FM Operation

Frequency modulation provides many advantages when used for amateur radio communications.

Frequency modulation tends to be used where mobile and portable operation has been more widely used. The reason for this is its greater resilience to noise and signal strength variations when compared to AM.

In view of this, FM has gained very widespread acceptable on the VHF and UHF amateur radio bands, and in addition to this it is also used on the Ten Metre ham radio band as well.

Frequency modulation technology

The technology behind frequency modulation is the same whether it is used for amateur radio or any other application.

Instead of carrying the information, i.e. sound in most cases as changes in amplitude, for frequency modulation, the frequency of the signal is changed in line with the modulating waveform.

frequency modulation signal showing how the modulating signal varies the carrier frequency
Frequency Modulation, FM

Note on Frequency Modulation, FM:

Frequency Modulation, FM is a form of radio signal modulation where the frequency of the carrier signal is varied in line with the modulating information. It is widely used for many applications from small handheld VHF walkie talkies, to high quality VHF FM broadcast transmissions.

As all the modulating information is carried as frequency variations and no amplitude changes are required, the signal can be passed through a limiter stage. This not only removes the major source of noise which is amplitude noise, but it also removes the major changes in signal strength resulting from mobile operation.

In view of these advantages, frequency modulation is an ideal mode of modulation for many amateur radio applications.