Technical data
VHF/AM RADIO FSG 2T
3 Installation
June 2014 FAV_D10048 39
3.5.5 OPTIONAL: AF External Operation
Solder bridge
VOL/SQ Potentiometer
1µF
On the TX/RX module, the optional AF
External Mode is enabled by making a
solder bridge across two small solder
pads, remove one resistor and change
one capacitor. To get access, the radio
FSG 2T must be opened (refer to
Maintenance/ Overhaul Manual FSG 2T)!
Enabling AF EXTERNAL causes
increased current consumption during
Standby, and disables the VOX Intercom
threshold!
IMPORTANT!
The Option AF EXTERNAL can be enabled by an approved Avionics
workshop (see Maintenance/ Overhaul Manual FSG 2T, Circuit Diagram,
Fig. 10-6m and Location of Components, Fig. 10-7) by making a solder
bridge! The Information Label of the radio must then be marked
accordingly.
The AF External Input Pin 4 may be connected to any external (selectable) audio output
of any other audio source. An input of 1 Volt rms (approx. 10 kOhm input impedance) is
required to obtain maximum audio volume. Higher AF input may cause audio distortion.
External AF will be audible only in Receive Mode and in Standby Mode, and may be
heard in the speaker or headphone. During Transmit, the External AF Input is disabled.
Interconnection of external audio source(s) will be suitable especially in aircraft using just
one COM and one NAV. The NAV headphone output may then be connected directly to
the FSG 2T External AF input.
This allows – in addition to the receiving and Intercom function – also simultaneous
listening of COM and NAV audio either by headphones or speaker.
Interconnection of more than one external audio source requires additional external
decoupling / isolation resistors (470 Ohms, refer to Figures 3 - 7 / 3 - 8).
The individual audio volume is set directly at the particular external equipment and may
be reduced by the transceiver's VOL knob.
For audio wiring use only shielded cables to avoid interference from strong electrical
fields. An eventually magnetic interference coupling shall be especially regarded
(distance required from high current carrying wiring).