This does not pertain to the comm selector channel spacing.

With the evolution and growth of airborne travel and the necessity for more usable frequencies in the VHF communications spectrum, the "channel" spacing became smaller. To avoid interference between channels the bandwidth of the RF stages was decreased from 50khz to 25khz. In doing so, another problem was introduced. If the ground transmitter or the air to air transmitter was not capable of tighter frequency tolerances, it was possible the 25khz RF selectivity would not allow the receive signal to pass and the aircraft crew could miss critical voice communications.

Due to the presence of older, outdated equipment in some countries, some manufacturers (namely Bendix/King and Collins) produced VHF comm radios with the 50khz receiver selectivity. With the recent mandates and technological advancements in Europe and South America, the requirements for the 50khz versions has diminished. If an operator were to use a 50khz version radio in the position of a 25khz, they would potentially have channel crossover and or an increase in background noise.

The VHF-22C is only a direct replacement for the VHF-22A 25 kHz comm. The VHF-22C is not a direct replacement for the VHF-20A or VHF-21A radios as they have different mating connector styles. The VHF-22D is a direct replacement for the VHF-22B.

Negotiating the exchange price of a unit only limits the allowable repair cap for the core unit. Southeast Aerospace's exchange transactions are based on the return of economically repairable core unit. Once the core is received and evaluated, the core repair cost incurred by SEA cannot exceed 80% of the original exchange price. That is, it cannot cost SEA more than 80% of the original OH/SV exchange price collected from the customer. Therefore, when and if an SEA exchange price is discounted, there is a risk that additional charges may be assessed once the core is returned and evaluated.

For more information, please refer to these other Exchange FAQs