2. Superheterodyne scanning interceptor

2.1 Superheterodyne receptor

In radiomonitoring, the reception structure mainly used is superheterodyne reception. As well as allowing the received signal to be translated onto a fixed intermediate frequency for sampling and analysis purposes, this structure is in fact practically the only one capable of providing the high sensitivity and frequency selectivity required. The block diagram of a superheterodyne receiver is shown in figure 1 .

The input stage includes filtering and amplification. Filtering is designed, among other things, to protect reception from interference by harmonic frequencies and to reduce reception noise. It is performed either by a...