Cubic Corporation EDM (Electrotape)

Description:

The Electrotape DM-20 is a transistorized microwave EDM. The first commercial

unit, serial number 151, was unveiled in 1961. It yielded centimeter accuracy over

distances from 100 meters to 40 kilometers, and in all weather conditions, day and night.

Each unit cost about $6,000 and weighs about 25 pounds. For use, two units are needed,

one to send the signal and the other to receive it. The DM-20 at the Smithsonian, serial

number 402, was probably made in the early 1960s. The DM-20 remained in production

for about 20 years.

Cubic Corporation, founded in San Diego, California, in 1949 by electronics

engineers from Consolidated Vultee Aircraft (Convair), specialized in microwave

instruments. Their involvement with edms began in June 1958 when the United States

Army Engineer Research and Development Laboratory (ERDL) asked them to develop a

domestic equivalent of the Tellurometer MRA/1. The first Micro-Dist, as the instrument

was then known, was delivered early the next year. Like the Tellurometer, Micro-Dist

used data compression by means of modulation side-band folding. With Micro-Dist,

however, the two units were interchangeable. Other differences pertained to Cubic's

diplexing system, receiver, and manner of digital readout. Micro-Dist operated at 10

Gigahertz. Cubic claimed an accuracy of 1:150,000 ± 2 inches. Micro-Dist was advertised as early as March 1959. In 1960, owing to a conflict with Tellurometer's Micro-Distancer, Micro-Dist was renamed Electrotape.

Ref: Cubic, Instruction Manual for Model DM-20 Electrotape.