Been working on getting the 160 meter antenna situation figured out before
the WX gets too bad. I have decided on using my 105 foot tower that has
a 3 element 40 on the top (and some other antennas on the way up and a
six meter beam at 115 feet).
I tried using a reverse feed on it briefly last year and it seemed to work
fairly well. This year, I am doing it "right" and trying to use the trap
method shown in the ON4UN book to keep current from coming down below the
feedpoint (which is up around 40 feet).
I ran a piece of 12 guage wire out about 18" from the tower down to the
ground. I made a current meter out of some ferrite - a few turns on the
secondary and a 150 Ohm resistor. Used a scope to read the level.
I had a 1000 pf variable cap. I saw a big peak in the current between the
CAP and tower around 300 pf and then it just kind of goes down as I keep
increasing the capacitance. I tried some parallel capacitance, but other
than a general decrease in current as I increased the capacitance, I don't
seem to have a sharp null of any kind.
I was wondering why kind of capacitance values people have used for this
application - and if they were able to produce a null of some kind where
the current went down to about zero.
Tree N6TR
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