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Re: VLF: A single turn RX loop for VLF

To: [email protected]
Subject: Re: VLF: A single turn RX loop for VLF
From: Wolfgang Büscher <[email protected]>
Date: Wed, 27 Apr 2016 19:11:55 +0200
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Hello all,

I can confirm such a single-turn loop with a big ferrite transformer works well - even with a very simple amplifier.
Construction details and a few spectrograms at :
http://www.qsl.net/dl4yhf/vlf_rdf/vlf_single_turn_loop.htm

(this 'ferrite cylinder' can frequently be seen at hamfests, but none of the dealers could tell who actually made them, and what their original purpose was..)
Cheers,
   Wolf .

Am 27.04.2016 um 18:31 schrieb DK7FC:
Hi VLF,

Today i've installed a second loop into the tree. It is a simple copper tube having 10 mm diameter and about 4m length.
https://dl.dropboxusercontent.com/u/19882028/VLF/20160427_084708.jpg
The loop is not resonated. The ends are just hold together with a screw.
https://dl.dropboxusercontent.com/u/19882028/VLF/20160427_092012.jpg
It is a very stable / robust construction which needs no further elements to hold it into the tree. The screw is protected against rain with some bonding tape. Before the mounting, a ferrite transformer with Al ~ 6000 nH was put on the tube.
First i tried 20 secondary turns.
https://dl.dropboxusercontent.com/u/19882028/VLF/20160427_092420.jpg
Later i choose 40 turns and finally 80 turns.
The results between the N-S loop and the E-W loop are still visible at http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html
DHO38 is much weaker, the Alphas are much stronger, HWU is stronger.

All in all it appears that this loop performs better then my 80 turn hula hup circle loop (0.8m diameter). And by using the transformer it can be adapted optimally to the preamp input impedance. It even works down to 100 Hz, with limited performance of course.
I'm now looking forward to receive something from the East or West. Is
there someone out there ready to radiate a signal?
Also, a VLF RDF grabber would be fine, maybe even by using idenetical
antennas (to be built).
73, Stefan

PS:
BEWARE: This is not new! Someone has done it before, maybe even in the 1920s. VLF receptions on the Dreamers Band were done with such a loop for example by F5WK (http://f5wk.blogspot.de/2010/09/antenne-loop-vlf.html).

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