From: "Mike Dennison" <mike.dennison@rsgb.org.uk>
To: rsgb_lf_group@blacksheep.org
Date: Thu, 26 Apr 2001 11:04:12 +0100
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Subject: Re: LF: DFCW, an idea.
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G3ACQ wrote:
> I am very keen on exploiting DFCW to its limit (after all its easy to implement)
> but it still needs to be speeded up. Because of the lack of timing of the FFT
> bins they tend to become blurred and it is neccessary to leave large gaps
> between elements of a character with consequent waste of time.This is even more
> true with QRSS. With DFCW the frequency change between dots and dashes
> adequately separates them. Currently on T/A tests I have been using a 50 sec.
> period, 30 secs constitutes the transmitted element and 20 secs the gap ! What a
> waste of time. [cut] So
> my point is WHY BOTHER ! would it not still be possible to read the message
> without these gaps (they are hardly there anyway). For A to Z there is not much
> of a problem since there are only two adjacent elements ie 2 dots or two dashes,
> except for JO S H .But the numbers are a bigger problem. Anyway, crazy perhaps
> but any ideas ?  

Not crazy at all, and some early DFCW transmissions had no gaps at all 
between elements. It was, however, rather difficult to read under practical 
conditions, so the small gap was reintroduced. An improvement might be 
made by being able to place an adjustable spacing grid over the spectrogram 
so that it is much clearer to see when elements should start and stop. This 
would give a practical advantage in noisy conditions, whilst being much easier 
to implement (at the user level) than time synchronisation. Is this practical in 
Argo or any of the other visual CW readers?


Mike, G3XDV (IO91VT)
http://www.lf.thersgb.net