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Date: Tue, 31 Jan 2006 15:34:10 +0100
From: Alberto di Bene <dibene@usa.net>
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Subject: Re: LF: T/A JAN 31
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Roelof Bakker wrote:
> 
> I have heard rumours that ARGO and SpecLab need some background noise to 
> compare the signals against and hence should work better with a (relative) 
> wider bandwidth.

Roelof,

   I don't know about Speclab, maybe Wolf will comment about it.
What Argo does is to convert signal strength to brightness on the screen not
in a way related to the absolute magnitude of the signal, but rather to the ratio
between it and the background noise, which is evaluated using the quartile
technique. The relation between magnitude and brightness is non linear, being
subject to a gamma stretching, similar in concept to the gamma correction
used in Photoshop or in Paint Shop Pro when dealing with pictures.
The Contrast slider just adjusts the value of gamma.
The plus side is a good sensitivity, as Alan pointed out. The drawback is that
an increase of the noise level (as during static crashes) affects also the
brightness level of the signal trace. I have some ideas (yet to be tested) on
how to overcome that, and maybe they will be implemented in the next overhaul
of Argo, as soon as another project will be completed.

73  Alberto  I2PHD