Safety-Conscious Utilization
14 VHF Transceiver 0638.420-071 Issue 06 02/2021
• Excessive pulses on the DC bus of the aircraft can cause
damage on electrical circuits of any installed instrument.
• Do not turn on the device during engine start or shutdown.
First make a voice communication test before starting any
operation.
• Please notice that, if the communication test is done close to a
ground station, the results may be positive even if the antenna
cable is broken or short-circuited.
Caution! Then a communication could be not possible at a
distance of 5...10 km and above.
• Speak always loud, clear and not too fast for optimal voice
communication.
• Keep the microphone always close to the lips otherwise a
special suppressing circuit
in the VHF COM will not be capable
to suppress normal noise.
• Use only microphones or headsets which are suitable for
specific installations.
o In aircraft made of wood, synthetic materials or in gliders
or helicopters, incoming radiation can affect the
integrated amplifier of the microphone (feedback), then
the ground station receives a whistling and/or heavy
distortion.
• If the power supply voltage is less than the adjusted threshold,
the display shows the message "LOW BATT".
• If the power supply voltage is < 10.25 V, the device continues
operation with decreased performance.
o The speaker output of the transceiver is automatically
turned "OFF"
o The speaker symbol is no longer shown.
o The user must use headphones to continue listening.
• If power supply voltage is < 9.0 Volt, the device turns off
automatically.
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