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Re: LF: Narrow B/W Techniques

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Subject: Re: LF: Narrow B/W Techniques
From: Wolf DL4YHF <[email protected]>
Date: Tue, 05 Jul 2005 20:51:59 +0200
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Hi Laurie,

It shouldn't be too difficult to implement such a synchronisation - though I am not really convinced how 3 dB can be gained from this. One must consider that the usual "waterfall" software scrolls a bit faster than a "dot" interval, accepting some smearing, but sometimes this improves visibility. In Spectrum Lab there is the option "triggered spectrogram", which was used in an experimental chirped radar once. If you feed a 1-pulse-per-second signal to one of the inputs of the soundcard, you can already synchonize the waterfall display to that signal. The problem with the windows system clock is (at least under Win XP) that it drifts like hell, for absolutely obscure reasons, if its not permanently corrected by Dimension4 or the like. Too bad ! The battery-buffered "CMOS clock" in my old 486 machine was off by a few seconds per month - and easy to read under DOS - but these days it is almost impossible to access the CMOS clock registers directly without some low-level kernel driver programming. A similar kind of "external" sync could be achieved with QRSS-sending software too. The question is still, will it pay out if the spectrogram is decoded by eye/brain .
Best regards,
Wolf  DL4YHF.

P.S: Thanks for the nice CW contact last weekend. Hope it's not one of the last, thinking about the new Loran TX.....



Lawrence Mayhead G3AQC schrieb:

This is an appeal to the writers of QRSS/Argo?Spectran software, and also to those much more expert than I am to comment.
Is it time we looked at method of time synchronisation? in order to
improve sig/noise ratio in very slow morse transmissions. ie QRSS.
As I understand it about 3db improvement is possible by making the FFT
sample time equal to the dot length.
If we are using QRSS10 for example a time accuracy of 1 sec. is only
10% and at QRSS30 this is only a 3% error. I should not have thought
it too difficult to get this fromGPS or even MSF-60 or DCF 77 time
clocks, nor should it be too expensive.
My big question is however how do I :- 1) Synchronise my QRSS/DFCW
programs and 2) my Spectran/ARGO programs to the computer clock. Does
this facility exist and if not would it be very difficult to implement?

If these options were available perhaps more people would consider
locking their computer clocks, so perhaps we could win another 3db.

73 Laurie


Whatever you Wanadoo <http://www.wanadoo.co.uk/time/>

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