Completely agree, but you didn't say how to get past the garden
committee. :>) 73, Guy.
On Wed, Aug 1, 2012 at 8:31 AM, Tom W8JI <w8ji@w8ji.com> wrote:
>> It's that thing about "at the top" that probably doesn't get past the
>> "garden committee". Folks don't really understand reactionary until
>> you've crossed swords with the "garden committee". Maybe something
>> that slides INSIDE a fiberglass flag pole.
>
> The major problem with ANY 43 ft vertical is it is nearly like a mobile
> antenna on 160. Unless the system has huge losses, RF voltages are off the
> map. With low-loss ground systems and loading coils, even the voltage
> across a base loading coil is far too high for any reasonable relay.
>
> (I know there have been articles that say otherwise, but I modeled systems
> and I actually tested several on 160 meters.)
>
> With a modest ground system, high-Q loading coil, and very good base
> insulator, and with only 500 watts applied, arcing distance for connections
> across the coil or from base to ground, was nearly one inch through
> moderately dry air at sharp points.
>
> If I wanted to run higher power with a 43ft vertical on 160, I'd just add
> two or three wires from the top that could fold in and be tied to the
> antenna at the bottom. Then, on 160 and 80, they could be fanned out away
> from the base and a modest amount of base load used on 160.
>
> Top loading with a "hat" not only gives *up to* four times the radiation
> resistance (reducing ground losses), it increases bandwidth and makes base
> voltages tolerable.
>
> Or you can just do like the original design plan called for. Have so much
> distributed loss voltages never get high.
>
> 73 Tom
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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