ATR833 / P/N 833-(1xx)-(1xx)
Operation and Installation
3.9 Microphone Settings
The settings of MIC and VOX values are essential for Intercom.
(MIC=Microphone level see 2.8.4, VOX=threshold level see 2.4.3).
Using VOX the threshold level is adjusted so that usual flight noise is not
transmitted to the headphones, but only an additional signal caused by
speaking will start intercom operation. With very strong background
noise or uncompensated microphones VOX can be deactivated by
setting VOX=01 (see 2.4.3). In this case intercom is activated using the
intercom switch (not PTT), which connects pin 7 (intercom) of the
equipment connector to GND.
If necessary, e. g. in a tandem cockpit, use two parallel connected PTT
buttons.
For operation in VOX mode pin 7 has to be connected to GND
permanently.
Transmission merely operates when PTT is pressed.
The suppression of background noise is only possible using differential
microphones, as they are usual with modern headsets. Normal electret
microphones are not suitable.
3.10 Post-Installation
Check
A certified maintenance shop must verify proper operation of
the VHF Transceiver System.
When installation is completed all steering and control functions of the
aircraft are to be examined, in order to exclude disturbances by the
wiring.
The SWR shall not exceed 3:1.
Furthermore a test flight is recommended, in order to guarantee the
proper in-flight operation of the radio:
•
In a flight altitude of at least 2000 ft contact a ground station in a
distance of at least 50 km (30 nautical miles).
•
Pay attention to unusual electrical interference.
•
If possible, perform the radio test on frequencies within the upper
and lower VHF communication frequency range
34
Dokument-Nr.: 01.1402.010.71e / Revision: 1.01
