About knobs for the air variables:
I have used 1/4" diameter spacers that have 2-56 threaded studs with
that type of capacitor.  Just screw the spacer into the cap with a
little locktite and use a regular 1/4" shaft knob.  Beware that excess
locktite may attack the plastic of the capacitor body.  Also I usually
use a panel bearing for the shaft to reduce stress on the capacitor
body.

Sherpa Doug

> -----Original Message-----
> From: Mike Kendall [mailto:ke6cvh@THE-I.NET]
> Sent: Thursday, August 09, 2001 9:45 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: EE: varactors vs. air variable caps and LED windows
>
>
> Have a project I've been working on for months  now.
> 1st question-  What is a good  source for the plastic used
> for LED windows
> for the red 7 segment LED's?
> 2nd question-   Polling for input on Varactors vs air
> variable capacitors.
> I recently purchased 16 RF tuner capacitors at $1.25ea from Electronix
> Express only to find that there is no such thing as a mating
> knob for them
> in the USA (they have two flat sides on the tuning shaft and
> a threaded hole
> in the center of that.  Also, the shaft is extremely short).  I've
> considered using a varactor tuned oscillator circuit with the
> 120pF variety.
> Saw a web page that uses two varactors chained together with
> the tuning
> voltage at the  tie point.  The circuit web page mentioned
> the low Q of
> varactors and  I'm  concerned about this affecting my circuit
> negatively.
> I'm aware of homebrew amateur 2meter transcievers using
> varactors and their
> usage in radio receiver tuners.
> Regards,
> Mike
>
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