Envelope-to: dave@picks.force9.co.uk
Delivery-date: Tue, 24 May 2005 14:08:15 +0100
From: "james moritz" <j.r.moritz@herts.ac.uk>
To: rsgb_lf_group@blacksheep.org
Date: Tue, 24 May 2005 13:51:23 +0100
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Subject: LF: RE: reception with multiple antennas
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Dear Stewart, LF Group,

I think this is a very interesting propagation experiment, apart from
potentially being able to enhance reception, so really ought to be tried. As
you say, there has been speculation about LF "beam-forming" on and off for
ages - I'm a bit sceptical about the extent to which the ionosphere will be
prepared to co-operate, but it would certainly be interesting to find out
the kind of separation between antennas that could be used for coherently
processing the signals.

I guess for an initial feasibility study it would only be necessary for a
number of stations to simultaneously make recordings under defined
conditions, and then the data could be up-loaded and post-processed at
leisure. I have a few queries:

-I presume you would have to initially synchronise the recordings to within
a GRI period for the signals to be combined in this way - would this require
some external timing signal, or is it possible to obtain that info from the
Loran signals?

-how would you compensate for variations in gain between different receiving
stations?

-how would you deal with variations of phase response within the passbands
of different stations?

As to whether I would run it at my station, certainly. I guess a broadband,
"always on" internet connection would be a requirement, which at the moment
I don't have, but may well get soon.

Cheers, Jim Moritz
73 de M0BMU


-----Original Message-----
From: owner-rsgb_lf_group@blacksheep.org
[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Stewart Nelson
Sent: 24 May 2005 09:54
To: rsgb_lf_group@blacksheep.org
Subject: LF: reception with multiple antennas

Hi all,

I've been dreaming about a system tentatively named MARS (Multi
Antenna Reception System)....