I have a 48 foot free standing tower. At the top is a Cushcraft A3S
3-element tri-bander with the 40m add-on kit. About 5 feet above that is
a 3-element 6m beam. About 2 feet above that is a 2m/440 vertical. Also
at the top of the tower about 1 foot out is the apex of a 80m inverted V.
On the opposite side of the tower from the 80m inverted V is my shunt
wire. It is attached at the top of the tower and runs the entire height
of the tower. It is about 18 inches away from the tower. It is a single
14 gauge stranded wire.
There are 46 65' radials at the base of the tower spread out over 180
degrees from north thru east to south. The area to the west of the tower
is blocked by the house so I can't put radials there.
I have been unable to get any kind of reasonable match on this setup.
I've tried a variety of variable capacitors and coils in various
configurations with no luck.
Connecting my MFJ-259B to the shunt wire and ground and adjusting for 50
ohms of resistance, I get a frequency of 9.145 MHz, R=50, X=46, and SWR
Setting the frequency to 1.8 MHz, I get a R=0 (it seems to stay at zero
no matter what frequency I set it at until I get close to 9.145 MHz),
X=637, and SWR = >25.
To be honest, I don't really know what these numbers are telling me. The
folks who taught me to build antennas only looked at SWR. Low SWR good
to go. None of this R and X stuff. I suppose with dipoles one might get
away with this, but this antenna seems to be a different game.
I'm looking for some ideas on what direction to head. I'm open for any
suggestions. Is the wire too close to the tower? Too far away? Do I need
more wires? Is this tower configuration just not suitable for a shunt
fed antenna? What additional data might you need to determine what's
going on here?
Thanks for any input you might have,
-- Kelley - WØRK
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