[600MRG] Vacuum variable capacitor, low-pass/band-pass filters

[lstoskopf at cox.net]

A totally uninformed answer...   I have several small, cheap caps that have a floppy dielectric film floating between the plates.  Not exactly precision caps, but small.  I wonder if the effect of air-plastic-air is similar to a small cap-large cap-small cap in series unit so not worth the effort or stability.  If it works you would think that some of the guys selling large loop antennas would add some plastic to their heavy variable caps.  Looking for the guys that know!
N0UU 
> But why can you not take a regular large bread slicer variable, and fill 
> in the air gaps with a dialectic material. Gets two advantages
> 
> the arc over voltage point can be raised considerably!
> 
> and the amount of capacitance can be raised many many fold depending on 
> the dialectic. some insulating plastics can be like 15 times!
> 
> Why is this not done ever that I have seen?
> 
> Joe WB9SBD