, and doesn't work quite as well as the wing root.

Did mount a nav antenna between the skylights on one
Rebel - it worked ok, but again, needed extra bracing.

......bobp

---------------------------------orig.-------------------------------
At 08:40 AM 11/3/02 -0700, you wrote:

Hello! I've got a simple question about the placement of the vhf comm
antenna. I notice from the Murphy literature that they placed the antenna
behind Bulkhead B. For reasons of convenience I'd like to install it just
behind Bulkhead A. With the two skylights between Bulkheads 9 and A, would
this leave a sufficient ground plane so as not to lose good rf energy into
the cockpit? The only rule I could find suggests a 24-inch diameter ground
plane but also says this could be accomplished with four foot-long strips of
copper foil in a composite a/c.

Many thanks!
Jeffrey Steenson (E714)


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