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Communication

4.13.4 SQUELCH

Squelch (SQ) is a device for suppressing hiss and noise when there is no speech

on the frequency. It is set either manually or automatically and so that the noise

is just gone when the receiver is at rest.

It affects the receiver's sensitivity. It must be set carefully.

This function is not available on regular aircraft radios, but on most handhelds,

so be aware of it if you have a handheld on the plane.

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4.14 Emergency radio equipment

As a rule, emergency radio equipment in an aircraft consists only of a battery-

powered transmitter.

The transmitter is activated either manually or automatically if it is subjected

to strong shocks such as from a crash or a hard landing.

If it is exposed to moisture or water, it will also starts working.

Emergency transmitters send a signal that can be detected by rescue personnel

and can be heard if we tune to the emergency frequency 121.5 MHz.

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© marts 2026 436