UA9CDC added:
Another dimension to this skimming thing is spotting on wrong
frequencies. Or the wrong band. Take the RBN data for a day - a
non-weekend day is better, as few stations actually on >1 band at
once then - and look for the same call spotted say 3 kc or more from
others at exactly the same time.
Open that window to a more realistic minute or two & see just how
many there are!
Every contest I run into several stations on CW who actually transmitt
3 signals. Main signal is usually 59+30 or more and two side bands
spaced 1-2 kHz from the main can be as loud as 59.
No wonder, close by skimmers decode then on these sideband frequencies.
That doesn't surprise me, given all the fecal signals I see on the bands
in my reincarnation as an SWL.
Though what I was referring to are skimmers reporting signals on
frequencies that the signals are not really on.
How many wrong frequency spots are there on RBN? Well, back when I was
looking for just same-call-different-band &
spotted-on-exactly-the-same-second, I found 140 such spots in a day (out
of 120k).
Open that window up to ~1.4 minutes & there were ~3700 spots of the same
call on a different band than other skimmers had spotted it on (and
probably more, as that excludes all spots of calls that might be on >1
band at the same time [DXpeditions, special event stations, etc]).
Of those 3700 same-call-different-band spots, about 100 were for
UA9CDC. UA9CDC very likely only operating on one frequency during the
~1.4 minute period concerned. Where UA9CDC was said to be:
20m: 14042.2, 14042.3
15m: 21039.9, 21040, 21040.1
10m: 28041.9, 28042, 28042.1
There are a number of mechanisms involved & it isn't just the poorly
implemented but popular quadrature sampling detector-based receivers
that do this.
73, ex-VR2BG/p.
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