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From: =?UTF-8?Q?Wolfgang_B=c3=bcscher?= <dl4yhf@freenet.de>
Message-ID: <5720F2DB.3030704@freenet.de>
Date: Wed, 27 Apr 2016 19:11:55 +0200
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Subject: Re: VLF: A single turn RX loop for VLF
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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).
>