Transceivers

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

A radio that combines both a transmitter and receiver is called a transceiver.

The main items associated with the transceiver are:

• Microphone — used to transmit messages.
• Speaker or headset — used to listen to received messages.
• Electrical or avionics master switch — provides electrical power to the radio equipment.

Adjustment of the controls of commonly used aeronautical transceivers.

Squelch Control

The squelch control suppresses unwanted background noise from the receiver when no useful radio signal is being received.

It may be:

• fixed automatically by the radio; or
• adjustable by a knob or sequence of button presses.

Adjustment

When manually adjusting the squelch:

• adjust the control until background noise can be heard;
• then adjust it in the opposite direction until the noise just stops.

At this point the unwanted background noise is squelched, while a sufficiently strong radio transmission will still be heard.

Caution: If the squelch is set too high, a weak but wanted transmission may also be suppressed.

Microphone Techniques (PTT - Push To Talk)

Good microphone technique is important for clear radio transmissions.