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Re: LF: DFCW, an idea.

To: [email protected]
Subject: Re: LF: DFCW, an idea.
From: "Mike Dennison" <[email protected]>
Date: Thu, 26 Apr 2001 11:04:12 +0100
In-reply-to: <[email protected]>
Reply-to: [email protected]
Sender: <[email protected]>
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



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