In article ,
Ross Richardson wrote:

This is a known problem with Com transmitters and GPS receivers,
especially with the older units. If I remember it is something like the
10th or 11th harmonic of the COM that can interfer with the GPS. I first
noticed it with my old Appolo 2001 that on certain transmit frequencies
the GPS would blank out. I contacted the manufacturer and they provided
me a paper which included something like 20 frequencies in the aircraft
band that could cause this. I check them and sure enough some did and
others did not. Also it is/was how close the two antennas are.


I really meant to say "RFI." You are correct. I seem to remember
reading a warning in the Garmin 430 installation manual that mentioned
routing the antenna cable as far away from the com installation as
possible.



JKG