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STC, Standard Cables and Telephones, was the British ITT in Southampton that made its own ARN-21 for the RAF (and Dutch Airforce) Pictures of all tubes in the British version are in the Virtual Valve Museum
You can download the circuit diagrams here :
ST ARN21 RF circuit ST ARN21 Video and azimuth circuit ST ARN21 Modulator and Range circuits ST ARN21 Power Supply |
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A tribute to its inventor, Sven H. Dodington. |
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VINTAGE AVIONICS |
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British STARN-21 |
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The British decided to make their own AN/ARN21 with all-British components, compatible with the rack mount and cockpit instruments from the ITT-made ARN-21. The British unit, called the STARN21, is made and advertised by STC. There are many differences, to note some: The STARN21 has 106 tubes because double function tubes ( like double triodes) are not used. The transmitter cavities are gear driven, not by a chain Therefore, the transmitter is directly behind the front panel, and the modulator is near the range electronic cards. The tuning motor is a 400Hz ac motor rather than a dc motor. When the range motor must stop, it is left open in the STARN21, rather than shorted as done in the ARN21.
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