[TowerTalk] Activity by Mode was: Re: Fwd: MFJ QRT on May 17, 2024

[Joe Subich, W4TV]

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
>