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From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <68BE37BD69E54DEE89CEBA8E30E9B94E@PcMinto> <4E47FFE9.10100@iup.uni-heidelberg.de> <3ED8E5422F1F45DBB8186E9D9870AD63@PcMinto> <4E480E02.9020706@iup.uni-heidelberg.de> <938BF599006244949F6CDDB5BA91F347@PcMinto> <4E482FBD.7030402@freenet.de> <4E484183.9090805@iup.uni-heidelberg.de> <op.vz74xbyxyzqh0k@pc-roelof> <4E48556B.7030906@iup.uni-heidelberg.de>
Date: Mon, 15 Aug 2011 00:58:31 +0100
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Subject: Re: LF: Ferrite RX antennas
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I am afraid the tone of the article makes me a skeptic :-)) but if his first
former was 12mm diam and his bigger pictured one a120mm diameter the factor
A =100 in the conventional loop equation....so 20dB ...???????  extra
ferrite cross sectional area does help too, plus bigger former less turns
for the inductance less copper loss, higher Q (also increases the output).
Better but no magic!

For some experimental measurements see a Electonics World article  on Loops
by a couple of Itallian amatuers (app 2004 or 2005). Having said that there
may be some mileage in not winding the coil direct on the ferrite. Ferrite
is a lossy "semi-conductor" .It might be interesting to screen the core
electrostatically from the coil (it need a logitudinal slot to avoid a
shorted turn effect.) ....but this has probably been tried by many before.
Accurate comparative measurements on a reliable signal like DCF39 would be
much more interesting.

Alan G3NYK


----- Original Message ----- 
From: "Stefan Schäfer" <Stefan.Schaefer@iup.uni-heidelberg.de>
To: <rsgb_lf_group@blacksheep.org>
Sent: Monday, August 15, 2011 12:08 AM
Subject: Re: LF: Ferrite RX antennas


> Interesting!
>
> Can anyone of the experts comment on this concept?
>
> After scrolling down through pages of text i just found a few photos.
> The mechanical concept is clear.
> But the author appears almost esoteric to me, like a guru of that
> antenna,  "_*The best compact AM antenna in the world - ever!"
>
> *_So it is said that 20 ferrite rods in that arrangement perform 20 dB
> better than a single rod. OK, but how well performs such a signgle rod?
> 20 dB is maybe not enough, compared to a well designed single turn loop,
> which i have now.  My goal is always LF/137, not MF BCD stations or so.
> The advantage of the ferrite solution, if sensitivity is sufficient to
> be well above the noise on a quiet day, would be to be completely free
> in all /p sesions (without a car).
>
> Would it be possible to reasonable simulate that antenna (not an
> accurate model but rather an estimation)?
>
> 73, Stefan/DK7FC
>
>
> _*
> *_Am 15.08.2011 00:04, schrieb Roelof Bakker:
> > Hello all,
> >
> > If you have time to read it all, this might be interesting:
> >
> > http://www.gmweb2.net/The%20FS%20Loop.htm
> >
> > or Google for Ferrite Sleeve Loop.
> >
> > 73,
> > Roelof, pa0rdt
>