k. Press the SET key. Verify that a Set-up Page (Satellite Status Page) is displayed
and the annunciator next to the SET key is on.
l.
Press the RTE key. Verify that a Route Page is displayed and the annunciator
next to the RTE key is on.
m. Press the WPT key. Verify that the Select Waypoint Type Page is displayed
and the annunciator next to the WPT key is on.
n. Press the CRSR key and verify that APT? flashes.
o. Rotate the outer function knob clockwise and verify that VOR? flashes.
p. Press the NAV key. Verify that a Navigation Page is displayed.
q. Turn the GPS 155 OFF.
15. Satellite Tracking Test:
The Satellite Tracking Test ensures that the GPS 155 has current almanac information
and is able to lock onto a sufficient number of satellites to provide a position. This test
also verifies that the signal strength of the satellites received is at an acceptable level.
a. Turn the GPS 155 off.
b. Connect the unit to a GA 56 antenna mounted outside with a clear view of the sky, through a coax
with a 10 dB ± 1 dB cable loss @ 1.5 GHz. NOTE: Attenuation pads must not be used since the unit
supplies the GA 56 with DC power. A 10 dB cable is available through GARMIN (P/N 320-00088-00).
c. Turn on the GPS 155. Go to the Satellite Status Page (see Pilot’s Guide for instructions).
d. Allow the unit to lock onto the satellites. If the unit has current almanac data, it will list the visible
satellites on the row labeled ‘SAT’ and will begin acquiring satellites in a period of a few minutes. If the
unit indicates ‘SEARCH SKY’, instead of ‘ACQUIRING’, it must search the sky for available satellites and
collect almanac data. A “search the sky” operation may take 20-30 minutes to complete.
e. The unit must enter 3D navigation mode, upon completion of “acquiring” or “search the sky”
operations.
f.
The unit must display the following:
1) 4 satellites with signal strength of ‘3’ or greater.
2) The average signal strength on satellites above 20° elevation shall be greater than or equal to
3.5 (see Pilot’s Guide for instructions). Satellites that are acquiring should not be included in
the average signal strength calculation.
26
