Section 3
Transmitters and Receivers

Transmitter interference

3G1 Recall that excessive amplitude modulation causes distorted output and interference to adjacent channels.

An excessively high level of input audio signal to the modulator results in an excessive amplitude modulated signal, for instance if you shout into the microphone, then instead of a louder sound of your voice in the receiver being heard in fact only a much distorted voice will be heard and depending upon the extent of distortion may nor may not be understood at all. The additional ADVERSE effect of an excessive input, thus overmodulation is that interference to adjacent channels / frequencies may well occur in an Amplitude modulated transmitter.

The problem of excessive input can be prevented by the CORRECT use of the Microphone gain control where fitted to the transmitter.

Recall that excessive frequency deviation will cause interference to adjacent channels.

Also excessive frequency deviation of an FM signal will cause interference to adjacent channels in CB terms "Bleed Over" and thus distort the signal on that channel.

The origin of some of the text on this page is from the RSGB with additions by the web master