FSG 70/FSG 71M
O
PERATION
M
ANUAL
Reprint July 1998
Page
3 - 1
W. Dittel GmbH
Section III
Installation
IMPORTANT!
•
Switch always OFF the radio before connecting or disconnecting
the receptacle plug! This is a simple precaution which helps to
protect the solid state circuitry and extends the operating life of
your avionics equipment.
3.1
General
This section contains instructions and suggestions for installing the
FSG 70/ FSG 71M
in an aircraft.
3.2
Pre-installation Check
Carefully remove the transceiver packing and save in case a claim has to be placed
with the shipper.
Check for conformity between delivery note and goods delivered. Check the unit
carefully for external damage. Before installing, a check of the main functions is
recommended:
1. Connect the unit to a test bench, using the test cable set (shown in Fig. 3-2).
Ensure 13.8Vdc operating voltage, and switch on the unit (right toggle switch "ON").
SQ-switch "OFF" (left toggle switch down).
2. Turn volume control about half-way open (clockwise). Slight receiver noise should
be audible on all channels in the range from 118 to 136.975 MHz. Receiver
sensitivity should be equal the technical data on all channels (check by sample
test).
3. Push left toggle switch upward (SQ), vary VHF generator output voltage and
observe the squelch threshold; it must be between 0.5 µV and 3 µV (depending on
setting).
4. Connect RF test set-up with RF load resistor (50 Ohms) at the antenna output.
Transmit and measure the output power (
≥
6 W).
5. Connect 1.000-Hz audio generator through a voltage divider or directly (low
level/high level microphone) to the microphone input.
a) High level input (Standard Carbon mike)
With an AF input voltage of approx. 100 mV
eff
the transmitter should be > 40%
modulated. Raise the AF input voltage to 1.0V. Observe the envelope; a
continuous over-modulation must not occur. The depth of modulation must not
exceed 95%.
b) Low level input (Dynamic microphone)
With an AF input voltage of approx. 1mV
eff
the transmitter should be > 40%
modulated. Raise the AF input voltage to 10mV. Observe the envelope; the
depth of modulation must not exceed 95%.
IMPORTANT!
•
With voice modulation, greater depths of modulation occur because of
the dynamics typical of speech (quick level changes). Setting the
modulation control to approx. 85% (for sine modulation) results in a
favorable compromise between carrier utilization and over-modulation.
