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Re: [TowerTalk] Funniest thing I've seen in weeks

To: "Tom Rauch" <>,"Jim Smith" <>,"towertalk reflector" <>
Subject: Re: [TowerTalk] Funniest thing I've seen in weeks
From: "Jim Lux" <>
Date: Mon, 11 Oct 2004 08:38:15 -0700
List-post: <>
> I'm a big fan of diversity receiving systems.
> I use stereo. I use spatial diversity on 160 and 80 meters
> because I only have vertically polarized antennas with good
> directivity on those bands.

This is a very popular technique... (it's simple, and makes use of that
wonderful signal processor between your ears)

> On 40M I can use either spatial or polarization diversity.
> My antennas are here:
> I don't know what 20 and higher are. I don't work them much,
> but when I do signals are like on a telephone.
> On 160 meters, I need about 2000 feet spacing to get good
> diversity. On bands where I can do both polarization and
> spatial diversity, like 40, I find spatial works better than
> polarization diversity.

The researchers who are studying this (they're in France, I can't recall the
names off hand) find that even with identical real antennas in real
locations will have different polarization characteristics, and that it's
the combination of pattern and polarization diversity that really makes
things work.
> The largest effect I hear isn't a reduction of QSB. It is
> the fact noise takes a hollow sound and signals are easier
> to pull out when near noise floor. Signals that are only
> occasional letters and beeps on either channel become
> perfectly readable in stereo.
> I've found this requires the receivers for each channel be
> PERFECTLY phase locked and have nearly identical
> characteristics for maximum effect.

If you're combining "post detection" (not sure where that would be for SSB)
then phase locked shouldn't be a huge issue (although, with stereo, the
phase information would manifest itself as a apparent change in audio
direction of arrival).  Frequency matching would be important (particularly
for sideband.. probably less so for CW... after all there are widgets that
spread the band out acoustically based on frequency)


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