Direct Gain Receivers

Figure 2.5.

This type of receiver differs from a detector receiver with an AFF amplifier having an amplifier at the signal frequency.

To obtain high sensitivity and selectivity in such receivers you need to use a large number of resonant amplifiers tuned to the frequency of the signal (4-5 and more). Since the receiver is usually intended to receive not one carrier frequency, but several fixed frequencies or, more often, a smooth frequency range, all circuits should have tuning organs, i.e. variable capacitance or inductance. This circumstance would significantly complicate the design of the receiver and would make it difficult to maintain the constancy of the electrical parameters of the MSS within the entire range (constant gain, bandwidth, selectivity).

Therefore, it turned out to be a natural transition from direct amplification receivers to frequency conversion receivers - superheterodyne receivers.