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LF: Re LF General

To: [email protected]
Subject: LF: Re LF General
From: "Peter Dodd" <[email protected]>
Date: Mon, 22 Nov 1999 14:22:58 GMT
Reply-to: [email protected]
Sender: <[email protected]>


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

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