FSG 70/FSG 71M
O
PERATION
M
ANUAL
Page
2 - 2
Reprint July 1998
W. Dittel GmbH
2.3
Brief Description
The
FSG 70
and
FSG 71M
are miniaturized lightweight panel mounted transceivers
designed to operate in the VHF-COM frequency range from 118.000 to 136.975 MHz
in 25 kHz increments, thus providing 760 channels over a standard communication
distance of 100 nautical miles at FL 70.
The case dimensions fit into a standard 2¼" cut-out of the instrument panel. Only four
screws (M 4 x 16) are used to install the transceiver units. Electrical connections to the
environment are made through a 15-pole SUB-D connector and a BNC female
connector at the rear panel of the units.
The operational frequency is displayed by means of a Liquid Crystal Display with five
digits following the ICAO-scheme:
The least significant digit is omitted (e.g. 127.875 is displayed as 127.87 MHz).
The transceivers consist of five main sections: Digital frequency synthesizer, receiver,
transmitter (6 watts carrier, 24 watts PEP), audio circuits, and LCD frequency display
circuitry.
Model
FSG 71M
includes an additional section:
A non volatile electronic ten channel memory. This memory and its command controls
make the only difference between
FSG 70
and
FSG 71M
. The operational frequency of
the
FSG 71M
unit is indicated by the LCD and may be selected in two modes on the
front panel:
a)
Direct mode:
The channel control knob on the right front side must be set to full
ccw position. By using the MHz/kHz coaxial double knob on the front panel all 760
channels may be selected as usual.
b)
Storage mode:
The channel control knob is set to select the desired channel for
any "Read" or "Store" action. Up to 10 out of 760 channels may be programmed
and permanently stored for up to five to six years in the electronic memory. Storage
channels may also be reprogrammed if necessary, even in flight.
The
FSG 70
has no channel control. Frequency selection can be performed only in
direct mode using the coaxial double knob.
Further features incorporate an automatic squelch circuit with manual override and
automatic adaptation to pulsed noise, separate microphone inputs for low level
dynamic and standard carbon mikes, compressor for modulation level control, a
"transmitter ON" annunciator LED, an intercom mode ,a wide supply voltage range of
9.7 to 15.2Vdc, audio lowpass filter for CLIMAX environment, additional AF input for
application of external (e.g. NAV-) audio, internal lighting of the frequency display and
a very comprehensive indication of "Low Supply" by flashing of the frequency display.
Audio output is delivered separately for speakers (receive only) and for headphones
(receive and transmit sidetone).
The transceivers can be supplied either direct from 12/14Vdc-buses or via a voltage
converter (Type S20000) from 28Vdc-buses.
An automatic power-saving circuit prevents unnecessary power consumption in some
operating modes, thereby extending the operating time available from one battery
charge. Particularly the no-signal current drain in the squelch (SQ) mode is reduced to
the very low level of approx. 25 mA.
