## 2017-05-22

### Monitoring of HF Beacons by the Reverse Beacon Network: One-Year Spans

I previously posted graphs showing the signal strengths of the most-frequently-reported signals from HF beacon stations, covering the period from the inception of the Reverse Beacon Network ("RBN") in 2009 to the end of 2016.

Naturally, similar plots can be created for arbitrary periods, and such plots might contain interesting features other those on the long-term plots. Here I show plots covering 2016; similar annual plots covering the entire period from 2009 to 2016 are available here (the file has the MD5 checksum d868a05ff2945c0eefe81b68f1d0c301).

As before, each point on the plots covers one one-hundredth of the total span, or, in this case, roughly three and a half days. Also as before, for the period covered by each plot we first determine what qualifies as one of the top twenty beacons reported by the RBN, and, then for each such beacon, which ten RBN posting stations have spotted the beacon the largest number of times  over the duration of the plot.

I repeat the description from my prior post, with suitable emendations consistent with the change in domain:

1. Every spot by each of the ten RBN stations is plotted with a small open white circle (for the most part the individual circles aren't very obvious, as they overlap so much);
2. The ordinate for each of the strip charts ranges between 0 dB and the value shown as FSD (i.e., full scale deflection) near the bottom right-hand corner.
3. The value plotted in this manner is the value denoted SNR by the RBN.  Remember that the RBN has an odd definition of SNR.
4. The abscissa is divided into a number of bins of equal duration. In the plots on this page there are 100 such bins; because the duration covered by each plot is one year, each bin therefore covers about three and a half days.
5. At the bottom of each strip chart is a coloured bar. Each bin is coloured so as to represent the total number of times that the RBN station spotted the beacon in the period covered by the bin
6. For the period covered by each bin, a small purple rectangle represents the median value of the SNR over the duration of the bin.
7. Also for the period covered by each bin, the inter-quartile range of the SNR at each RBN station is indicated by a short vertical blue line.
8. The vertical order of the various RBN stations is determined solely by the chronological order in which each station first spotted the beacon.

As before, I note:
1. Frequencies are rounded to the nearest kHz;
2. The two graphs for I1MMR represent reception of a single station, which appears to transmit on 7026.5 kHz;
3. I am unsure how the U.S. stations in the list can be legal, at least to the extent that the transmissions were unattended, as §97.203 of the FCC's regulations appear to limit unattended CW HF beacons to a portion of 10m;
4. §97.119 of the FCC regulations appear to disallow the use of the "/B" indicator as used by the station signing W0ERE/B, as the B series is allocated to China.
5. It is my memory that the original HF beacons were all located on 28 MHz, so that listeners could be made aware of an opening. It is noticeable that not a single one of the stations on the list above is on 10m: the vast majority are on bands that can reasonably be expected to support some kind of non-local propagation at almost all times (which is probably the very reason that they are posted by the RBN so often -- but one does wonder what the putative purpose of such a beacon is).