What did the EC-121R "Batcat" aircraft do in Vietnam?

The EC-121Rs deployed in Vietnam were known as "Bat Cats." For a brief period they monitored the sensor fields on the Ho Chi Minh Trail and also operated as communications relay aircraft. The sensor transmitters sent their data to an orbiting EC-121R of the 553rd Reconnaissance Wing, based at Korat Royal Thai Air Force Base. Special receivers installed in those 553rd Reconnaissance Wing aircraft were responsible for picking up the signals.

When the aircraft was within range, it automatically relayed the collected signals to the Infiltration Center. That relay was carried out via a radio link in the 2200 to 2300 MHz band to Nakhon Phanom. The information gathered could be sent to the Task Force Alpha center at Nakhon Phanom or analyzed on board by the mission crew, made up of radio and electronics specialists. What was received was used to direct air strikes against stretches of the trail known to be active.

Each aircraft orbited over South Vietnam, Laos or even North Vietnam for about eight hours, while a seven-person combat information crew monitored the radio transmissions from the air-dropped sensors. A retired EC-121R Batcat was preserved at AMARC at Davis-Monthan Air Force Base, Arizona.