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  ARN-21B

  STARN-21

  ARN-52

ARN-52 unit in Starfighter F104 format

A tribute to its inventor, Sven H. Dodington.

VINTAGE AVIONICS

AN/ARN-52  TACAN

The two black modules contain the mechanical servo/synchro systems for range and azimuth. The bearing module has a synchro output to drive the CDI and  RMI instruments, while the Range module only has two potmeters  for the autopilot and a PHI-4 indicator.

 

The other modules are the Bearing :  decoder , “A” and “B” modules, Range : decoder, “A” and “B” modules, and on the lower row the power supply and  magnetic amplifier.

The large module (lower left)  contains all the RF parts. The backbone of this module is the gold-plated cavities block with  four 2C39A type disc triodes as drivers and final amplifier . ( Shown below in upside-down position)  The cavities are tuned with a long shaft, which also rotates the turret with 126 crystals, one for each Tacan channel and some multiplier tuned circuits.  Also attached to this backbone are on the frontside  the oscillator / multiplier, and the IF amplifier, and on the rear side  the (solid state) modulator and the channel motor controller.

Only the modulator and power supply are solid state, all other units have tubes.

The  regular  ARN-52 is built in a square box with a standard 45-pin connector like the ARN21.

The Starfighter version shown here  has a slightly different shape to fit in the F104G Starfighter avionics bay and has two 34-pin M-series connectors. The unit was made by Standard Electric Lorenz (SEL)

 

Circuit diagrams are here:

 - RF  module ( PA,  oscillator/multiplier, IF amplifier and modulator)

 - Range circuits   (Decoder, A , B and mech. module, SelfTest and Limited Search option)

-  Azimuth circuits ( Decoder, A, B and mech. module, magnetic amplifier)

-  Power supply , backplane relays, main connectors.

In 1963, the ARN-21 was followed up by the ARN-52, supporting the A-A mode, had  built-in indicator couplers,  a bidirectional azimuth search, and fast short-range search. Except for the modulator and power supply, the unit  still has only tubes.

The external coupler CU-395 /ARN  as used with the ARN21 to drive the  Course Deviation Indicator (ID-249 ) and Radio Magnetic Indicator ( ID-250) is no longer needed..