First-Hand:Radio Engineering and NACA Telemetering
Submitted by Paul Burk
As many other Life Members , I got into radio about 1929 via a catwhisker, a galena crystal, a pair of headphones and about fifty feet of antenna wire. The livingroom, bathroom and bedroom were wired for headphones from the single crystal sitting on the livingroom window sill. Subsequently, I advanced into vacuum tube radio by acquiring three discarded sets at the old Cortland Street (New York City) flea market.
At one time, I had a collection of GOA's, OlA's, 71A's, 99's, Kellogg bulb top connected heaters and other vintage items of that era. Typical of many youngsters of that time, I was into model planes and photography as well as radio. But since radio repairing was the only self supporting hobby, I stayed with it and have been with it ever since.
One of my most hilarious experiences was when I held the job of keeping the radios and record players working at the House Plan, a college sponsored social house. They had an early model RCA console with an automatic record changer that must have been designed by Rube Goldberg. After playing a record, the changer would literally toss the record into a side bin of the console. When things were not adjusted just right, the disc might go sailing over the edge of the cabinet and land anywhere.
Also, the console had electromagnetic twelve inch dynamic speakers with more field flux outside the housing than around the voice coil. So when people dropped the steel phonograph needles, they were sure to be found around the field coil. A raspy sound called for cleaning up the discarded needles.
I was stationed at Langley Field when WWII ended. Upon discharge, I was hired by the NACA Instrument Research Division. My first assignment was to miniaturize the existing 100 kc oscillators using proximity fuse tubes in the existing Franklin oscillator circuit, (a two stage resistance coupled L-C oscillator). After running some tests on this circuit, it became obvious that it was very unstable due to the "Miller Effect" which I announced as a passing remark to one of the other engineers. Well, all pandemonium broke out. What was "Miller Effect"? A mad scramble to some reference books followed.
When I assembled and calibrated this RM 1 telemeter, I had no idea what we would be discovering in that forthcoming flight at Wallops Island, off the coast of Virginia. The RM 1 was powered by two tandem cordite rockets and had fixed aileron settings to cause the missile to roll counter clockwise during its flight. It was tracked by 584 radar, fastax camera and four channels of telemetering, azimuth (roll), total head pressure, lateral and transverse acceleration.
The first record to be developed was the telemeter recording from the mirror galvanometers. As you might well imagine, all hell broke loose when our roll record indicated that the missile, which was rolling counter clockwise at takeoff up to about mach 8, reversed its roll and was rolling clockwise during transonic flight.
"Telemetering must have screwed up again, etc. etc." is all we heard until some time later when the fastax film came out of developing. It showed that the missile did in fact experience a reverse controllability. Consternation throughout resulted, especially from 'ole Marve Pitkin who was the project engineer on the RM 1. About a week later, the analytical group came up with the same result (but I still wonder if it was independent of our experimental data). Flash! At precisely this time, Chuck Yeager was at Edwards Air Force Base ready to take off in the Bell. A panic call went out to Edwards to call off the flight until the NACA group analyzed the data and determined a proper flight procedure for Chuck. Needless to say, the esteem of our telemetering group went up a few notches after this flight. Later that year, NACA telemetering was written up in the Congressional Record, (1946-47).
I installed the first FM police radio in Juarez about 1950, and about a year later a similar system on the same frequency in Chuahuahua City. Shortly after this installation, a gang of bank robbers in Juarez was making a high speed getaway heading south, ahead of the Juarez police who had no hope of catching them. So the Juarez dispatcher telephoned the Chuahuahua City police to send several radio patrol cars north to intercept the gang. About a half an hour out of the city, the two police forces were in contact with each other and was that gang surprised at the "friendly" greeting they got going and coming! The Juarez police chief felt that one job paid for the whole radio system.