KC4VZT's frequency fingerprint

15 posts / 0 new
Last post
VE7DES's picture
Last seen: 1 week 4 days ago
Joined: 2013/12/23 - 23:51
KC4VZT's frequency fingerprint

I present this graph (.PNG) for KC4VZT's interest. His new 100mW beacon is performing well and is even being heard in Europe at SNR approaching -15 dB.

The frequency being reported does vary. The extremes I found fall inside a >200 Hz range, 14.096994 to 14.097210 MHz. This is wider than the WSPR band itself.

Of course this degree of scatter is due to the reporter's drift combined with the beacon's. How do we tell if the beacon is drifting for real, or just the reporters?

I obtained 1148 reports from the old database interface and sorted them, first by reporter, then by frequency. Then I graphed this data with OpenOffice, tweaking the format until I saw something I liked.

The "sawtooth" appearance was arrived at by accident and is rather informative. The prominent "teeth" are the spots from the most productive reporters. The X-width of each "tooth" varies because each reporter has uploaded a different number of spots. But all the "teeth" are basically straight ramps, with a slight excess at the higher end, and the shapes and Y-amplitudes are pretty consistent.

So the beacon is drifting in a 150 Hz range with a fairly uniform distribution.

This range is about 10 ppm. For comparison, I used to work (and hard!) to get UHF mobile radio crystals compensated for +/-5ppm over -30/+60C. My WSPR beacon, an old Icom transceiver, drifted 1 ppm in my living room which faced the sun. Newer rigs maintain considerably better than 1 ppm in temperature ranges typical of ham shacks. On 20m, I find most SSB ops tend to "channelize" themselves at 1 kHz intervals with no more than 10 Hz of pitch error. --Except during contests, when the competitors seem to revert to the days of undisciplined dial VFOs.

My post is friendly. I draw no conclusions and intend no criticism of the beacon operator.

- Dan