Hello Dick, your numbers are telling you that the feed point is already
inductive. A series capacitance of 344 ohms should cancel the inductance and
result in a very low vswr at the frequency of your test.
That comes out to be about 250 pF. The voltage rating will be related to
the rf power used. At 1500w, there will be 5.4 amps through the capacitor and
that would produce an rf voltage of 1865 volts rms. Peak voltage will be
about 2650 so a well rated capacitor would be needed. If made adjustable,
the voltage will go well above that number while tuning.
Sounds like a nice antenna!
73,
Gerald K5GW
In a message dated 1/17/2012 5:35:09 P.M. Central Standard Time,
RLVZ@aol.com writes:
Hi Guys,
I'm shunt feeding a 90' aluminum tower for 160meters. .
I found the 50 ohm tap point on the tower and have the shunt wire
connected to the tower at that point. At the base of the Shunt wire I'm
measuring
the following:
Rs = 51 ohms.
Xs = 344.
Q = 6
Ls = 30.1 uH.
Please advise what I need to add to this circuit... such as: a 30uH
inductor? If a 30uH inductor can I easily make one, such as: X turns of
#10 wire
with a 3" diameter?
Thanks,
Dick
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