> The highest RF voltage always occurs at the farthest end of an antenna
> from the feedpoint. In the case of a shunt-fed tower with an HF Yagi
> with insulated elements used for top loading, this highest RF voltage
> point would be at the ends of the Yagi's boom (where the CX-34's 20-
meter
> reflector is). If the center of the elements are grounded, beam
> performance should not be much different and the highest RF voltage on
> 160m would now be at the ends of the Yagi's elements where no arcing
will
> occur.
>
> 73, de Earl, K6SE
Since someone could wrongly argue that voltage and arcing are the only
problem, it's wise to point out that the strap connecting the center of
a yagi element to the boom could carry a noticeable current and has to
be adequate to the flowing current.
Generally speaking, the current flowing in the jumper (or coil) is
bigger when the top loading is large, the yagi element long, and the
tower short.
On the other hand, although better if also the yagi fed element is
grounded (hairpin) in most cases there is not an absolute need to
ground it to the boom if the yagi coax runs tightly with the tower legs
and its shield is grounded at the tower base.
I know someone will now complain with balun problems....
73,
Mauri I4JMY
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