I have just had a chat with a friend who is working on a very high gain amplifier and had a lot of trouble with shielding whilst testing. He seems to have come up with a simple method to do this by going to his local rubbish tip and picking up a scrap microwave oven. He removed all the microwave parts, and fitted an access panel where the magnetron fed into the cooking cavity, it is an aluminium plate with BNC and bannana plug sockets to which on the outside he connects power supplies, and the inside, probes and connectors etc.
He says that he does not use the lamp but illuminates it through the door window.
So far, it has enabled him to carry out tests that otherwise would have been almost impossible.
It reminds me of when I worked at a communications company working on military equipment, we had a Faraday screened room.

 

A clever solution but wouldn't it sill be vulnerable to other frequencies? I mean, a microwave shell is designed to reduce microwave emissions by 1000X or whatever. Maybe a million fold. But they don't worry about other frequencies.

 

Stick a dab radio and your mobile phone inside and see what you get

 

The sheetmetal chassis takes care of most other frequencies.

Consider it stolen intellectual property

 

The screen holes on the door window will let through frequencies that have a wavelength smaller than the hole size, but it should efficiently screen out any electromagnetic waves at or below the microwave oven frequency.

 

The door seal in a microwave is designed with a choke joint for ~2.45 Ghz not a wide band of frequencies. It's not a conductive metal to metal seal needed for a good wide-band RF Faraday cage. YMMV with the frequency.