Message-ID: <3aba01cabef5$25589df0$7900a8c0@athlon1200>
From: "Dave Brown" <tractorb@ihug.co.nz>
To: <rsgb_lf_group@blacksheep.org>
References: <fc7eccec1003081042w42631ff5w61d4bf06f8c49479@mail.gmail.com>
Date: Tue, 9 Mar 2010 08:25:39 +1300
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Subject: LF: Re: VLF
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Also been considering the ground loop option but for 136kHz- I can't=
=20
recall any reference to this being tried anywhere by the amateur=20
fraternity. If it has been tried, what were the results?

 Another option for VLF might be along the lines of this--
ELF, VLF and LF radiation from a very large loop antenna with a=20
mountain core
Barr, R.; Ireland, W.; Smith, M. J.
IEE Proceedings, Part H - Microwaves, Antennas and Propagation (ISSN=
=20
0950-107X), vol. 140, no. 2, p. 129-134.
The establishment of an LF/VLF/ELF transmitting facility at the Homer=
=20
tunnel near Milford South in the South Island of New Zealand is=20
described. The antenna consisted of a 3.3 km-long PVC-covered aluminum=
=20
conductor passing through the tunnel and over the mountain above,=20
forming a large vertical loop antenna. Measurements of the electric=20
field radiated from the transmitter, recorded at both Lauder and=20
Palmerston, 133 and 225 km from the transmitter site, respectively,=20
are presented. The antenna radiation pattern derived from observations=
=20
made onboard an Orion aircraft circling the antenna at a distance of=
=20
200 km is also presented. Theoretical models are derived which enable=
=20
fits to the radiated field data to be made over a wide frequency range=
=20
(0.5-40 kHz). With 1 kW of input power the antenna produced peak=20
radiated fields at frequencies near 10 kHz equivalent to those of a=20
vertical monopole source radiating 150 mW.

Finding a convenient hill and tunnel might be a challenge though!

 73
 Dave, ZL3FJ


----- Original Message -----=20
From: "Andy Talbot" <andy.g4jnt@googlemail.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, March 09, 2010 7:42 AM
Subject: LF: VLF


...wishing I'd persued the NoV application a few years ago instead of=
=20
just
letting it slide into oblivion...

Has anyone yet tried a ground loop at 9kHz?   That was going to be my=
=20
first
(and probably only) antenna type, running a length of wire as far away=
=20
from
the house as I could get-away with and connecting it to a ground=20
stake, then
feeding this against the existing local earth.   I never got round to=
=20
making
measurements to see what sort of ground resistance might be
expected, but that would have been a lot easier than winding 1.4H air=
=20
wound
chokes.

My house backs onto a main road, and there is a drainage ditch running
behide trees and foliage running for about 70m in one direction that=
=20
would
have made a useful route to hide a wire in.  Might have been=20
interesting
hammering in a ground stake next to the footpath at the corner of the
next road though !

Andy
www.g4jnt.com


2010/3/8 Wolfgang B=FCscher <dl4yhf@freenet.de>

> Hi Stefan,
>
>
> A VLF grabber would be very fine! If you can arrange that, it would=
=20
> perhaps
>> be a motivation for the dreamers ;-)
>>
>>
> Well there are two now (Markus' and Paul's) .. I will try to add a=
=20
> third
> but need to get away from the local QRM. The plan is to use an UHF=
=20
> FM link
> to the remote, battery-powered site but there are some issues to be=
=20
> solved -
> one of them is the lack of dynamic range of the FM=20
> transmitter/receiver, so
> I may have to add some analog bandpass filtering before the FM=20
> modulator
> (which would render it useless for broadband VLF signals, especially=
=20
> natural
> radio signals..).
>
> Will keep you informed, when/where another VLF 'live spectrogram'=20
> goes
> online.
>
> Cheers,
>  Wolf .
>
>
>



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