Garmin GDL 90 UAT Upgrade Instructions page 14

Installation
comm antennas, or a 1575.42 MHz notch filter may be installed in series with the antenna coax of the
VHF comm transceiver to reduce or eliminate the harmonic interference. A notch filter (part #162-1059)
is available from Garmin AT.
If a VHF comm transmitter causes problems with the GPS on the selected frequencies as listed in the
post-installation checkout, the problem may be due to the ELT. This can be verified by disconnecting the
ELT antenna coax at the ELT unit. If the ELT is found to cause the problem, then contact the ELT
manufacturer or replace the ELT.
To preserve certification integrity, it is important that the GX60 continues providing
power to the GPS antenna splitter, if one is used.
2-6
NOTE
560-1057-00 Rev A GDL 90 Capstone Upgrade Instructions