Hi Randy: Will the tower have a yagi on top? How tall is it? You do not
have to insulate the tower base. You need something to connect the coax
shield to at the base of the tower. If you can drive a few ground rods
at the base you can make it work but efficiency will not be very high.
If you can connect the fence and metal roof to the ground system it will
help the efficiency. Wires beside the sidewalk or along the borders
connected to the ground rods/coax shield will help. There is a scheme of
making a large "needle" out of a piece of pointed rod and sliding it
along the ground beneath the grass to carry radial wires out from the
tower base that can be used. Even if the wires are not 1/4 wave long,
they will really improve the efficiency. You will probably need to
connect a wire to the tower top or somewhat below it, spaced from the
tower 1-3 feet and drop it down to the base. A gamma or ,more likely a
omega match can be used to match the tower to the coax 50 ohm impedance.
This subject has been discussed at length on this reflector and the
handbooks have info on the subject. 73, Dan, N5AR
Randy wrote:
>
> I'm planning to put up my tower this spring so I'm working on some of
> the details. I hope to shunt feed the tower for 80 and 160M.
> 1) I have a small city lot so my question is for the radials, I don't
> have room for any, concrete walks and bordered lawn and such are already
> in place. I do have a 4' chain link fence around 80% of the property
> line can I use that some how?
> 2) do I need to insulate the bottom of the tower?
> 3) The patio wall were the tower will go has a metal roof 15'X 20'will
> that be a problem?
>
> Randy
> AC7NJ
>
> ________________________________________________________________________
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> Order online at http://store.eham.net.
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________________________________________________________________________
Where do you get ICE bandpass filters & beverage matching boxes? The
same place that pays for the hosting of this list: The eHam Store.
Order online at http://store.eham.net.
-----------------------------------------------------------------------
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FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
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Problems: owner-towertalk@contesting.com
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