I started the ARRL Frequency Measuring Tests in April 2018. This is my fourth effort and I’m delighted that I made the green box — measures within 1 Hz.
- 80 meters — +0.54 Hz off
- 40 meters — 0.00 Hz right on the mark
As with past FMT’s I used my Icom IC-9100 as the receiver, connected to a Cushcraft MA6V. That’s not the best antenna for 80m and 40m, but it gets the job done.
I also use WSJT-X and the Frequency Calibration mode. For the calibration stations I used a couple of local broadcast stations, WWV at 2.5, 5, and 10 MHz, and CHU at 3.33 MHz. I could have included WWV at 15 MHz but I didn’t want that to somehow skew the results since the measurements were at 3.5 and 7 MHz. I also decided to do the calibration two hours before the measurements.
After each measurement, I copy and paste the measures to a text file, import it to a spreadsheet, and then select the range of measurement with key down. I also try to delete any suspect measures either based on signal-to-noise or signal levels. This time, I compared the before and after of my tweaking and didn’t really find much difference. I also graphed the results of the “difference frequency” measures.
There are certainly some challenges around the 7 MHz measures, even though the measurement average was exactly on the mark. It is also interesting to see the slope of the measures at 3.5 MHz, resulting in an average that was +0.54 Hz off the mark. My measures at the beginning of the key down period were closer than the average.
You can find out more at this website http://fmt.arrl.org/
