W7ALW said:
>Since I'm planing to shunt feed a 70' tower before this coming fall, I'd
be
very interested in discovering good information on the cage-vertical.<
I shunt my feed my 62 foot tower (top loaded with a 4 ele Steppir now) on 80
and 160 with just such a 'wide conductor'. Three wires in the same plane,
about 8 inches between them. For spreaders, I use copper water pipe - you
can run the wire through holes in the pipe, and put on a binding wire.
Worth soldering the whole lot up though. Although I have used ordinary tin
lead solder, it eventually degrades, I find, and so now I use silver solder
to BS1845 grade AG2, also known as Easyflow No2 in the Johnson Mathey range.
That's a hard solder of 42% silver, 17% copper,16% zinc and 19% cadmium,
with a solidus temperature of 610C and a liquidus temperature of 620C. You
need special flux for it, but that's fairly easy to get from the same
source as the solder itself, and of course, a propane or butane gas torch -
it need to get literally red hot. The flux is a powder which you mix with
water to a paste, and apply liberally. Of course, the metal needs to be well
cleaned first. I haven't noticed any corrosion after it's been outside,
although it's worth dropping some cold water on the joint once it's
solidified to remove any remaining flux. Note that when silver soldering,
you MUST not have any tin lead solder in contact with it.
I find it works very well. I have no radials at all - just 4 off 4 foot
earth rods. The ground is thick wet blue clay from about 6 inches down. I
tried both ground mounted and elevated radials, and found adding them made
no measurable difference to the feed point impedance, and in neither case
could I measure any current in them.
However, I've worked such niceties as VK0 Heard Island on 160 with
it...........a PY in the middle of summer........3B9C of course.
All this was with the top loading consisting of a 205BA at 62 feet, and an
interleaced 4 ele for 10 and 4 ele for 15 at 68 feet. The Steppir offers
less loading, and the resonance point is now within 80metres. This means
that the impedance at the end of the feed line varies wildly enough that I
need two variables in the L network tuner rather than just one, so a current
project is rebuilding the remote tuner to handle this - in between foreign
business trips, which are causing a major delay in the project.
73
Peter G3RZP
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Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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