<This is a slightly revised version of a response I sent to Tom W8JI rather
than the list, in error> :)
In support of current baluns on the feedline....
I've had success with a Butternut HF6V vertical mounted on top of a 25-foot
tall wooden pole. There were a total of twelve resonant wire radials, 2 for
10m, 2 for 20m, 2 for 30m and 2 for 40m. The wires in each band-pair were
mounted 180 degrees apart. The twelve radials were fanned out symmetrically
around the base, with the wires sloping downward at about 20 degrees. The
40m radials provided a useable match on 15m.
The coax feedline ran straight down the pole, then ran underground about 60
feet to the shack. Nicely symmetrical with respect to the radials (at least
above the ground)
After running SWR curves for each band, I installed a current balun
(several dozen ferrite beads) at the midpoint of the vertical section of
the feedline. I then re-ran the SWRs and saw that the minimum SWR
frequencies had changed a bit on several bands. I concluded that, despite
lots of radials and good symmetry, line currents were indeed flowing
initially, so I left the beads on.
This contraption worked quite well, giving me over 300 DXCC entities
barefoot over an 8-year time span.
73
Rod Elliott VE3UW
At 18:26 06/13/05, you wrote:
>You also have to watch the feedline and mounting very
>carefully. When you use less than 10 radials feedline
>currents start to be an issue. When you use two radials it
>is a big problem.
>73, Tom W8JI
>
>----- Original Message -----
>From: "Terry Conboy" <n6ry@arrl.net>
>To: <jimjarvis@ieee.org>; <towertalk@contesting.com>
>
> > According to modeling in EZNEC, as long as the two radials
>are symmetrical
> > (180 degrees apart, same slope), the azimuth and elevation
>patterns are
> > very uniform, and the horizontal radiation cancels quite
>well in the far field.
>
>_______________________________________________
>
>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
>any questions and ask for Sherman, W2FLA.
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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