I made this 80/40 meter vertical and would like some feedback on the ground
I installed.
The ground here is very good. Loamy soil for as far as the eye can see --
corn and beans mostly.
I used what the locals here in MN call "cattle panels." It is made from
16' - 1/4" rods, spaced about 6" apart and welded into a grid of sorts. It
is very hard stuff -- like 1/4" spring steel. Each junction is welded. The
panels are 54" x 16' long and 6" grid.
I placed a 54" square piece right over the post used to support the weight
of the vertical. 1 - 16' panel was then placed at each edge and welded
together to form an "X" shape around the tower. An 8' copper clad ground
rod was placed right at the base of the vertical and welded to the panels.
Flat washers were welded to the panels too. These act as ground connections
for the vertical -- both the 80 main vertical and the 40 meter sleeves.
After a few weeks of laying on the grass, I can't even see the panels any
more (two mowings).
I am getting a feed point impedance of 45 +j5 at 3.5 mhz. 44 +/-j0 at
resonance. It is roughly the same on 40 meters (resonant sleeves are
spaced 18" off the main tower). The 40 meter impedance is not meaningful
for my question because the impedance is adjustable by changing the spacing
of the sleeve -- closer is lower R, farther is greater R. The main vertical
may help me predict the quality of my ground.
My question is this: Mininec 3 predicts (perfect ground for impedance
measurements) a feed point impedance of 36 +/- j 0 at resonance. Am I to
assume then that there is about 8-9 ohms of ground loss? If so, is this
good, average, or poor for a full sized vertical? I have never had
experience with insulated verticals before and have no basis for judgement.
I turn instead to the hundreds of years of collective experience of the
towertalkians--the singular repository of all knowledge (RF).
Thanks for the bandwidth.
Ford-N0FP
ford@cmgate.com
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