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OT: ARRL - FMT Success Does Not Require Sophisticated Equipment

N8FNR Member ✭✭
edited April 2019 in New Ideas
Some here may find this of interest.


On April 12, ARRL will conduct the Frequency Measuring Test (FMT), a tradition that dates back to 1931. In that era, prospective participants were promised “a pleasant and profitable experience” and advised that taking part 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 were required to participate in the FMT or offer a darn good excuse. W1MK — the predecessor to W1AW — was one of a dozen or so transmitting stations. The 80- and 40-meter frequencies were confirmed through an arrangement with the US Department of Commerce Radio Division.

Accurate frequency measurement — at least to the degree that radio amateurs rarely worry about operating outside of an amateur allocation — now is almost a given. But today’s FMT leaders are able to accurately measure beyond the number of decimal places (out to 5) a typical transceiver will display. FMT announcements may conjure visions of a vast array of sophisticated laboratory equipment. However, while some of the most successful stations did have laboratory-grade gear, others got quite close with far less hardware.

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

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

Jim Michener, K9JM, depended on his Elecraft K3 and tuning forks to get within 1 Hz of the mark on both bands. Grady Harper, AJ4YA, got extremely close by zero-beating the signal on his K3 and adjusting the measured frequency “to correct for errors in my tuner.”

“This is my first try with this type of adjustment,” Harper said. “The fractional part of the Hz is based on length of time between beats. I guessed at this part.”

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

The April 2019 FMT will get under way at 0200 – 0225 UTC on April 12. The 40-meter frequency will be in the vicinity of 7065 kHz, and the 80-meter frequency will be in the vicinity of 3599 kHz. Details are on page 94 of April QST. 

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