W8JI, IIRC, pointed out that if you have sufficient top loading wires to
get roughly uniform current
distribution along the vertical, then it doesn't matter where you put
the loading coil:
top, middle, or bottom. Same inductance for resonance and same
efficiency.
The top/middle/bottom argument stemmed from analyzing mobile whips that
could never have significant top load for obvious reasons.
For any 160m vertical that is guyed, it is trivial to top load it.
---
Rick Karlquist
N6RK
On 2024-07-23 18:27, Arthur Bernstein via TowerTalk wrote:
> If memory serves me correct the coil for 160 meters on the Hy Tower was at
> the bottom of the vertical. A less efficient way to get on 160. A better way
> would be to use an actual trap or a high reactance coil on top and extending
> it with wire to resonate on 160.A similar method is used by Alpha Delta on
> their DX-A Sloper. However on this antenna the resonance for 160 is provided
> from the inductance of a tightly wound coil on a fiberglass(?) coil form.
> Basically one leg is a 40 meter sloping quarter wave roughly 33 ft or so
> long, then the "iso-res" coil and approximately 18 ft extender to be trimmed
> for the narrow resonance on 160. An 80 meter elevated "iso res" might be kind
> of hefty.
> Art., N2KA
>
> Arthur Bernstein
> n2ka@verizon.net
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