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 <[email protected]> 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 _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
