[TowerTalk] finding resonant frequency of a shunt-fed tower for 160

[N2TK]

Hi Pete. One time I dropped a wire from the top of the 80' tower, about 1.5'
away from the tower. I grounded the bottom end of the wire to the base of
the tower. About 3' from the bottom I put in a small loop. With a grid dip
meter, I got a dip at 1.3MHZ. Not sure what that was really telling me.

After this I tried hanging a 80M delta loop about 15' from the tower. Where
I had the grid dip loop, I installed a broadcast type variable cap. I could
change the resonance of the loop from cw to phone by varying the variable
cap. I guess I had some interaction - hi.

By the way, at this location I strung a shunt wire about 2' from the tower.
It ties in to the tower at 70'. The bottom end attaches through a series vac
variable at 15' up from the base. Tunes to a low swr. I have 4 elevated
radials. The antenna almost works. Maybe will get time this summer to put
down some radials on the ground, but the damn deer keep pulling up that
stuff over the rocks. I wonder if it matters if I leave the shunt feed 15'
up when I take down the elevated radials and go with ground radials?

Tony

-----Original Message-----
From: owner-towertalk@contesting.com
[mailto:owner-towertalk@contesting.com]On Behalf Of Pete Smith
Sent: Monday, July 30, 2001 11:34
To: towertalk@contesting.com
Subject: [TowerTalk] finding resonant frequency of a shunt-fed tower for 160


This is my ignorant question for today -- with only an antenna analyzer,
how can I determine the resonant frequency of my tower?  I plan to attach a
first-attempt at shunt feed at about the 30-foot level, with 30-inch
spacing from the tower.  Can I tell from the analyzer reading at the bottom
of that shunt wire where the tower is resonant?  Do I need to put the
series capacitance in before attempting the measurement?  Or is it all
fruitless?

Clearly my education was neglected or I'd know the answer, so thanks for
your help and patience.

73, Pete N4ZR







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