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Re: LF: EbNaut from Todmorden

To: rs[email protected]
Subject: Re: LF: EbNaut from Todmorden
From: Paul Nicholson <[email protected]>
Date: Mon, 14 Mar 2016 19:34:06 +0000
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Stefan and Markus, thanks very much for the reports!

A nice result from Heidelberg and you did a full phase search
in 15 degree steps!

I think I've reached all the stations equiped for coherent
reception - at least, with the available ERP.  Not much hope
of T/A unless much longer symbol periods are possible at LF.

I'm keen to dismantle the tx as soon as possible, transmitting
has been a lot of fun but I need to finish off some other things
before summer arrives.  Before taking down the antenna I'd
like to see how well the long wire works for ELF reception.
I don't expect it will work very well but it's worth a try
while it's there.  The wire wont last long anyway, the trees it
passes over will, before too long, saw through the insulation
and it will fail.

It might be possible to put up a more permanent antenna, 100m
long at 6m height might be feasible.  Less ERP but at least
it can be calculated and calibrated and it could stand a much
higher voltage.

Would be interesting to try VLF transmission but I'd have to
apply for a Notice of Variation.   The difficulty there is
that for the NoV I have to plan things in advance and estimate
ERP and so on, and have a particular purpose for it.   This is
probably one of the reasons there's been no UK VLF transmissions
for some time.  It's a lot of work and cost to gear up for VLF tx
only for the limited period of the NoV.   Nevertheless, I found
myself thinking about the costs and merits of kites and balloons.
There is, after all, the east-to-west T/A which hasn't been
done yet.

I started off in autumn making some improvements to the timing
program 'vttime' and the changes looked promising.  Putting it
to a stiff test by trying to coherently receive LF through
a sound card led to me needing an agile precision frequency
source so I wrote a new synthesiser program which worked well
enough to be worth giving it a name.  The test signal into
the rx wasn't strong enough so I needed a longer antenna to
produce enough near field and I made a multiplier to boost the
3rd harmonic for LF.   That led into transmitting which
has been a lot of fun and I've learned quite a few things.

But soon it is time to unravel these projects and close out
the next revision of vlfrx-tools.

--
Paul Nicholson
--

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