What must be set between TACAN sets in air-to-air mode to simulate the transmit and receive frequency spacing?

In air-to-air mode, TACAN (Tactical Air Navigation) systems must be set to a specific frequency spacing to ensure proper operation and accurate navigation. Selecting frequencies 63 channels apart creates the necessary spacing to effectively simulate the transmit and receive frequency separation. This configuration enables the TACAN system to function optimally by minimizing interference and allowing for clear signal reception between aircraft, facilitating accurate distance measuring.

The reason why 63 channels is the established requirement is due to the design of the TACAN system, which utilizes a specific frequency band structure where each channel corresponds to a particular frequency. The setup ensures that each aircraft can communicate and navigate effectively without cross-talk or confusion in the signals being transmitted and received. Such precise channel spacing is crucial for tactical operations, where accurate positioning and navigation are paramount for mission success.