Page 434 - PPL BEG-engelsk

Communication

This is called amplitude modulation (AM).

The audible tones have a lower frequency than the carrier wave.

4.13.2.4 A3E

A3E is the name of the waves we transmit when

we talk on the radio from an airplane.

It is not far from modulating the amplitude with

an audible tone to modulating it with speech. All

that is required is a microphone.

4.13.2.5 F3E / FM

This way of modulating is called frequency modulation (FM).

Here the amplitude is

constant, but the frequency
changes.

These waves are called F3E and are used for vehicle communication.

4.13.2.6 VHF and UHF

VHF and UHF radio waves propagate in straight lines from the transmitter.

There must be a “line of sight” (you must be able to see each other) between

the stations. The maximum range depends on the transmitter output power

and is usually up to about 200 NM.

To be able to reach this far, the aircraft must be at a certain height above the

surface.

We have a formula for range that says:

Range in NM = √ x 1.23

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© marts 2026 434