Airborne tacan equipment AN/ARN-21

The equipment is designed to receive range and bearing information from a ground-based Tacan beacon. The chief components are the local oscillator, providing a selection of 126 crystal-controlled frequencies at 1 Mc/s intervals from 1025 Mc/s to 1150 Mc/s, the transmitter, which transmits range interrogation pulses of 3.5 musec duration in pairs spaced by 12 musec at a repetition rate of 27 or 130 pairs/sec, and a receiver of 63 Mc/s i.f. which operates the bearing and range display circuits. The local oscillator both controls the transmitter and beats with the incoming signal. A pre-selector is included to protect the receiver mixer crystal from the transmitter and reduce spurious responses. The equipment weighs about 56 lbs. and contains 73 thermionic tubes.