Dear Doctor Bill,
Years ago I home-brewed an antenna tuner using a
28 microhenry roller inductor that was manufactured by
B&K and was a real piece of art: ceramic work was clean,
the roller bar was spring loaded and the wheel and coil were
silver to boot.
However, even though the parts were in pristine condition
the RF ammeter in the circuit would shudder when the roller
was actuated.
The cure was powdered graphite. "A little dab'll do ya."
However, some hours into the application the graphite would slake off
and I'd have to open the cabinet up and dust again. One of the guys at
work recommended the moly grease we used to make the motor generator
armature roller bearings conductive, and said to work it in as all that
was needed
was one molecule thickness, and "Don't touch it."
The Mean Time Between Failures increased tenfold, and I ran a Heathkit
SB-220 into a 136 foot Windom fed at the 300 ohm point with a 3KW
balun coil, so it had plenty of chances to heat up.....
'73,
Hal
KA1XO/4
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