On 4/29/2024 11:08 AM, Pete Smith N4ZR wrote:
> Looking at my own RBN node, I routinely spot CW signals with
> signal-to-noise ratios of as little as 4 dB. To be sure, FT8 is much
> better at signals below the threshold (I see -24 dB signals all the
> time), but 4 dB is pretty weak. So yes, there will be
> disproportionately more FT8 spots, but the RBN spots many relatively
> weak signals.
CW and FT8 spots/signal reports have completely different reference
levels. FT8 SNR is in a 2.7 KHz bandwidth while CW is in (maybe) a
100 Hz bandwidth. 20Log(2700/100) = 28(.6) dB ... the -24 dB FT8 spot
would be equivalent to a 4 dB CW spot!
73,
... Joe, W4TV
On 4/29/2024 11:08 AM, Pete Smith N4ZR wrote:
I suspect this thread should move to another reflector, but before it
does ... I don't want a few misconceptions to pass uncorrected.
Steve says "note how many timers a CW caller is spotted on RBN while
calling in a pileup." The answer, to the best of our ability, is NONE.
It does happen very occasionally when the timing between caller and the
called station's CQ is just right, and the caller is within 50 Hz of the
CQer, but that's it. Split callers are never spotted by the RBN.
Steve also asks "where are the RBN spots [in the CWTs?" The answer is,
there are TONS. I don't have a huge signal, yet I was spotted over 100
times in the last 10 minutes in the 19Z CWT last week. Yes, I was CQing.
Looking at my own RBN node, I routinely spot CW signals with
signal-to-noise ratios of as little as 4 dB. To be sure, FT8 is much
better at signals below the threshold (I see -24 dB signals all the
time), but 4 dB is pretty weak. So yes, there will be
disproportionately more FT8 spots, but the RBN spots many relatively
weak signals.
I'm not arguing that the RBN is directly, precisely comparable to other
tools for measuring activity, but it's what we have for CW.
73, Pete N4ZR
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