Garmin GNC 420A Installation Manual page 100

5.3.7 VHF COM Check (GNC 420 and GNS 430 Only)
A flight test is recommended after the installation is complete to ensure satisfactory performance. To
check the communications transceiver, maintain an appropriate altitude and contact a ground station
facility at a range of at least 50 nautical miles. Contact a close ground station. Press the squelch disable
button to defeat the automatic squelch feature and listen for any unusual electrical noise which would
increase the squelch threshold. If possible, verify the communications capability on both the high and low
ends of the VHF COM band. It may be required by the governing regulatory agency to verify operation of
the COM transmitter and receiver at the extents of a ground facility's service volume (e.g., FAA AC 23-
8A)
5.3.8 VOR/ILS Check (GNS 430 Only)
Select a VOR channel within a 40 nautical mile range. Listen to the VOR audio and verify that no
electrical interference such as magneto noise is present. Check the tone identifier filter operation. Fly
inbound or outbound on a selected VOR radial and check for proper LEFT/RIGHT, TO/FROM, and FLAG
indications. Check the VOR accuracy. Verify that the flag is hidden with a valid received station, and that
the flag is in view when there is not a received station. It may be required by the governing regulatory
agency to verify operation of the VOR receiver at the extents of a ground facility's service volume (e.g.,
FAA AC 23-8A).
5.3.9 DME Tuning Check (GNS 430 Only)
Select a VOR/ILS channel that corresponds to (1) a DME station within a 40 nautical mile range, or (2) the
frequency of a DME ground tester. Verify that the DME locks on to the signal and a valid distance,
groundspeed and time are displayed.
Page 5-18 400 SERIES INSTALLATION MANUAL
Page Rev L P/N 190-00140-02