Lev Theremin and the Music of the Ether (Part II)

Lev Theremin's skill at invention was not lost on the Soviet machine. Not long after his musical instrument was patented, the radio watchman security device it was based on started being employed to guard the treasures of gold and silver Lenin had plundered from church and clergy. The watchman was also being used to protect the state bank. Setting up and installing these early electronic traps took him away from his primary interest in scientific research. Just as he was approaching the limits of his frustration his mentor at the Institute gave him a new problem to solve, that of "distance vision" or the transmission and reception of moving images over the airwaves. The embryonic idea for television was in the air at the time but no one had figured out how to make it a reality. The race was on and the Soviets wanted to be first to crack the puzzle.  
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Having researched the issue extensively in the published literature, Lev was ready to apply the powers of his mind towards a solution. In the Soviet Union parts weren't always readily available. Some were smuggled in, and others had to be scavenged from flea markets -the latter a process very familiar to radio junkies. By 1925 he had created a prototype from his junk box using a rotating disk with mirrors that directed light onto a photo cell. The received image had a resolution of sixteen lines, and it was possible to make out the shape of an object or person but not the identifiable details. Other inventors in Russia and abroad were also tackling the issue. Fine tuning the instrument over the next year he doubled the resolution to 32 lines and then, using interlaced scanning, to 64. Having created a rudimentary "Mechanism of Electric Distance Vision" he demonstrated the device and defended his thesis before students and faculty from the physics department at the Polytechnic Institute. Theremin had built the first functional television in Russia. 
    
After this period Lev embarked to Europe and then America where he lived for just over a decade engaging the public, generating interest in his musical instrument, and doing work with RCA. As Hitler gathered power he was anxious about the encroaching war and returned home to the Soviet Union in 1938. He barely had time to settle back in when he was sent to the Kolmya gold mines for enforced labor for the better part of a year. This was done as a way of breaking him, a fear tactic that could be held over his head if he didn't cooperate: do what we say or go back to the mines. The state had better uses for him. He was picked up by the police overlord Lavrenti Beria who sent him to work in a secret laboratory that was part of the Gulag camp system. One of his first jobs was to build a radio beacon whose signals would help track down missing submarines, aircraft and smuggled cargo.

With WWII winding to a close the Cold War was dawning and Russia was on the offensive, trying to extend its reach and gather intelligence on such lighthearted subjects as the building of atomic bombs. In their efforts at organized espionage the Soviets sifted for all the data they could get from foreign consulates. Having succeeded with his beacon Lev was given another assignment. This time the goal wasn't to track down cargo or vehicles but to intercept U.S. secrets from inside Spaso House, the residence of the U.S. Ambassador. Failure to do the bidding of his boss would mean a return to the mines. His boss had high demands for the specifications of the bug Lev was to plant. The proposed system could have no microphones and no wires and was to be encased in something that didn't draw attention to itself.
  
The bug ended up being put inside a wooden carving of the Great Seal of the United States and was delivered by a delegation of Soviet Pioneers (their version of Boy Scouts) on July 4, 1945. Deep inside this "gesture of friendship" was a miniature metal cylinder with a nine inch antenna tail. The device was passive and was not detected by the X-Rays used at Spaso house in their routine scans. It only activated when a microwave beam of 330 Mhz was directed at the seal from a nearby building. There was a metal plate inside the cylinder that when hit with the beam resonated as a tuned circuit. Below the beak of the eagle the wood was thin enough to act as a diaphragm and the vibrations from it caused fluctuations in the capacitance between the plate and the diaphragm creating a microphone. The modulations this produced were picked up by the antenna and then transmitted out to the receiver at a Soviet listening post. Using this judiciously the Soviets were able to gain intelligence to aid them in a number of strategic decisions. The Great Seal bug is considered to be a grandfather to RFID technology.    

This wasn't the last time Lev was asked to develop wireless eavesdropping technology. For the next job his overseers upped the ante on him. No device could be planted in the site targeted for surveillance. The operation was code named Snowstorm. Lev used his interest in optics to figure out a method. Knowing that window panes in a room vibrate slightly when people talked he needed a method to detect and read the vibrations from a distance. Resonating glass contains many simultaneous harmonics and it would be a difficult to find the place of least distortion to get a voice signal from. Then there was the obstacle of reinterpreting the signal back into a speech pattern. Using an infrared beam focused on the optimum spot and catching its reflection back in an interferometer with a photo element he was able to pick up communications. Back at his monitoring post he used his equipment and skills to reduce the large amounts of noise from the signal.   
A few years later Lev was released from his duties at the lab, but was kept on a tight leash and not allowed to leave Moscow.

HOW TO BUILD A THEREMIN FROM THREE AM RADIOS 
    
For those amateurs wishing to build and play a theremin there are many commercial kits available on the market. However a simple theremin can be built using just three AM radios. If you don't already have these laying around the house they can easily be obtained from your local thrift store.

One of the radios will be a fixed transmitter, another a variable transmitter and the third would be the receiver. The volume knobs on the fixed and variable transmitters can be turned all the way down, as they are just used to produce the intermediate frequency oscillations that will be picked up by the receiver. The receiver radio should be set on an unused frequency in the upper range of the AM band such as 1500 Khz. If it is in use tune to a nearby space where only static is heard. The fixed and variable transmitters should then be tuned 455 Khz below where your receiver is set, in this example 1045 Khz. 455 Khz is a common difference in the local oscillator frequency, although there can be variations. As these frequencies are set the receiver should start to make a whistling type sound, the production of a beat frequency.

The next step is to open up the variable radio and look for the variable capacitor, often housed in white plastic with four screws. Find the terminal that takes the station out of tune and use an aligator clip attached to the antenna, or solder a wire from the antenna to the oscillator terminal. Now the controls will have to be adjusted slightly again. Tune the fixed transmitter until the receiver starts whistling and have fun playing with the sounds it creates.          

Sources:
Theremin: Ether Music and Espionage by Albert Glinsky, University of Illinois Press, 2000
https://en.wikipedia.org/wiki/Leon_Theremin
How to Make a Basic Theremin by eltunene: https://app.box.com/s/kgdstzwaoc/1/17284427/181802859/1