From: "M. Sanders" <misan@xs4all.nl>
To: rsgb_lf_group@blacksheep.org
Subject: LF: RE: Spectrogram query
Date: Wed, 28 Jul 1999 01:43:26 +0200
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Dear John and Lowfers,

Last weekend I was still using 5.01 but i have tried to look at Finbar,
EI0CF's signal this morning and made a recording with 5.08. I used the same
settings in 5.08 as in 5.01. There are some improvements in the new version
but changing the settings dit not give better results. I could see a signal
going slowly up and down a few Herz around 136.150, may be a VFO/TX but
nothing audible (may be QRS CW ID for beacons is an improvement?). The Loran
lines where perfectly visible as well as natural radio signalas running
diagonally downward on the screen.  DSP processing of the WAV recordings did
not provide a positive ID on Finbar's call sign so I am still in the dark.
The settings are listed on my site at:
http://www.xs4all.nl/~misan/gram50+2.htm.

By choosing colours in three bands the eye can separate the signals into10dB
bands with 2.5dB brightness levels. This helps identifying signals. The
general idea is to give stronger signals in a 10 dB band a lighter colour.

The traditional rainbow spectrum and the shaded grey or blue spectrums
represent exactly the same information but I look at it like fishing in a
pond. The strong signals have red to yellow colours and can be compared to
ducks floating on top of the water. The blue lines represent a relative
signal bandwith -40 to -50dB. This band acts like the water surface. I
adjust the gain so all Loran-C lines show as blue dotted lines with a few
red dots in the peaks. The green bands are signals with a relative
strenght -50 to -60 dB. When listening to a WAV file recording it is
interesting to change the blue colours temporarily in to black. The reslult
is like putting on sunglasses and then looking at the fishes down on the
bottom of the pond without light reflections and ripples from the surface
obscuring the sight. The spectogram on my site from DF3LP's signals show him
to be a 'fat-duck' (his signal is audible 10dB or more above noise level!).
Toni, HB9ASB's signals are slightly above the noise level. To show his call
sign better in the picture the gain was increased and thus shifting the
spectrum to red/yellow.

When AGC is turned on the average level can be stabilised between light blue
and vivid red.  Loran-lines look now like thin and straight lines. When
there is fading (QSB) wtihin de AGC range the signals do not change their
colour making it easier to keep track one perticular signal. For DX
'fishing' and when listening close to strong signals no AGC should be used
of course.

Best 73's and good luck on LF,

Michael Sanders, PA3BSH
mailto:pa3bsh@amsat.org


> -----Oorspronkelijk bericht-----
> Van: majordom@post.thorcom.com [mailto:majordom@post.thorcom.com]namens
> wireless
> Verzonden: dinsdag 27 juli 1999 19:53
> Aan: rsgb_lf_group@blacksheep.org
> Onderwerp: LF: Spectrogram query
>
>
> No one came back on my Spectrogram comment yesterday - does
> anyone use 5.08
> and what settings have you found best for 10 sec dots?
>
> 73
> John Taylor  G0AKN
> earth@wireless.freeserve.co.uk
>
>
>
>
>