In a differential capacitor, as the rotor disengages from one
set of fixed plates, it engages with the other set, instead of
engaging with fresh air.

The two sets of fixed plates are adjacent to each other and
separated by a gap. (If it were not for the gap, there would
be a solid square of metal with the axle dead centre)

"Mike, K8LH" wrote in message
...

RG, is there an example of a differential capacitor I could look at? I'm
not sure I've ever seen one? Is there a Tuner project somewhere using one
I could look at (grin)...