TACAN beacon simulator.



This early  stand-alone TACAN tester was placed on the platform, a few meters from the aircraft. Bearing and range were set on the tester, and will be received by the on-board TACAN set ARN21B when channel 3 (964 MHz) or channel 118 (1205 MHz) is selected.  Bearing and Range should become visible on the cockpit instruments.

This tester emits no squitter pulses, but a continuous ID tone with equalize pulses.  The tester is powered by 115 or  230Vac  via a long cable.


This all-tube tester was built by LMT in France to test the ARN21.


The tester is also used in the workshop.  For this purpose, a cable with N-connector and HN connector, a 40dB attenuator and a handbook are supplied as part of the system.

To test an ARN21 tacan on the platform



The tester contains 20 tubes, a few diodes, and 3 transistors in the power supply. The complete pulse pattern is generated by free-running oscillators and monostable multivibrators. This required a lot of adjustments inside.


 The transmit frequency is crystal controlled, with a frequency multiplier module that is nearly identical to the one in the ARN21B set.  The crystal oscillates at 26.777 MHz, giving 241 MHz after two triplers. Finally, there is a diode multiplier, the fourth or fifth harmonic should be received by the TACAN set on CH3 resp. CH 118. The receiver in the tester is just another diode, sufficient to receive aircraft pulses of 500W or more over the whole band.


The circuit diagram and some additional data is here.