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From: "james moritz" <j.r.moritz@herts.ac.uk>
To: <rsgb_lf_group@blacksheep.org>
Date: Mon, 31 Jul 2006 13:59:14 +0100
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Subject: LF: RE: Antenna or transmitter tuning
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Dear J, LF Group,

It is unlikely the distorted waveform is due to saturation of the
transformer core. To have any noticeable effect on the waveform, it =
would
have to be driven quite deeply into saturation, and at 137kHz, this =
would
cause it to get smoking hot very quickly due to the core losses. In
practice, it is hard to do this with any reasonably sensible windings. =
In
any case, the low pass filter should then largely filter out the =
distortion.

I found that corona discharge makes the oscilloscope display "flicker" =
with
rapid changes of amplitude, although the waveforms do not look distorted =
as
such. I would be surprised if you are getting corona with your antenna - =
the
large length of wire means high capacitance, and so voltage no more than =
a
few kV.

It would certainly be a good idea to check the output with a 50R load =
using
the oscilloscope. To make sensible comments, it would help to know:
What kind of amplifier circuit is in use?
What kind of low-pass filter is in use?
At what point in the system is the "scope match" connected?
What do the awful waveforms look like? (a picture or sketch would help a =
lot
here...)

Cheers, Jim Moritz
73 de M0BMU