Message-ID: <5C39EB1D.5080104@posteo.de>
Date: Sat, 12 Jan 2019 14:26:53 +0100
From: DK7FC <selberdenken@posteo.de>
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Subject: Re: LF: a lot of ferrite
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Hi Dimitris,

Interesting. BTW, it's a long time ago that we read from you. You have 
been VK1SV some years ago, right?
I remember your websites and experiments with some long wires laying on 
the ground. I wish to have such a wide area for experimenting like you 
have :-) Recently i searched for one of your websies where you described 
an experiment using 2x 100m of wire, if i remember correctly. But the 
page was not found. Can you tell me the link, if it is still existing?

Well, i see no advantage in a RX antenna when using such rods. Maybe you 
can build a RX loop antenna a bit more compact but then it will be very 
heavy and the air gap (changing with temperature and mechanical forces) 
may affect the phasy stability.
For a TX antenna i see no advantage either. An AL value of 1 uH can be 
reached with most high mu ferrite toroids...

However, maybe you could build a H field RX antenna for frequencies 
below 1 kHz, something like http://www.vlf.it/romero3/ics101.html or 
http://www.vlf.it/matteobruna/ULF_Induction-Coil.htm

73, Stefan


Am 12.01.2019 04:48, schrieb Dimitrios Tsifakis:
> Hi LF group,
>
> I have managed to acquire a few very large ferrite rods (36 cm x 10 cm
> x 2 cm). The material is unknown but I managed to form a square
> 'toroid' with four of them (they are heavy so gravity was enough to
> keep everything in place for a measurement) and I measured about 15 uH
> for 4 turns at 0.1 MHz, which if I have done the calculations
> correctly implies a relative permeability of about 1000.
>
> The R of the impedance of the square loop was low (<0.2 ohm) at 0.1
> MHz and it increased fast with frequency (170 ohm at 5 MHz!).
>
> The question is, what LF/VLF experiment would you do if you had half a
> dozen of these rods?
>
> 73, Dimitris VK2COW
>
>