A screwdriver antenna is a continuously tunable motorized vertical
antenna.
Picture a 3" aluminum pipe, about 4 feet long - inside that pipe is a 2-
1/2 inch diameter by about 18-inch long PVC (or other non-conductor)
tube, wound with approximately 120 feet of 16-guage solid copper wire.
At the base of the PVC pipe is a threaded rod, which runs nearly to the
bottom of the length of aluminum pipe, where it connects to a cordless
screwdriver motor, wired for remote operation. These motors can reverse,
so if you have a nut connected at the base of the PVC, you can extend or
retract the coil from within the pipe.
On top of the coil, place a 102-inch whip antenna - there you have it -
run the PVC up and down to resonate the antenna pretty close to 1:1 from
10 - 80 meters - more if you play a little. It's a little more complex
than that - but not much.
- Jim
zeitler@ibm.net wrote:
>
> It has been recommended by more than one ham to go with the screwdriver
> antenna for my portable vertical project. What the heck is a screwdriver
> antenna??
>
> Lane
> KM3G
> San Diego
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