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From: "Andy" <actalbot@southsurf.com>
To: rsgb_lf_group@blacksheep.org
Date: Tue, 31 Jan 2006 16:21:02 -0000
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Subject: Re: LF: T/A JAN 31
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A professional programmer who spent somef time working on waterfall palettes
for signal analysis once suggested that, it order to see signals separated
from the background by only a small amount, a waterfall should change
brightness rapidly and colour more slowly, even if some brightness levels
repeat over the dynamic range.  Working on the basis that most interest is
in weak signal resolution, and stong ones can be left to fend for
themselves,  he suggested a palette that ran from dark blue, through red to
yellow then back via green and orange to black.  (Or other  variants like
this) .  A bit weird but brightness as perceived by the eye is then peaked
part way up the signal range.

The dark blue could then be placed at the noise level, so the normal noise
spikes averaging 2 - 4dB above mean, say, would push towards red (also a
dark colour), but signals at 6 - 10dB S/N would show clearly as bright
centre optical-spectrum green/yellow.   Really strong sigs would be
orange/black but would not be hidden as they'd have brightly coloured
sidebands making them stand out against their own background.  I never tried
it - but may do now the idea has been awakened.

Andy   G4JNT
www.scrbg.org/g4jnt/


>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.