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Re: LF: ELF communications ?

To: [email protected]
Subject: Re: LF: ELF communications ?
From: DK7FC <[email protected]>
Date: Mon, 01 Dec 2014 21:32:42 +0100
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Hi Dimitris,

Well, i have had 2 of these HV transformers. The first one got an internal fault during the experiments. A few weeks later i took the second one and wanted to repeat the experiment but i found that it was shorted from the beginning on. BUT, last friday we bought another HV transformer of a similar type for an application at work. This one even generates 18 kV and 40 mA! I will repeat the experiment then.
Regarding VLF, i do not think that one can get 100% or even 30% of the
rated voltage at frequencies above a few 100 Hz. The stray-C of the
secondary turns is much to high. Also the core of the transformer will
not work at a few kHz. For a 10 kV transformer i would guess and expect
5 kV at 500 Hz when using a high resistive load.
But just give it a try.

Aaah, i understand, it is summer in VK and you want to go out in the field, trying a ground dipole, 2x 10 km? :-)
73, Stefan/DK7FC

Am 01.12.2014 21:19, schrieb Dimitrios Tsifakis:
Hi Stefan,

This afternoon i'm attempting to transmit on my INV-L on 136.172 Hz (not
kHz!). Just preparing my H bridge VLF PA and i intend to use an old 10 kV
transformer which i got from an old furnance (to inflame the oil stream),
see https://dl.dropboxusercontent.com/u/19882028/VLF/10kV%20Trafo.jpg
Have you done any more tests with this? I am curious to see the
results. Would this idea work on VLF as well? I have come across some
power toroid transformers that have a reasonablywide useful bandwidth
that extends in the VLF part of the spectrum and perhaps such a
transformer connected to a really nice amateur LF/MF antenna could be
a very quick way of getting a small signal on VLF?

73, DImitris VK1SV





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