[Laser] Re: RTTY over light, anyone tried it?

[Garnier Yves]

Art
To minimise the sound card noise effect is rather
simple.
When you try to detect a weak useful signal hidden in
the noise, the sound card input must always be fitted
with a previously amplified input just under the ADC
dynamic saturation limit.
The sound card own input noise becomes then fully
negligible.
However I noticed that "spectrum Lab" seems a little
bit less sensitive and sound card type depending than
other programs like Spectran or Argo on very weak
signals even with the use of very similar FFT
parameters and I do not know exactly why...
 
73 Yves

--- Art <KY1K at verizon.net> a écrit :

> I've never done any form of listening, except for
> weak signals using 
> FFT and looking for the signature frequency using
> spectrum Lab.
> 
> But, I notice quite a few are using soundcards for
> various modes, 
> some for weak signals, some for moderately loud
> signal modes.
> 
> One topic that seems to be missing in this (and
> other threads) is the 
> soundcards input noise level. All soundcards are not
> created equal 
> and some are just barely worthy of playing the
> windows sounds when 
> the computer boots up.
> 
> The SDR, softrock and Flex-Radio people have done
> extensive research 
> into soundcards and the differences between the
> noise associated with 
> the input of the soundcard varies widely.
> 
> Anyone who is doing weak signal work with soundcards
> should be wary 
> of the AC97 integrated sound card chip set, which is
> absolutely 
> horrible. Sound Blaster sound cards claim 24 bit
> sampling, but the 
> first 10 bits are totally dominated by noise built
> into the card 
> itself, so it is no better than a 16 bit soundcard
> due to Mickey 
> Mouse electronics used on the card itself.
> 
> The best 24 bit soundcards are pricey and perhaps
> don't fit within 
> most laser users budgets. But, there are a few
> models that work 
> extremely well and are not expensive.
> 
> Other issues that degrade the performance for weak
> signal modes are 
> the lack of a balanced input (ground loop problems)
> which are a 
> significant issue that many seem to be totally
> unaware of.
> 
> Keep dem laser lit and enjoy. But, do be aware that
> what you do not 
> know about your soundcard can hurt you.
> 
> Regards,
> 
> Art
> 
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Yves F1AVY
http://pageperso.aol.fr/yvesf1avy/