Topband: Helically wound vert

[DAVID CUTHBERT]

For the 5BTV on top band the radiation resistance of the 22' top loaded
vertical is about 3 ohms. The RM80S "resonator", or top loading inductor
loss is 20 ohms (that is high). Given a GND loss resistance of 20 ohms the
radiation efficiency is 7%.

Using a homebrewed top loading coil having a Q of 300 and a larger top hat
(72" rather than 48" spokes) the radiation efficiency is 10%.

For 22' and $220 it provides usable efficiency and bandwidth in a compact
package.

     Dave WX7G

On Fri, Jul 17, 2009 at 10:28 AM, Roy <royanjoy at ncn.net> wrote:

> "Radiation efficiency is around 60% on 40 meters, 20% on 80 meters, and 7%
> on
> 160 meters. For a 23' vertical this is not bad."
>
>
> Over all system efficiency depends upon effective ground system resistance.
> Typically that would bring it to more like 2% on top band.
>
> Roy,   K6XK
>
>
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