Transceivers

Aircraft are generally equipped with at least one communications radio set operating in the Very High Frequency (VHF) range.

These radio sets are both a transmitter and a receiver and are called Transceivers.

The items associated with the main transceiver in the cockpit are:

• Microphone used to transmit messages;
• Speaker/headset for listening to received messages;
• Master switch(electrical) to give power supply to the radio;        

Adjustment of the controls of commonly used aeronautical transceivers.

Squelch Control

May be fixed or adjustable with a knob or a sequence of button presses.

The Squelch is a circuit function that acts to suppress the audio output of the radio receiver from weak signals, such as atmospheric noise, in the absence of a strong input signal, such as a signal from a control tower or another aircraft.

Typically the operator will adjust the control until the unwanted noise is heard, and then adjusts in the opposite direction until the noise just stops.

ie: the noise is squelched.

At this point the weaker noise signal is suppressed and when a weak or stronger radio transmission signal arrives that signal will be heard.