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 [email protected]
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
<[email protected]>>
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