From: Rik Strobbe <rik.strobbe@fys.kuleuven.be>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Thread-Topic: A transductor instead of a traditional variometer on VLF/LF/MF?
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Date: Sat, 14 May 2016 19:08:55 +0000
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Subject: LF: Re: A transductor instead of a traditional variometer on VLF/LF/MF?
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Hi Stefan,

that could work. 
Long time ago I did read an article on magnetic amplifiers from a K7... ham (if I remember well).

73, Rik  ON7YD - OR7T
________________________________________
Van: owner-rsgb_lf_group@blacksheep.org <owner-rsgb_lf_group@blacksheep.org> namens DK7FC <selberdenken@posteo.de>
Verzonden: zaterdag 14 mei 2016 14:01
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: LF: A transductor instead of a traditional variometer on VLF/LF/MF?

Hi all,

During thinking about a solution for a automatic variometer for my VLF
coil i got the idea of using a transductor instead. Will this work?
See:
https://de.wikipedia.org/wiki/Transduktor_%28Elektrotechnik%29
https://en.wikipedia.org/wiki/Magnetic_amplifier

On LF/MF and VLF many of us are using typical variometers for manual or
automatic resonance correction of the transmit system.
Due to the multi-layer VLF TX coil with a forced air flow in the center
it is not easy (or not possible) to put an additional rotatable coil in
the center to adjust the resonance frequency within a small range. So i
need another solution.
One solution could be to accept the non-resonance and run a higher
voltage on the output transformer to keep the antenna current constant.
But this will cause losses on the linear working PA and works only in a
very limited range, due to the Q of the system.
So it would be better to have a chance to steer the resonance anyway!
But how?
Now, what about a transductor?
A ferrite core inside the main field of the coil. It must have a winding
and a variable DC current from an external power supply. The DC current
can saturate the core and change its effective 皴 for the external AC
magnetic field.

If this works, then it is a non-mechanical solution! No motor, no axis,
no end switches, no mechanical self oscillation, no broken RF litz wire
on the rotating elements, fast changing of the resonance frequency.

Has someone tried that on LF before?

73, Stefan

PS: I will start to try that on VLF, IMMEDIATELY! :-)