Inside an Early Microwave Cavity Filter (250MHz - 1GHz)

A look inside an RF cavity filter salvaged from a trash pile
#CavityFilter #RF #Microwave
Thumbnail Credit: Francis Fletcher

[@orbitingeyes2540]

Most likely reason for the mismatch and variation in insertion loss is that the coupling probes don't scale as you tune the cavity.

[@lordgarak]

Late comment on an old video. But that thing is measuring as if there is something really wrong with it. Cavity filters should only have a few DB of insertion loss and have a much lower return loss. My guess is that one of the coupling loops is broken.

[@RobertResearchRadios]

Hmm maybe a connector with a bad contact? I have no intuition for insertion loss on cavity filters so didn't notice it might be broken, but I can't see broken loops from the video at least. Maybe I'll take another look inside it someday. Not sure where it's gotten off to, but the insight of a "simple tailor" is appreciated good sir.

[@TheOpticalFreak]

Wow 😮 that is so cool! 😃👍

[@michael.wilspang]

What is the name of the manufacturer and p/n of this filter?

[@egbertgroot2737]

Interesting ..... always wonder how using a transmitting tube like the 2c39 this cavity is put on top of the anode ..... and still works ....

[@masonjohn4433]

Do you know of a good resource that talks about how to design these? Most of the microwave engineering textbooks that I have found contain only a few paragraphs on cavity resonators.

[@jeremycole3008]

wonder if you could use this thing for frequency modulation slope detection across this frequency band?