Becker AR 4201 - Testing after Installation; Ground Test with Engine Shut down; Ground Test with Engine Running

5. Testing after installation
A. Ground test with engine shut down.
(1) After installation of the unit, measure the antenna tuning between the
base of the antenna and the antenna connecting cable using a VHF
reflection-coefficient meter (voltage standing wave meter).
(2) The VSWR (voltage standing wave ratio) over the complete frequency
range of the unit shall be within 3:1. If this matching value is incorrect,
this indicates a mismatch, caused for example by an incorrect or unsatis-
factory counterpoise, a cable with an impedance which deviates signifi-
cantly from 50 Ohm or an incorrectly tuned antenna.
(3) After the antenna measurement, check the readability by carrying out a
speech test with a ground station.
B. Ground test with engine running.
(1) With the engine running at cruising speed check that the aircraft power
supply is within the permissible tolerances at approximately 14 V.
(2) When performing the succeeding speech test, ensure that the distance
from the ground station is as great as possible, at least 100 m. With the engi-
ne at cruising speed, the cabin noise of the aircraft should be only slightly
transmitted and communication should be clear and distinct. Hold the micro-
phone close to the lips when speaking.
(3) Switch on the aircraft intercom using the IC switch (if fitted) and carry out
a speech test with the engine running at cruising speed. If necessary, adjust
the IC volume (refer to the service mode in the operating instructions (secti-
on 3)).
(4) Switch on the squelch switch and check the squelch function. The point at
which the squelch operates is set in the service mode (refer to operating in-
structions, section 3).
(5) The sidetone volume can be adapted to the cabine noise in the aircraft. If
necessary, adjust the sidetone volume (refer to the service mode in the ope-
rating instructions (section 3)). When using the loudspeaker, the sidetone
should be adjust so that no acoustic feedback occurs.
INSTALLATION AND OPERATION
AR 4201 - ( )
Page 2-9
23-10-01 December 15/95