I have a question, unless there is a "slit" cut
down one side of this copper tube wouldn't it
(the copper tube) also act as a shorted turn?
Mark WB8JKR
On Tue, 18 Dec 2001 04:17:10 EST ToddRoberts2001@aol.com writes:
>
> I think the most efficient variable inductor I have seen is one
> based on the
> "screwdriver" antenna. A coil is placed inside a copper tube of
> slightly
> larger diameter. At one end of the copper tube is a ring of
> heavy-duty finger
> stock that contacts one turn of the coil. As one end of the coil is
> rotated
> on a threaded shaft the other end of the coil emerges from the
> copper tube.
> The turns inside the copper tube are completely out of circuit as RF
> flows on
> the outside of the copper tube. This eliminates the lossy "shorted
> turn"
> effect that is present on standard roller inductors. I am waiting
> for someone
> to apply this technique to high-power transmitting inductors for
> amplifier
> use. 73 Todd Roberts WD4NGG .
>
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