Also been considering the ground loop option but for 136kHz- I can't
recall any reference to this being tried anywhere by the amateur
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
mountain core
Barr, R.; Ireland, W.; Smith, M. J.
IEE Proceedings, Part H - Microwaves, Antennas and Propagation (ISSN
0950-107X), vol. 140, no. 2, p. 129-134.
The establishment of an LF/VLF/ELF transmitting facility at the Homer
tunnel near Milford South in the South Island of New Zealand is
described. The antenna consisted of a 3.3 km-long PVC-covered aluminum
conductor passing through the tunnel and over the mountain above,
forming a large vertical loop antenna. Measurements of the electric
field radiated from the transmitter, recorded at both Lauder and
Palmerston, 133 and 225 km from the transmitter site, respectively,
are presented. The antenna radiation pattern derived from observations
made onboard an Orion aircraft circling the antenna at a distance of
200 km is also presented. Theoretical models are derived which enable
fits to the radiated field data to be made over a wide frequency range
(0.5-40 kHz). With 1 kW of input power the antenna produced peak
radiated fields at frequencies near 10 kHz equivalent to those of a
vertical monopole source radiating 150 mW.
Finding a convenient hill and tunnel might be a challenge though!
73
Dave, ZL3FJ
----- Original Message -----
From: "Andy Talbot" <[email protected]>
To: <[email protected]>
Sent: Tuesday, March 09, 2010 7:42 AM
Subject: LF: VLF
...wishing I'd persued the NoV application a few years ago instead of
just
letting it slide into oblivion...
Has anyone yet tried a ground loop at 9kHz? That was going to be my
first
(and probably only) antenna type, running a length of wire as far away
from
the house as I could get-away with and connecting it to a ground
stake, then
feeding this against the existing local earth. I never got round to
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
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
would
have made a useful route to hide a wire in. Might have been
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 Büscher <[email protected]>
Hi Stefan,
A VLF grabber would be very fine! If you can arrange that, it would
perhaps
be a motivation for the dreamers ;-)
Well there are two now (Markus' and Paul's) .. I will try to add a
third
but need to get away from the local QRM. The plan is to use an UHF
FM link
to the remote, battery-powered site but there are some issues to be
solved -
one of them is the lack of dynamic range of the FM
transmitter/receiver, so
I may have to add some analog bandpass filtering before the FM
modulator
(which would render it useless for broadband VLF signals, especially
natural
radio signals..).
Will keep you informed, when/where another VLF 'live spectrogram'
goes
online.
Cheers,
Wolf .
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