SUMMARY

In this chapter you learned transmitter and receiver fundamentals. We also discussed modes of operation and special controls circuits. Let's review some of these areas.

A HARMONIC is an exact multiple of the fundamental frequency. Even harmonics are 2, 4, and so on, times the fundamental. Odd are 3, 5, and so on, times the fundamental frequency.

A SUBHARMONIC is an exact submultiple of the fundamental frequency. Even subharmonics are one-half, one-quarter, and so on. Odd subharmonics are one-third, one-fifth, and so on, of the fundamental frequency.

SUPPRESSION is the process of eliminating an undesired portion of a signal.

MULTIPLEXING is a method for simultaneous transmission of two or more signals over a common carrier wave.

An ORDER-WIRE CIRCUIT is a circuit between operators used for operations control and coordination.

RECEPTION is when an electromagnetic wave passes through a receiver antenna and induces a voltage in that antenna.

DETECTION is the separation of low-frequency (audio) intelligence from the high (radio) frequency carrier.

REPRODUCTION is the process of converting electrical signals to sound waves. This sound is speech, music, and so on.

SENSITIVITY of a receiver is the ability to reproduce weak signals. The greater the receiver sensitivity, the weaker the signal that will be reproduced.

Receiver SELECTIVITY is the ability to select the desired signal and reject unwanted signals.

NOISE SILENCER, NOISE SUPPRESSOR, or NOISE LIMITER, are circuits that clip the peaks of the noise spikes in a receiver.

SQUELCH is a circuit that cuts off the output of a receiver when there is no input.

A BALANCED-PHASE DETECTOR or PHASE-DISCRIMINATOR is a circuit that controls the oscillator frequency (afc).

FREQUENCY SYNTHESIS is a signal-producing process through heterodyning and frequency selection.

A PERMANENT MAGNET SPEAKER is one with a permanent magnet mounted on soft iron pole pieces.

The FIDELITY of a receiver is the ability to accurately reproduce at its output the signal at its input.

GANGED TUNING is the process used to tune two or more circuits with a single control.

HETERODYNING is the mixing of the incoming signal with the local oscillator frequency. This produces the two fundamentals and the sum and difference frequencies.

An IMAGE FREQUENCY is an undesired frequency capable of producing the desired frequency through heterodyning.

AUTOMATIC VOLUME/GAIN CONTROL is a circuit used to limit variations in the output signal strength of a receiver.

FADING is the variations in signal strength at the antenna of a receiver.

REVERSE AGC is when an amplifier is driven toward cutoff.

FORWARD AGC is when an amplifier is driven toward saturation.

A BEAT-FREQUENCY OSCILLATOR is an additional oscillator used in a receiver when the receiver is receiving a cw signal and provides an audible tone.