User Manual Part 1

FSG 90F System
2. General Description
November 2000 Page 11
W. Dittel GmbH
Transmit frequency / channel name is tuned simultaneously with Receive frequency /
channel name (Simplex operation).
A keyed transmitter is indicated by a transmit symbol at the LC display.
Two independent microphone inputs (separate pins) allow universal accessory
operation:
• For powered aircraft use Standard Carbon, amplified Dynamic or Electret
microphones,
• For gliders, portable, vehicle mobile, and fixed base operation use non-amplified
Dynamic microphones.
The microphone inputs may also be continuously activated. This allows during Receive
continuous intercommunication (no additional accessories needed) between pilot and
crew (intercom wiring harness), using headsets.
A separate AF input allows interconnection of external audio source(s) especially in
aircraft using other COM, VOR/LOC, DME, MKR and / or electric variometers. This
allows signal monitoring during Receive by speaker and / or headphone.
30 mA current consumption saving can be achieved in standby mode (Squelch ON),
when the FSG 90F(X) is used in installations, where no external audio is required for
speaker output. Listening through headphone remains however possible. This external
AF OFF function may be selected in SET-UP. This reduces the standby current
consumption to only 80 mA and will extend battery supplied operating time significantly.
The transceiver can be supplied either directly from a 12 to 14 Vdc A/C bus, or through
a suitable DC regulator from 28 Vdc-buses.
In aircraft without onboard electric power generation system (UL, Glider etc.), operation
from a rechargeable 12 Vdc battery (min. 6 Ah) is suitable.
The DC supply voltage is monitored continuously while the radio is ON. When supply
drops below 11 Vdc, the Supply Indicator at the LC display starts blinking as a low
supply warning.
Below 8.5 to 9.5 Vdc, the FSG 90F(X) turns OFF itself automatically, and will resume
operation with supply above 9.5 to 10 Vdc. The last used settings remain active.
A voice processor is incorporated to achieve identical acoustic voice quality during
Transmit and Receive, as well as Audio Leveling in Receive, and in addition prevents
overmodulation in both Single and Dual channel spacing Mode. Usual testing employs
sinusoidal tone signals only; this feature especially considers the specific characteristic
of the voice. It ensures also VERY HIGH AVERAGE DEPTH OF MODULATION of
some 80% AM, causing transmission signals sounding normal and very strong.
The radios are equipped with a time out timer. This avoids blocked channel after 2
minutes continuous TX (stuck button does no longer block a channel continuously) and
is indicated by a continuously blinking display. Should the malfunction continue the
FSG 90F(X) is ready for another 2 minutes transmission period when turning OFF and
ON again (e.g. for emergency transmissions).
The transmitter blocking feature avoids transmission on a busy channel. Transmitter
blocking is usually active, but may be disabled permanently in SET-UP or manually by
pushing the SQ button.