========================================
Message date : Nov 17 2004, 09:20 AM
From : "OSBORN, Chris"
To : "LF Group (E-mail)"
Copy to :
Subject : LF: Loading Coils
Hello LF Group
Many thanks for all comments and advice - most interesting.
I drilled out the wooden dowels on the loading coil and replaced
them with lengths of 15 mm plastic water pipe.
I was unable to obtain plastic rod at short notice and my XYL
wouldn't let me have her knitting needles !
The pipe was not really rigid enough and bent slightly but was
sufficient to prove the experiment.
With this new arrangement I obtained my personal best Q of about
250..
Placing the new coil in the aerial circuit made a slight improvement
to the aerial current - from about 1.2 A to 1.5 A
I would have thought that as most of the losses were in the coil a
bigger current improvement w
ould have been achieved.
I share my office with some young electronics engineers and was
surprised that they know very little about RF inductors or Q factor.
It must be a dying art !
My next improvement will be to raise the 'droopy' end of my aerial,
presently at a height of about 5 metres
Unfortunately two neighbours' telephone wires pass over my garden
where the mast was to be situated.
Any suggestions - should I go over the wires or keep well clear of
them and cut a length off the aerial ?
Presumably I can't get the phone company to move their wires !!
73 Chris G3XIZ
Hi Chris,
Major losses are ground losses ! This is very difficult to overcome, buried radials do not seem to help presumably because the lengths that most of us can manage are too short. I have found that by far the best way if lowering losses is to put more wire in the air. One meter of wire in the air is worth 100m in the ground ! This extra wire does not have to be in a straight line but it must not be too close to existing wires.So try a zig zag or radial top hat. Do try to raise the low end also since this works against the height of the vertical section and lowers the radiation resistance.
Best of luck Laurie.
