Dear Tony, LF Group,
The most important parameter of an LF vertical antenna is its height, more
specifically the "effective height", which, for antennas that are a small
fraction of a wavelength in overall length, is roughly speaking the average
height of the conductors making up the antenna. Increasing the length has
secondary benefits, but height has by far the strongest effect on overall
efficiency. The resistance of the wire will contribute to overall losses,
but at LF this is relatively low due to the reduced "skin effect" compared
to higher frequencies. So even fairly thin wire will probably add no more
than a few ohms to the overall loss resistance, and this will be reduced if
you go for the parallel 2-wire configuration.
So the main thing is to go for robust, reasonably light weight wire that can
be put under enough tension to minimise sagging and so reduction of the
height. I have used the tri-rated switchgear cable favoured by G7NKS for 10
years now without problems, but I guess any stranded, plastic sheathed cable
would be about the same. One could split up mains cable to get this quite
cheaply if specialist suppliers are not convenient. The solid-cored "twin
and earth" mains cable is probably the cheapest and easiest to strip the
outer sheathing off, and the inner cores are very robust although obviously
less flexible. Probably the smallest 1mm^2 gauge would be fine.
I have tried using copper coated MIG welder wire for antennas, but as G3YMC
says, the coating is too thin and quickly rusts through. There is such a
thing as "copperweld" wire with a thicker copper cladding, but this is quite
a specialised thing. Electric fence wire looks tempting, but usually has
stainless steel strands with a high RF resistance. A lot of the el Cheapo TV
coax around has a copper-plated steel centre conductor with an outer
consisting of a few strands of braid with an aluminium foil, and in my
experience is well worth avoiding for any application!
Cheers, Jim Moritz
73 de M0BMU
----- Original Message -----
From: "Tony Baldwin" <[email protected]>
To: <[email protected]>
Sent: Friday, June 25, 2010 10:35 AM
Subject: Re: LF: Antenna wire
Would welding wire do, the CO2 welding wire about 1mm copper coated steel
wire ?
That I already have a roll of and it's available in Lidl this week.
Tony, EI8JK.
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