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Date: Thu, 19 Jan 2012 15:23:05 +0000
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From: Andy Talbot <andy.g4jnt@gmail.com>
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Opera speeds
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Not true - the way its reported.

S/N is always (in amateur circles) referred to 2.5kHz.  So although
OP32 has 6dB lower bandwidth than OP8 (0.12Hz compared with 0.5Hz
signalling)   by teh time it is normalised to 2500Hz the figures end
up the same


Quite why, since WSJT introduced the idea, we chose to refer to S/N in
2500Hz is lost in the shrouds of time.  Just becasuse its about the
same as an SSB filter
Why couldn't we have done what the rest of the RF world does and use a
1Hz reference?

Andy
G4JNT


> Reports on my signals from PA0A, PA0AM, G4WGT and F6CNI (between 257
> and 465km) show variable results. The slower speed never produced a
> worse S/N, though sometimes it was exactly the same. Usually the
> result was between 4 and 9dB improvement with the slower speed.
>
> Intuitively, I would assume a 6dB improvement (though I am no digital
> expert), but occasionally better iif QRM is present as I would expect
> this to affect the faster signal more. Is this a reasonable
>