Garmin SL40 won't Transmit

[Design4p]

My Radio is a Garmin SL40.

I Flew recently and with airfield information and a radio strength 5 took off.

Changed frequency to Shawbury Zone and requested basic service. Later I wanted to change frequency to London Information. Made my request to Shawbury but only manage a dull silence in my headset, although I could hear all incoming communications. The controller asked if it was my call sign trying to transmit, and if so, ask me to press the IDENT button on my transponder.

My radio will receive at radio strength 5 but transmitting is zero.

Regarding sidetone - When I press to talk there is a split second where everything is normal then the sidetone disappears and all is quiet and dull in the headset.

On the ground I tested the two way communications with a handset transceiver and the aircraft radio. When I try to transmit from the aircraft radio the handset gives out a loud buzz.

I would be most pleased if a solution can be found.

Regards John

[Uplinker]

First thing to check is the power supply to the radio.

A transceiver uses much more power to transmit than to receive. If the source of power is (current) limited, then the set may well receive perfectly but "fall over" when trying to transmit.

I don't know the Garmin. Does it use its own on board batteries, or external power? If it uses its own batteries, are they a make with decent performance e.g. Duracell professional.

If it uses external power, get a multimeter and check the voltage feeding the set. If that is healthy, then if you can, check the voltage when the set is transmitting and see if the voltage drops significantly.

The loud buzz: was that with the aircraft engine running? A buzz suggests power supply faults, alternator problems, or possibly earthing faults/ miswiring.

If the power supply is good, then the set transmit might be faulty. The transmitter could have failed and only working at very low power - giving a very short range. When you said you had strength 5; was that reported by the tower? Is it a new set or one you have used successfully before?

[i am a bee too]

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