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Message-ID: <wQTcZAA6H5d4EwHf@dennison.demon.co.uk>
Date: Sat, 8 Jan 2000 19:37:30 +0000
To: rsgb_lf_group@blacksheep.org
From: "Mike Dennison" <mike@dennison.demon.co.uk>
Subject: Re: LF: LF antenna
In-reply-to: <3.0.1.16.20000104153138.2f4797da@mail.cc.kuleuven.ac.be>
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ON7YD wrote:
>A bit desperate I started my final attempt, again inspired by Mike,
G3XDV,
>who reported an improvement of his antenna by adding some inductance at
the
>top of the vertical section of his antenna. [big cut] DCF39 seemed
about a S-point stronger, but that could be
>just QSB. Also G3AQC who was CQ-ing sounded stronger, but the ear can
be
>very subjective. I called Laurie, being curious about my report. To my
>pleasure I got a 1 S-point better report than I got so far from him, so
it
>was not just my imagination that despite the lower antennecurrent
signals
>were stronger.
>The same evening I managed to work Finbar, EI0CF, (got 439 / 539) for
the
>first time after having called him over and over for the last year.
>The next days reports from several stations (G4GVC, G3YXM, DK8KW)
showed an
>increase of 1 S-point.


Very interested in this report from Rik. At the time I announced my
success, Rik spent some time running through the maths with me to show
that theoretically there should be no improvement - and I could not
argue with that. I recall replying that if practice and theory did not
agree, believe the practice. Recently, Dick, PA0SE, also argued
mathematically and by modelling that there was no improvement to be had.

Later, after many e-mails and discussions with others, I came to wonder
whether my experience was unique, and was probably due to the vertical
part of the antenna being very close to the house (therefore anything
that increased the current high up - above the house - gave me a better
signal that it would for anyone else). This, of course, could still be
true as Rik has considerable screening by trees.

I shall be shorting out the top coil later this month so I can use the
antenna in the CW WW 160 contest, and will carry out some before and
after tests at that time.

I believe that optimum results should occur when the antenna is made
self-resonant, but I suspect it will be affected badly by changes in the
environment (trees in summer/winter, rain, ice, etc).

It's probably not worth reopening the debate which has already been well
aired, unless someone can make the maths fit the experimental results.
-- 
Mike, G3XDV
IO91VT
http://www.dennison.demon.co.uk/activity.htm