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Date: Mon, 14 Mar 2016 16:59:09 -0400
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Subject: RE: LF: EbNaut from Todmorden
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"... thinking about the costs and merits of kites and balloons."

Kite/balloon = helikite, which provides interesting low-cost options for
stable one-man deployment and operation, especially if a pickup truck is
available. At some interesting VLF ERP levels, with a pickup truck
available, it's not necessary to have a winch or commercial ground anchors,
such that cost converges to helikite and helium, i.e. low cost. 

At lower ERP levels (antenna heights less than 200 meters), a pickup truck
would not be necessary, and if some wind is presumed, a particularly low
cost helikite could be used.

Advantages of a helikite approach include vertical operation in still air,
and good elevation angles in high winds. 

73,

Jim AA5BW
 

-----Original Message-----
From: owner-rsgb_lf_group@blacksheep.org
[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Paul Nicholson
Sent: Monday, March 14, 2016 3:34 PM
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: EbNaut from Todmorden


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
--