Welcome back to another edition of ‘in their own (code) words’ wherein we look at the words of the world’s spymasters. I’m looking at Allen Dulles’ rather stolid The Craft of Intelligence, written in 1963. Dulles (1893-1969) had a long and storied career in intelligence, including a role as the first civilian director of the Central Intelligence Agency.
Today’s excerpt deals with the tracking of illegal radio operators. It’s interesting to recognize how much the technology available to assets and officers has changed, and to wonder how much things like cellphones have affected the game.
Counterintelligence, like most branches of intelligence work, has many technical resources, and one among them has been responsible in the past for uncovering more concealed intelligence networks than any other single measure. This is the interception and locating of illegal radio transmitters, known as “direction-finding,” or D/Fing for short. It employs sensitive electronic which, when mounted on mobile receivers, in a car or truck, can track down the location of a radio signal by indicating whether the signal is getting stronger or weaker as a mobile receiver weaves around a city listening to what has already been identified as an illegal transmitter.
Every legal radio transmitter, commercial or amateur, in most countries today is licensed and registered. In this country the call signal and the exact location of the transmitter are on record with the Federal Communications Commission. The FCC monitors the air waves at all times as a law-enforcement procedure. This leads to the uncovering of enthusiastic “ham” radio operators who haven’t bothered to get a license. It also leads to the discovery of illegal agent transmitters. The latter are usually identifiable because their messages are enciphered and they do not use any call signal on record.
Monitoring of a suspicious signal may also reveal that the operator has some kind of fixed schedule for going on the air, and this almost unfailingly points to the fact that he is transmitting to a foreign headquarters by prearrangement. At this point the D/Fing process begins. The main difficulty of tracking is that the illegal operator stays on the air, for obvious reasons, only for very short periods. As the mobile D/F experts try to trace his signal across a large city on air waves crowded with other signals, he suddenly finishes, goes off the air, and there is nothing the D/Fers can do until he comes on again some days or weeks later. If the Soviets are behind the operation, the transmission schedule, while fixed, may follow a pattern that is not easy to spot. Also, the transmitting frequency may change from time to time. The only solution is for the D/F headquarters to listen for the suspicious signal all the time and keep after it. But here, too, the technicians have invented new improvements to foil and outwit each other. The latest is a high-speed method of transmission. The operator does not sit at his telegraph key sending as fast as he can. He prerecords his message on tape, then plays the tape over the air at breakneck speed, too fast for any ear to disentangle. His receiving station at home records the transmission and can replay it at a tempo which is intelligible. If the illegal operator is on the air for only twenty or thirty seconds, the D/Fers are not going to get very far in their attempt to pinpoint the physical location of the transmitter.
This post first appeared on the Mister 8 Website, December 2009.