2-15
Figure 2-11.—Comparison of AM and ssb transmitted signals.
Ssb communications systems have some drawbacks. The process of producing an ssb signal is
somewhat more complicated than simple amplitude modulation, and frequency stability is much more
critical in ssb communication. While we don’t have the annoyance of heterodyning from adjacent signals,
a weak ssb signal is sometimes completely masked or hidden from the receiving station by a stronger
signal. Also, a carrier of proper frequency and amplitude must be reinserted at the receiver because of the
direct relationship between the carrier and sidebands.
Figure 2-12 is a block diagram of a basic ssb receiver. It is not significantly different from a
conventional superheterodyne AM receiver. However, a special type of detector and a carrier reinsertion
oscillator must be used. The carrier reinsertion oscillator must furnish a carrier to the detector circuit. The
carrier must be at a frequency which corresponds almost exactly to the position of the carrier used in
producing the original signal.
Figure 2-12.—Basic ssb receiver.
