Avionics bending: VHF Comm tuning panel

Three VHF (Very High Frequency) communications systems (referred to as the VHF systems) are installed on the airplane.

The VHF systems supply line-of-sight voice communications with ground stations or other airplanes. The VHF systems operate in either 8.33 kHz or 25 KHz increments from a frequency range of 118.00 MHz to 136.975 MHz.

Each VHF system uses 28-volt dc power. The VHF system circuit breakers are located on the overhead circuit breaker panel, P11.

The left VHF system uses power from the dc standby bus and the right VHF system from the right dc bus.

The center VHF system uses power from the left dc bus.

Each control panel contains two frequency controls and displays, two frequency-in-use lights, and a transfer switch.

Each frequency control has two concentric knobs to change the frequency. The outer knob rotates to change the ones, tens, and hundreds units; the inner knob changes the tenths and hundredths units of frequency.

The transfer (TFR) switch can select either displayed frequency. When set, the selected frequency display shows -ACTIVE-.