In 1944, ARC produced a small number of tunable VHF sets for Navy evaluation. There was never a follow-on contract, though as noted below the receivers became the foundation for postwar ARC commercial VHF sets produced in the thousands. Shown here is almost the entire installation diagramed in the brief supplement to the ARC-5 manual (missing only the T-89 100-125MHz transmitter). From left to right, MD-7 modulator, R-113 and R-112 receivers (C-29 transmitter control and RE-16 antenna relay suspended above), and T-90 transmitter (125-156MHz.) Following ARC's penchant for reusing components that met their stringent requirements from other sets, both the RE-16, T-89, and T-90 used the same antenna relay contained in the more common AN/ARC-3 VHF transmitter. The RE-16 also contained a 12H6 rectifier used to rectify the carrier for an antenna voltage indication (as opposed to the the usual antenna current meter), and two control connectors so that a normal HF set antenna relay could be daisy-chained through it. That allowed a single C-29 control box to control both HF and VHF sets.

The receivers eventually morphed into the postwar ARC Type 12 and later VHF sets with very little change other than paint color, loctal tubes, and elimination of the brass wired IF transformers designed to broaden the response curve for aircraft comms at the time. The front end preselector, using four miniature vacuum tubes, is a marvel of careful parts placement and design. The local controls, unique to these two receivers, had black lacquered sheet metal blocks placed on the mode switch to prevent selection of CW, which of course didn't exist in this set.

Production figures are said to be in the region of 100 or so. Some of these sets received official Navy nomenclature tags and were actually tried out in the Fleet. The 125-156MHz receiver on the left in the photo above is serial number 3! Others, like this T-90 from the ARC Morgue, had only the model number stamped on the outside.

This equipment used a coax link between sets in each rack that was unique to them. It was a sort of home-brew hardline to minimize losses. A photo of these hardlines is below, with some new ones below the originals before silver plating is applied. You can see some of the reproduction efforts for these hardlines over on the Garaj Mahal web page (under "Coax connectors").



The transmitters were of fairly conventional design, using a MOPA approach with an intermediate 832 frequency multiplier. for the design. As with all the ARC low volume equipment, these are finished like Swiss lathes and great care was taken to ensure mechanical rigidity. This was especially important since there is no crystal to establish initial stability - the crystal in the enclosure is for calibration only, identical to the lower frequency units. A Sylvania SD-838 prototype tube was used as the Master Oscillator - a 28v filament triode that was necessitated by the lack of complimentary tubes to use within the transmitter for a series filament string. Data on the tube is recorded on a piece of paper pasted onto the glass envelope! More photos of this transmitter are below.

Front view

Top view



Rear top tag



Right side view of interior

Rear view of interior. Serial # is B2, not 82, signifying a set that wasn't released to the Navy for evaluation.

Detail of antenna relay. This was "borrowed" from the AN/ARC-3 VHF transmitter
that was essentially a competitor for this set.
ARC was not above using a good component from somewhere else when it filled the bill.


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