What's the Frequency, Kenneth?

Early in my career, I got a job as a contract engineer for a local radio station. The station's assigned frequency was 1.000 MHz, and the transmitter was a Gates BC-1T, which was probably the best transmitter ever built for AM broadcasting. The crystal was cut for maximum stability over time and temperature and then sealed in a vacuum. The overall stability was better than one part per million (ppm).

In those days, the operator was required to check the frequency every half hour or so because when the regulations were written, crystals were far less stable. At the transmitter site was a General Radio frequency meter that showed deviation from the assigned frequency. Once a month, the frequency had to be checked against the National Bureau of Standards. Most stations contracted an outside company to conduct that test.

Because of the stability of the transmitter, the logs showed every frequency reading to be zero. Since the operator was in the studio, miles from the transmitter, for all he knew, the meter could have been turned off. The engineer who preceded me readjusted the transmitter so that it was two Hertz high and then the operator recorded rows and rows of "2" in the frequency column. The FCC required that the frequency be within plus or minus 20 Hertz of the assigned frequency.

During the time I was the contract engineer, the requirement to measure frequency was eliminated, and I typically checked the frequency each week when I calibrated the meters. I also reviewed the report from the company that checked our frequency, and each month the report said 1000002 Hertz. Since the transmitter was well within the regulations, I saw no reason to readjust it. "If it ain't broke, don't fix it!"

Years after leaving the station, I learned that some companies in the area, including the Army base, used our station as a frequency standard, rather than WWV, which can only be received at night to calibrate signal generators, frequency counters, and other equipment. I got a sick feeling because it meant that everything that came out of those companies and the Army base were 2 ppm high in frequency.

This entry was submitted by Frank Karkota and edited by Rob Spiegel.

Frank Karkota worked with power transmitters in the range of less than 1 MHz to 5 GHz. He designed and built equipment for radio stations and eventually started a company that made commercial and consumer receivers that covered 500 kHz to almost 1 GHz.

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