Message-ID: <005e01c2a79b$c35fcc40$1e1686d4@erica>
From: "g3ldo" <g3ldo@ukonline.co.uk>
To: rsgb_lf_group@blacksheep.org
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Date: Thu, 19 Dec 2002 20:17:28 -0000
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Subject: LF: Re: antennas
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Mike G3XDV said
>
> No. Sorry if I was unclear. I have three top wires, 18m long, running
> parallel and spaced 0.5m apart. The wires have always been joined at the
far
> end, and this helps reduce the corona losses. I also had them joined at
the
> feed end, next to the elevated loading coil at the top of the vertical
> section. What I did was to disconnect the join at the feed end, so that
the
> coil fed just the centre wire. The current then went along this centre
wire
> to the join at the far end, and returned along the two outer wires. This
is
> what increased the resonant frequency when I would have expected the extra
L
> in the top wires to decrease the frequency. I have concluded that the
> shorting wire close to the coil was probably having a capacitive effect on
> the coil and reducing the overall frequency. Whether the top wires are
> electrically in parallel or series seems to make no difference at all.

I checked with your original e-mail description and found that I had got it
all wrong. Still nothing lost, I had wanted to try and see if increasing the
spacing of the two wire top load from an average of 2m to 4m would change
anything. In the event it did not.  I will be transmitting tonight as part
of my antenna current puzzle measurements on 72.4003. At this time the
ground has dried out and the antenna current at 1600 was 4.9 amps, which
fell to 4.1 amps by 1930

I am interested in Dexter's loop. My 4m square loop (described in the web
page below) uses a single turn coupling turn and coax back to the receiver.
It works reasonably well having been used in a 'reverse' T/A 136/80m
crossband in Feb 2001 with VE1ZZ but he had a very big signal. What preamp
circuit did you use Dex?

As regards using big antennas on LF, many operators using a temporary big
mast had problems on receive. Big antennas seem OK provided a variable
attenuator and a good passive preselecter are used.

Regards,
Peter, G3LDO

e-mail <g3ldo@ukonline.co.uk>

Web <http://web.ukonline.co.uk/g3ldo>