Confinement box in the resonator ruins result

[yefj]

Hello , I have built a resonator as described in the photos and the link in the video below.
Basickly each coax cable excites a mode in the dielectric saphire cube shown below.
However I need to confine the whole system in a metal box where both exitation connector so outer coax coating connected to the box as shown in the end .
As I do that I get a tottaly different resonance map I get many many spike of resonanse in stead of the original.
I Know that the metal box add lots of capacitance . Is the a way to minimize the effect of the metal box so the resonance will be as if the is no metal box?
Thanks.
2026-02-04 13-49-21.mp4

 

[.Scott]

I suspect your problem is more of a wave guide problem than capacitance.
With a 3cm wavelength, your "ground" level will criss-cross the surfaces of the box every which way.
I would use dual-coax, ground the outer layer to the box and use the inner layer and the core for your resonator.