On 19-Nov-2006, Mike Spera wrote:

So now what? Some suggested that the Narco nav/coms were not properly
shielded. While others speculated that the interference is coming
straight from the antennas for the nav/com.


There is little chance that interference from a NAV radio would emanate from
the nav antenna -- it's more likely coming from the radio itself. Any
receiver has a lot of internal oscillators that can mix with one another to
create interference in all sorts of frequency bands. If designed well, all
of this RF "crap" should be retained in the receiver through proper
shielding, but not all radios are created equal (que the Narco bashers).

Short of an external GPS antenna, what I would try is to shield the antenna
as much as possible. If you place it on the glare shield, try putting a
shield, in the form of several layers of aluminum foil, between the antenna
and the glare shield. Play around with the shield a bit with the "worst
case" radio nav/com tuning you have found.

-Elliott Drucker