Message-ID: <1999112214225868199@zetnet.co.uk>
Date: Mon, 22 Nov 1999 14:22:58 GMT
To: rsgb_lf_group@blacksheep.org
From: "Peter Dodd" <g3ldo@zetnet.co.uk>
Subject: LF: Re LF General
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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

<g3ldo@zetnet.co.uk>