As part of the NLNet grant, I will build an affordable Faraday cage; I'll post the BOM, assembly process and a test report in a separate blog post.

I am researching that at this time as well. I have VNA etc and am keen to collaborate !

[email protected]

I have quite a collection of research material on RF cages / testing .

There is an email address at the bottom of the blog post, you can send directly there.

We needed a large highly isolating cage for a project and the cost-effective (but still costly) way to do that was to build our own, having local welders make a custom steel box and lining it up with rf anechoic pyramid foam, otherwise the reflections make weird RF noise. A tricky part is the seams where your doors meet the box. It's easier to get good isolation from outside if you don't have to connect any wires, i.e. if any "control" you need is done by a battery-powered computer (laptop or smartphone) inside the isolation.

Based only on my own anecdotal experience... I think the hole the cables go through is the biggest problem in OPs setup. I'd solder the shields to the cage circumferentially around the hole. Shielded USB cables aren't too hard to find, it wouldn't be as good as something optical but it's a lot easier.

Feed through capacitors for power and use fiber for the rest?

If power was really the problem I'd just use a battery inside the cage.

Related, this is a neat experiment which powers a galvanically isolated circuit optically using LEDs and a solar cell: https://youtu.be/9JinSfCKuNQ?t=823&si=kBwesUsVgAGBVVwq

He didn't need to block RF though, the interface seems mechanically challenging to build into a cage.

I used the isolation „fabric“ wrapped around the extension cable off a super cheap PCIe riser card. I put an iPhone inside which blocked WiFi, BT and 4G.

Not directly answering your question, but on preventing emission in the first place (and the best video I've ever seen on electrical engineering): https://www.youtube.com/watch?v=ySuUZEjARPY

Lots of very useful information here, thanks for the link! Actually there's some answer: as someone else already wrote in this thread, shields of cables must be soldered to the Faraday cage to prevent leakage.