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Date: Sat, 24 Jan 2009 21:28:26 +0000
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From: Andy Talbot <andy.g4jnt@googlemail.com>
To: rsgb_lf_group@blacksheep.org
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Subject: LF: Grabbers
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With this talk of grabbers, I'm surprised no one saw my experimental
SMT Hell Tx earlier this evening (around 1830 - 2000) on G3YXM's
grabber.
Having resurrected the code for a direct DDS driver that had been used
quite a lot on 73kHz a decade ago, I was experimenting with
bandwidths, pixel durations and fonts that would print well on that
grabber.

The best combination seemed to be 400 - 800Hz total frequency width,
with a horizontal pixel spacing of 0.1 to 0.3s and a thin (raster
type) font.  I'll probably be on again tomorrow, unless there's so
much activity this wide signal would cause QRM.

Not sure its a particularly good mode for weak signals though.  On
73kHz I was using very narrow shifts (5 - 20Hz wide) and testing it
against SlowCW modes. Seem to recall the consensus was divided on
which was more useful.  Could go narrower, but the grabber couldn't be
used to resolve it.

It was interesting, though, that for all that time the two Eu beacons
around 505kHz showed stronger on that grabber than I did.  Possibly
just an illusion as my signal was spead out and the beacons were
concentrated on a single pixel.

Andy  G4JNT
www.g4jnt.com