At 11:59 PM 9/11/2008, Gene Smar wrote:
>Another item you need to be aware of: all elements of an LP are above
>ground. Therefore, they are not suitable for top-loading a tower for use
>on the lowbands. They also represent a different lightning risk than a
>grounded-element design. FWIW.
Just a small quibble, because I agree with everything else that Gene has
mentioned - my yagis are all insulated element Force-12 designs, and they
work just fine as top-loading on 160 at low power (~200 watts). There's a
risk of flash-over on the top antenna when used this way with high power,
which W8JI suggested could be mitigated with RF chokes of the proper size
from the element to ground, which would effectively ground each element at
1.8 MHz. In this respect an LPDA would be easier to deal with than an
insulated-element Yagi, which would require the chokes at each element.
73, Pete N4ZR
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