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Re: LF: DFCW, an idea.

To: [email protected]
Subject: Re: LF: DFCW, an idea.
From: "Rye Gewalt" <[email protected]>
Date: Tue, 17 Apr 2001 05:55:33 -0400
References: <[email protected]>
Reply-to: [email protected]
Sender: <[email protected]>
Great Idea, I have been thinking along the same lines.  There are programs that allow the PC clock to be set within about a second to National Standards using the internet.  The PC clock could be set at the start of a transmission and then there could be a window within the bauds to do the FFT(s)  --- drop a couple of seconds on each end of the baud.  I am a great fan of signal averaging.

I'll try to find the software for synchronizing the PC clock with our Naval Observatory and send you a link.  It's pretty nice and even tells how far your clock was off prior to calibration.  There is some magic I don't understand about the network delays, but apparently they have that pretty well solved.


Laurie Mayhead wrote:

Hi all,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. Looking at the signal on my monitor (also see Uwe's pics,thanks Uwe) these gaps are still poorly defined. I have thought about synchronising the Tx and Rx using some form of universal time signal but 1) this might be thought as cheatingand 2) the path variations, phase changes etc would be a problem. 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 ?   73s Laurie.
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