What could be happening if another operator reports a variable high-pitched whine on the audio from your mobile transmitter?

When another operator reports a variable high-pitched whine on the audio from your mobile transmitter, it is likely caused by noise from the vehicle's electrical system. This type of interference can occur due to various electrical components in the vehicle such as the alternator, ignition system, or other electronic devices that generate electrical interference.

As your voice is transmitted, this noise can also be picked up by the microphone and mixed with your audio, creating an undesirable whine that varies with engine speed or electrical load. This scenario is common in mobile setups where the radio is powered by the vehicle's electrical system.

Adjustments like squelch control or receiver volume can help manage unwanted noise but won't eliminate the interference originating from the vehicle's electrical system itself. Understanding this interference helps operators troubleshoot audio quality issues effectively while using mobile equipment.