N2EA writes:
> A question for the modellers might be...what would the effect
> of feeding the tower be on radiation pattern? I'd expect it
> would be different for each band.
You are correct ... it will also vary based on the height of the
tower (of course). Where the tower is "short," or near 1/2 wave
electrically, it will represent a low impedance connection and
considerable current will flow in the tower causing radiation
and perhaps upsetting the vertical tuning. Where the tower is
"long," or near an odd number of quarter waves electrically, the
tower connection will represent a relatively high impedance -
minimum ground current will flow in the tower and it will have
minimal impact on the vertical.
By the way, the same issues occur with the feedline! Any elevated
vertical really needs a good current choke at the feedpoint to take
the shield of the feedline "out of play." Otherwise the entire
system can act like an off-center fed vertical longwire with many
high angle lobes and unpredictable response.
73,
... Joe, K4IK
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