Spycraft - Melton [112]
Concealments were a mainstay of the OTS laboratory. On his initial visit to the lab, a newly appointed office director commented on the variety of high-quality woods that were in the inventory.
An OTS craftsman pointed to a piece of lumber and asked, “What do you see?”
“Cabinet-grade walnut,” replied the director with pride in his knowledge of woods.
“No, sir,” corrected the concealment specialist, “that is volume in a cellulose wrapping. And we can put anything we choose underneath the wrapping as long as it doesn’t exceed the volume.”
Once the “volume” of the bug package, consisting of microphone, transmitter, switch receiver, power cells, and antenna were reduced to six cubic inches or less, relatively small blocks of wood could encase all the system’s components. The wood block became the workhorse for “quick plant” audio operations. “RF transparent” wood could be cut into almost any configuration with hand tools and then screwed, bolted, glued, or wedged into place. Small blocks could be fashioned to blend in with furniture, the molding in an office, or a picture frame by matching wood types, grains, and finishes.
For twenty years after the introduction of the SRT-3, each successive SRT model saw either the size of the transmitters decrease or improvements in performance or security.2 Transmitter models in the mid-1960s also marked the introduction of signal masking systems to defeat audio countermeasures. Without masking, a technical sweep team could inspect a facility with electronic and magnetic equipment that scanned the RF signal spectrum and detected foreign objects to locate, lock onto, and expose the secret audio transmissions. Masking reduced the vulnerability of bugs by making their signal harder to isolate and identify as clandestine transmissions.
One masking technique commonly used by both the United States and Soviets buried the transmission in the signal’s subcarrier. RF transmissions were designed to broadcast in two parts, much like stereo. The first part, a clear signal resembling white noise, was passed over as benign by someone scanning the radio spectrum. Then, just to the left or to the right on the dial—up or down the spectrum—was the subcarrier with the clandestine message. By tuning to the right frequency and tuning out the white noise, it was possible to hear the covert transmission. In principle, the use of subcarriers worked like hiding a piece of clear glass in a container of water. The glass remains invisible until the water is drained.
Other techniques for using subcarriers sent the audio signal along the existing AC power lines where it was collected and retransmitted to a listening post. Signals could be encrypted, masked, or both.
True to the nature of espionage, each technological advance was inevitably met by an effective countermeasure. In time, KGB counterintelligence teams began tuning in on the white noise in search of subcarrier transmissions. OTS responded and advanced the technology to the next level. “Concealing signals was an area I felt very strongly about,” said an OTS manager who oversaw the program. “I wanted to come up with new modulation schemes, every year I wanted at least four or five brand-new ones to hide our transmissions. For a while we got into a pattern of using certain types of subcarriers almost exclusively and, unfortunately, the Russians knew what to look for in our ‘offsets.’”
Eventually these techniques of hiding transmissions came to include a frequency-hopping technique in which short transmission bursts bounced up and down the radio spectrum in no apparent order. Without a receiver coordinated to the changes in transmissions, these frequency hops proved particularly difficult to identify and intercept since it was nearly impossible for sweep teams to anticipate the signal’s pattern.
The complexities and opportunities presented by clandestine audio seemed endless. Installing an audio bug always put the techs at personal risk of discovery and arrest when entering, leaving, or working at a target. Building