AN/TRC-97A Radio
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The AN/TRC-97A Radio Set, or TRC-97, is a radio set that has 24 multiplex channels and 16 telegraph channels connected to an analog radio. The radio set is a fixed terminal that can transmit up to 40 miles straight line of sight at up to 1 watt, using a traveling wave tube amplifier, or 96 miles in tropospheric scatter at up to 1 kilowatt, using a tunable klystron amplifier, at a frequency range of 4.4 to 5 gigahertz.
The TRC-97 can be connected to one of three mobile antennas, depending on the distance and signal strength needed. One such antenna that can be used with the TRC-97 is the MRT-2 parabolic tropospheric antenna, which is designed to cover distances of up to 160 km, or 96 miles. Another antenna was a simple feed-horn type mounted on a 30 ft pole. These antennas are transported on trailers and have to be manually erected every time they are used, so knowledge of mechanics as well as electronics was needed to erect and maintain that equipment.
Three modes of propagation could be used; Tropospheric scatter, Obstacle Gain Diffraction, and Line of Sight. Tropospheric Scatter and Obstacle Gain Diffraction typically used the 1 kW Klystron while the Line of Sight mode used the 1W Travelling Wave tube.
The receiver of the TRC-97 can pick up very faint radio signals as low as -100 dBm. It uses tunnel diodes, which utilise quantum mechanics theory, to amplify those very low signals. The signals from the two receivers are then sent to a comparator, where they are compared, combined, or used separately, if necessary.
The TRC-97 was initially made for the Marine Corps to help them with their military operations, such as the Vietnam War. It originally only had only 12 multiplex channels, but when the Air Force decided to use the fine piece of equipment, they added an additional 12 channels in another module called the baby mux, next to the cabinet that houses the klystron. Under the care of the Marines, the radio set was expected to live only three months, but when the Air Force took over that versatile radio set, they had been using it for more than 20 years in the 1980's.
The TRC-97 Radio Set is quite small, as radio sets go. It is housed in a van that is little more than 5'6", and is delicately loaded onto a M1028 pickup truck. A trailer hauling a twin set of parabolic antennas is usually pulled by the truck when it goes on its many maneuvers and deployments in support or the American defence system.
The TRC-97 was superseded by a more modern, less maintenance intensive, digital radio set called the AN/TRC-170.
There are several military organisations that have used the TRC-97. One such organisation was the 601st Tactical Control Wing, headquartered in Sembach Air Base, near Kaiserslatern, Germany, which has one of the largest concentrations of Americans outside of the United States. The 601st and 602nd Tactical Control Squardons fell under the 601st Tactical Control Wing, and military personnel assigned to those squadrons often went on deployment to various sites in Germany, thereby providing a show of force during the cold war.
The 602nd Tactical Control Squadron was located in Turkheim, Germany, which was a remote village in Bavaria. The nearest military intstallation was an Army installation in Nue Ulm, Germany. The 602nd Tactical Control Squadron closed in 1985, when the United States agreed to minimise their military presence in Germany.
In the 1970s, several TRC-97s were turned over to Air National Guard bases stateside.
The 5th Tactical Control Group based at Clark Air Force base in the Philippines used the TRC-97 extensively. The 5th TAC's mission was augmentation manning of SEA (Southeast Asia) radar installations. Many, if not most, of those missions were performed via TDY (temporary duty) support to Korea, Vietnam and surrounding areas during the Vietnam conflict. Most of these microwave links were used to provide communication links between the radar sites and the aircraft bases.
