Message-ID: <001401c08f54$e9264c80$9c1686d4@ericadodd>
From: "g3ldo" <g3ldo@ukonline.co.uk>
To: rsgb_lf_group@blacksheep.org
Subject: Fw: LF: GB2CPM
Date: Mon, 5 Feb 2001 09:19:53 -0000
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Sender: <majordom@post.thorcom.com>

I sent this report on Saturday but it only found its way to Steve; so I am
trying to resend it. The problems with this e-mail system seem to be
confined to reception so I am reading the reflector via g3ldo@zetnet.co.uk


> I planned to work at GB2CPM on Friday but it rained all day so it was
called
> off
>
> > > If all goes well I will operate on CW late
> > > morning until early afterenoon.
>
> Steve said
> > I hope that the earthing and antenna work is successful.
> >
> > I will try to 'phone G8IK; G6RO; G8RW; and G6NB later this
> > morning (Friday) to advise them of your plans.  They are often
> > QRV during weekdays.
>
> I thank you for your promotional efforts Steve and I'm sorry I couldn't
make
> it. Furthermore my service provider e-mail was off so I couldn't tell
> anyone.
>
> However, I did get there today (Saturday). The primary objective was to
work
> on the antenna system. I forgot my digital voltmeter so I couldn't use the
> 3-M impedance meter. However I think I made progress.
> The recap, the antenna at GB2CPM is an inverted L with a 150m top and a
35m
> vertical, strung across a valley created by years of chalk extraction. It
> should be a good antenna but it is very difficult to find an RF ground and
I
> use two radials, each around 200m long laid on top of the earth surface.
> This system works but the feedpoint is at a fairly high RF voltage. It
only
> works because the antenna, loading coil and tuner are isolated from ground
> and the rig with the ferrite transformer.  If the base of the loading coil
> and the radials are earthed the antenna will not work.
> I did some approximate impedance measurements on the original antenna
layout
> using two multiple tapped ferrite transformers.  From these 'measurements'
I
> feel that antenna can be thought of as a short dipole with the feedpoint
> offset from the electrical centre - hence the high RF potential.
>
> I then earthed (the best I could) the base of the loading coil. The
resonant
> point changed and became very broad - although this time it was safer but
> didn't work as well. I feel that this move just inserted a large
resistance
> into the feedpoint somehow.
> I have tried resonating the radials in the past but found I had too many
> variables to control at the same time (radial resonance, antenna resonance
> and impedance matching).
> I have two options, one is go for just one radial and extend it to around
> 500m. The problem is that the area is forested with a lot of undergrowth.
> The second option is to use a large metal building, located about 80 or
90m
> away from the 'shack' as a ground. The downside of that is that the earth
> wire has to be laid across a road.
>
> While the antenna was in 'safe' mode I heard G4HYU working GW4ALG. Later I
> worked John, G4CNN, who said I was not as strong as the last time I was
on.
> I heard PA0SE and gave him a call and got a QRZ - normally I can work Dick
> without any problem from that location.
> G3XDV was S9+, his signal ringing out all over the Amberley Museum site,
> working DL3FDO.
>
> I did suggest this site as a combined site for a transatlantic effort.
> However, the problems with the antenna, plus the mud and the additional
> industrial junk that has been dumped around the operating spot make it
less
> than ideal. Nevertheless, watch this space.
>
Regards,
Peter, G3LDO

<g3ldo@ukonline.co.uk>>