First of all I would like to take my hat off to The Two Daves and a
Graham who did such a wonderful job with the GD expedition. Only if
you have ever tried to operate from a different site with an antenna
with unfamiliar (and variable!) characteristics can you appreciate the problem.
In the early days of experimenting with 73kHz I was aware of a
background 'galloping horses' sound, which G3JKV identified as the
sidebands from Loran on 100kHz. On 73kHz this background QRM was not
intrusive and was a good indication that the receiver system was on
the 'nose'. Prior to the 73kHz tests with GD0MRF/P I made a number of
signal measurements. Loran was nowhere to be seen or heard. My
conclusion is that the noise floor is about 10dB higher than it used
to be, even at 170km distance from the 'growler' at Rugby. There is
no sign of discreet sidebands like on Loran, just higher noise.
After the 73kHz QSO with GD0MRF/P on Sunday I packed up all the radio
gear and headed for Amberley museum. My vintage Shogun is ideal as
the shack, first to get to the location in chalk mud at the bottom of
the chasm and as a comfortable operating place. I have access to
power via a 150m long extension (hyper) lead.
The antenna had not been tested since it was re-erected and
relocated. Disaster! no antenna current. Checked the counterpoise,
lifting it out of the mud and fixing it on boulders. Antenna current
now about 30mA. Called G4GVC at 1120 and got 589. While the QSO
progressed the antenna current slowly increased and with a bit of
retuning the antenna current was 50 or 60mA (and my report was
modified to S9) by the end of the QSO. I added an extra counterpoise
wire and increased the antenna current to 1.4A. Worked GW4ALG, PA0SE
and GD3YXM/P (from the house using the non-kite antenna). Heard G3KEV
calling CQ but he didn't appear to hear me.
At 1320 worked EI0CF, 559, PA0BWL,559, G3XDV 599, G6RO 569, G3YMC
579, GD0MRF/P 599.
The interesting thing about this antenna system is that it is
'floating' above earth. If I attempt to ground it to the vehicle or
mains earth the current falls to zero. My feeling is that the
matching system I am using does not have the impedance range to match
an antenna system that is very much different to that used at the
home QTH. The floating antenna system works quite well but the
loading coil appears not to be in the centre of the system. When I
deployed the second short radial I touched it on the 'earth' side of
the coil while the transmitter was on and got an alarming 100mm arc
and an increase in antenna current. Looks like a good QTH for tuned radials.
--
Regards, Peter, G3LDO
<[email protected]>
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