Frequency measurement take a look at success doesn’t require refined gear

04/10/2019

On April 12, ARRL will conduct the Frequency Measurement Test (FMT), a tradition that dates back to 1931. During this time potential participants were promised “a pleasant and profitable experience” and it was advised that participation in the FMT would be a form of insurance against out-of-band operation “and the unpleasant consequences that follow.” Official observers and official relay stations had to attend the FMT or make a damn good excuse. W1MK – the predecessor of W1AW – was one of around a dozen broadcasting stations. The 80- and 40-meter frequencies were confirmed by an agreement with the radio division of the US Department of Commerce.

Accurate frequency measurement – at least to the extent that radio amateurs seldom worry about working outside of an amateur assignment – is now almost a matter of course. However, today’s FMT conductors can measure precisely beyond the number of decimal places (up to 5) that a typical transceiver displays. FMT announcements can evoke visions of a wide variety of sophisticated laboratory equipment. While some of the most successful stations had lab-quality equipment, others came pretty close with far less hardware.

FMTs take place in April and November. The FMT from November 2018 Results are available on the ARRL website. The actual frequencies were 3,598,726.31 kHz at 80 and 7,064,327.23 at 40.

Tom Wilheit, WX4TW, one of those who measured the 80- and 40-meter frequencies of the K5CM transmitter station to 1 Hz or less on Nov. 8, reported using an Elecraft KX3 transceiver and Spectrum Lab audio spectrum analysis software. Others took a similar approach. James Keeth, AF9A, reported with a “openHPSDR Mercury receiver, a 10 MHz OCXO reference calibrated against CHU and WWV, and the WSJT-X frequency mode for measurements. ”

Jim Michener, K9JM, relied on his Elecraft K3 and tuning forks to get off mark within 1 Hz on both bands. Grady Harper, AJ4YA, got very close to the signal from his K3 and adjusted the measured frequency to “correct errors in my tuner”.

“This is my first attempt at this type of adjustment,” said Harper. “The fraction of Hz is based on the amount of time between beats. I guessed that part. “

If you’ve never entered an FMT before, Connie Marshall, K5CM, offers information on his website how to measure the frequency of a carrier. Articles in QST have also covered this topic.

The April 2019 FMT will be launched on April 12 between 0200 and 0225 UTC. The 40 meter frequency is near 7065 kHz and the 80 meter frequency is near 3599 kHz. See page 94 of April QST for details.

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