Message-ID: <004601c10cb2$a9e5b480$828801d4@g4jnt>
From: "Andrew Talbot" <G4JNT@thersgb.net>
To: rsgb_lf_group@blacksheep.org
Subject: LF: Re: re 9kHz NOVs
Date: Sat, 14 Jul 2001 23:16:41 +0100
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Alan -
We need to be realistic about the types of inductor feasible for
transmitters at this frequency.  With an antenna capacitance of 270pF and
inductor of 1.2H or so at 9kHz, the number of turns needed to prevent core
saturation will be astronomical for realistic power levels - gaps will only
help to get the inductance back down for the number of turns needed.   It is
volt . turns that saturate cores, gaps have nothing to do with preventing
saturation of inductors at AC,  they just allow the inductance to be
defined.   With a reactance in the region of 80k ohms, only a fraction of an
Amp will give many kV on the antenna.  Apparantly,  Rugby at one time in its
history running a few 10s of kW was reckoned to have 500000 Volts on its
antenna.

I sent my NoV application in via RSGB Licensing Advisory Committee.  ie Sent
it via Julian Gannaway,  G3YGF, who is persuing it with the RA.   He lives
just 6km away from me and is interested in LF himself - in fact was one end
of my very early record setting distances on 73kHz before everyone started
coming on with their big antennas.

I've started long term monitoring of the Earth's mag field now.   The old
286 laptop is in the shed recording the magnetometer output every 5 minutes.

Andy  'JNT


-----Original Message-----
From: Alan Melia <Alan.Melia@btinternet.com>
To: LF-Group <rsgb_lf_group@blacksheep.org>
Date: 14 July 2001 22:20
Subject: LF: re 9kHz NOVs


>Hi Andy, if you think it might help the cause.....where did you apply to??
>and I will prepare an application as well. You wont be able to do real
>experimentation unless there are a spread of operational stations for
>reports etc.
>
>As to 1.4H coils try measuring the inductance of some old audio
>transformers, and mod transformers, maybe the odd C-core power transformer.
>I think you might find them in the right kind of range, though you may need
>an air gap (??) I have a torroidal line transormer (100v line..... I think
>its called) from an old slave audio amp that looks about right, and is
>certainly good to about 40kHz. Insulation could be another problem though
!!
>
>Cheers de Alan G3NYK
>Alan.Melia@btinternet.com
>
>
>
>