Transmitters and Receivers

Revision part 1

Learning outcomes of this part

• Know the block diagrams of CW, AM, SSB and FM transmitters.

• the functions of the microphone amplifier, AM/FM modulators, SSB balanced modulator, side band filter, oscillator, power amplifier and low pass filter.

• the relative advantages and disadvantages of a crystal oscillator and a VFO.

• the resonant frequency of the tuned circuit in a VFO determines the frequency of oscillation.

• the stability of an oscillator can be improved by rigid mechanical construction, screening the oscillator enclosure, and using a regulated DC supply.

• a lack of stability (drift) may result in operation outside the amateur bands.

• most modern oscillators are digital synthesizers, which are very stable.