[AMPS] Inductors
ToddRoberts2001@aol.com
ToddRoberts2001@aol.com
Tue, 18 Dec 2001 04:17:10 EST
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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