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From: "james moritz" <j.r.moritz@herts.ac.uk>
To: <rsgb_lf_group@blacksheep.org>
Date: Fri, 28 Jul 2006 11:54:31 +0100
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Subject: RE: LF: Tapped loading coil design spreadsheet
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Dear Bryan, LF Group,

>Surely if antenna impedance is lo and amplifier higher then the antenna
>needs to be
>tapped down from the top and the amplifier final  tapped "up" from =
there ?
>If moving the antenna tap detunes the the whole then  a 'bit of coil at =
the
>bottom' needs
>adding or removing ?

More or less - but the point is that, for any particular antenna, coil
diameter and winding pitch, there are only one or sometimes 2 =
combinations
of  TX and antenna tapping points that will work. Also, for quite a lot =
of
possible combinations of antenna, coil diameter and winding pitch, there =
is
NO combination of taps that will work.

>Mock it all up with infinitesimal power input , adust to matching /
>resonance.
>measure the inductances  and build a Big  Beefy copy.?

You could do this type of experiment, but it would be difficult to scale
everything to simultaneously maintain inductances, mutual inductance, Q =
and
stray capacitance at equivalent values to the full-size system, which =
would
be necessary to produce a valid result. Achieving this would be harder =
than
building the real thing! The spreadsheet calculations are an attempt to
theoretically predict the behaviour of the full-sized tuner, and so far =
seem
to give quite accurate results.

Cheers, Jim Moritz
73 de M0BMU