This allows us to plot the signals from the beacons over the life (so far) of the RBN. For example:
This graph shows how the 4U1UN beacon on 14100 kHz has been received by the ten RBN stations that have spotted it the largest number of times. (As mentioned in earlier posts, RBN stations for which location data are not readily available from the RBN site are not included.)
To help understand this plot, some description is in order:
- Every spot by each of the ten RBN stations is plotted with a small open white circle (for the most part these aren't very obvious, since they overlap so much);
- 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; in this case, the maximum value of each strip is therefore 50 dB.
- The value plotted in this manner is the value denoted SNR by the RBN. Remember that the RBN has an odd definition of SNR.
- The abscissa is divided into a number of bins of equal duration. In this and the other plots on this page, there are 100 such bins; because the duration covered by each plot is eight years, each bin therefore covers about one month.
- 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. Thus, in this plot, the short red bar near the start of the strip for WZ7I indicates that WZ7I spotted the 14100 kHz 4U1UN beacon about 3,000 times in the course of that month.
- For the period covered by each bin, a small purple rectangle represents the median value of the SNR over the duration of the bin. Thus, we can see that the median values for this beacon as recorded by SK3W consistently declined throughout the latter half of 2014.
- 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. Thus we can see that the inter-quartile range of signal strength at W3OA is consistently greater than the inter-quartile range at WZ7I and DJ9IE.
- The vertical order of the various RBN stations is determined solely by the chronological order in which each station first spotted the beacon.
There is (obviously) a lot to see on these plots.