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March 1946 Radio-Craft
 [Table of Contents]
Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Craft,
published 1929 - 1953. All copyrights are hereby acknowledged.
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The General Electric TDY-2 was
one of the earliest American anti-radar
electronic countermeasures
(ECM) systems. Having been highly secret technology during World War II, its
existence and some details of its operation were revealed in a 1946 issue of
Radio-Craft magazine. Declassification of much advanced technology in the post-war
years fueled the boom in both commercial and consumer markets, including electronics,
communications, automotive, boating, aircraft, appliances, construction, and even
manufacturing and distribution. Interestingly, the time taken to get products into
the marketplace was longer than a lot of people anticipated, and it caused consternation
amongst those hoping to benefit from the promises made by companies toward the end
of the war (see Radio Industry
Unfair?).
Anti Radar Equipment - Cover Feature
Photo A - Ultra-high-frequency anti-radar transmitter partly
open to view. Photo courtesy General Electric Co.
The genius of America's big transmitter manufacturers - now engaged in producing
new high-power, high-frequency equipment for FM, television and communications use
- was devoted up to a few months ago to producing very similar transmitters for
the purposes of electronic war. The radar jamming transmitter shown on our cover
contains many of the features required in peacetime u.h.f. apparatus. A product
of General Electric, it is known as the TDY-2.
Unfortunately, the military use of the apparatus prevents - even at this late
date - publication of facts concerning the exact power or frequency of the transmitter,
though the magnetron tubes used by it give the reader a rather good idea of the
latter. In all the pictures of the apparatus yet released, the top shelf, which
carries the power oscillator and modulator, is modestly closed.
The more prosaic power equipment may be seen in the accompanying Photo A. The
four tubes which are visible on the top shelf of the lower section are high-voltage
rectifiers. Transformers, chokes and other heavy equipment are on the bottom shelf.
The water pump, used for cooling; may be seen behind the engineer's arm.
A special antenna which permitted rotation in any direction, as well as variations
in vertical polarization, was used with this unit. A special "antenna pedestal"
was required, this consisting of a lower stationary part, and the rotating mast
which carried two antennas. The pedestal control-indicator unit both rotates the
antenna mast and indicates the bearing in which jamming signals are transmitted.
Another important part of the anti-radar campaign consisted of detecting and
locating enemy stations, both mobile and fixed (so that jamming signals could be
accurately beamed on them). This device, a great improvement on standard pre-war
direction finders, used a cathode-ray indicator like that in a radar set itself.
Photo B - Direction finder, center, in an array of anti-radar
apparatus.
One of these direction finders, manufactured by the Submarine Signal Co., of
Boston, Mass., is shown in Photo B. It measures the frequency of the signal as well
as the direction from which it came, and could receive successfully even the ultra-high-frequency
signals produced by the very latest radar apparatus. Other apparatus of the radar
counter-measures room, seen around the direction finder, consists largely of receivers
tuned to different portions of the radio spectrum.
Photo C - One signal being received.
Photo D - Pattern for several signals.
Operators handling the new direction finders became so skilled that they could
look at the scope and tell from the image of the intercepted signals what kind of
radar had produced them. It was possible to distinguish between images caused by
anti-aircraft, surface search and gun-control radars. Thus in many cases it was
possible to deduce the size and class of the ship carrying the intercepted radar.
Patterns on the screen when one signal, and when several signals on the same frequency,
are present, appear in Photos C and D.
This capability of occasionally identifying the source of signals was at times
embarrassing to the operators of the radar-finder. In one case during night maneuvers
aboard a destroyer, signals were picked up which could be definitely identified
as coming from a U. S. cruiser. This was accordingly reported to the bridge. When,
some days later, U. S. cruisers were sighted, the captain felt that his direction-finder
men had not been "on the job" because the cruisers' presence had not been detected!
Other apparatus which was developed during the war but which is likely to have
important applications in peace is the Loran system of locating a ship. This is
superior to straight direction finding, as the ship operator can get his position
exactly without having to communicate with the shore stations. Radar may be the
most important peace-time aid to navigation, as it permits entry into crowded harbors
at night or in dense fog with little more danger than in bright daylight. Even railroads
are seriously considering the use of radar as a means of preventing rear-end collisions.
The greatest problem, however, has been development of transmitters capable of
putting out considerable power at microwave frequencies. It will be remembered that
during the discussions on high-definition television which took place last year
one of the chief objections was that it might take years to develop the transmitters
required for the high frequencies involved. The equipment described here and pictured
on the cover should be the answer to that problem. Not alone in television will
such apparatus be useful - there are many applications in sound broadcasting and
continuous wave or pulse telegraphy to which it is particularly adapted.
Posted May 14, 2021
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