Custom case question - mesh panel design to minimise interference

[timginter]

Does anyone know if mesh panels need specific "hole" sizes and if mesh panels help with interference? I have a custom portable PC https://smallformfactor.net/forum/threads/diy-laptop-portable-pc-5-4-litres-17-screen.15795/ but interference is really bad. From my tests it looks like the GPU riser. I tried different cables, same problem with all, ADT ones seemed the best. I moved the WiFi antenna and that solved my signal problems. The USB hub in the front sticks out slightly - that helped with wireless keyboard and headphones, but, e.g. if the keyboard is at an angle where the signal goes "through" the case, some keypresses do not register or register with a delay. Same with headphones - crackling, sounds drops, etc. I'd gladly tinker a bit and improve the design.

I checked https://smallformfactor.net/forum/t...l-mesh-sff-tower-11-9l-280clc-no-riser.13694/ , https://smallformfactor.net/forum/t...-78mm-cpu-height-mesh-panels-13-7l-itx.16167/ , https://smallformfactor.net/forum/threads/jonsbo-shows-vr3-mesh-tower-itx-sff-case.17183/ (absolutely beautiful), but they all seem to have different mesh designs.

I searched for info in https://smallformfactor.net/forum/resources/categories/enclosure.3/ but couldn't find anything mesh-related. May have missed something, though.

I also checked https://www.protocase.com/resources/how-to-design-for-motherboards/ but that's more for cutouts and mounting of motherboard.

I thought adding mesh panels on the sides will keep the interference inside - is that what a normal PC case does? Can it be because of my design? Nothing separating the GPU and everything sandwitched between 2 aluminium plates? I haven't tried taping aluminium foil to each side, but that would kill the cooling. Most open cases have either the GPU in a section separated by a metal plate from the rest of the hardware, or a totally open design without any side panels. I'm really surprised any info on interference is so hard to find on the net in general.

I'd really appreciate any info, there's a lot of knowledge on custom cases here. Would mesh panels even help? I'd probably test with thick, perforated aluminium foil first, but wonder if the holes have to be of certain size to trap specific wave lengths, like in a microwave door... or maybe I'm overthinging this totally

 

[msystems]

It sounds like your problem is with bluetooth signal not reaching the keyboard. If the case is acting like a Faraday cage, possibly relocate the rf transmitter stuff to the back of the monitor on ribbon extension cables so it is outside the case. Then use vhb tape to secure it.
You could also look into integrating 3d parts into your design, they won't block the signal as much.

Regarding those little holes, they aren't large enough to allow 2.5ghz rf thorough. Im pretty sure no case can, which is why we've got external antennas and our Bluetooth stuff sticks out the back of the io shield outside of the case. Bluetooth and wifi is like 12cm wavelength, so basically need one side completely open not to block that.

 

[timginter]

It sounds like your problem is with bluetooth signal not reaching the keyboard. If the case is acting like a Faraday cage, possibly relocate the rf transmitter stuff to the back of the monitor on ribbon extension cables so it is outside the case. Then use vhb tape to secure it.
You could also look into integrating 3d parts into your design, they won't block the signal as much.

Regarding those little holes, they aren't large enough to allow 2.5ghz rf thorough. Im pretty sure no case can, which is why we've got external antennas and our Bluetooth stuff sticks out the back of the io shield outside of the case. Bluetooth and wifi is like 12cm wavelength, so basically need one side completely open not to block that.

Thanks! But Bluetooth is on the network card, wouldn't it be handled by extension antennae at the top of the monitor? When antennae were screwed directly to the WiFi card, close to the motherboard, WiFi and Bluetooth were very flakey. Keyboard and headphones have 2.4GHz dongles, both are plugged into the front USB hub. When I plug them into the back IO, on the motherboard, sometimes all is OK, sometimes nothing worked at all.

My guess is that any interference waves are bouncing between the aluminium plate and the only way to escape is through the open sides, messing with other electronics.

Sounds like I need a Faraday cage, but to keep the interference inside, with other waves bouncing around the case

 

[msystems]

There is rf tape / shielding which is exactly that, and you could give it a try

 

[timginter]

There is rf tape / shielding which is exactly that, and you could give it a try

Not sure what you mean. Tape the sides of the case or tape the riser where I suspect interference is coming from?

 

[msystems]

you could try it on the riser, and also using it to shield the 2.4g signal path. I would try shielding the rf antennas until they reach the back of the case. No idea if it would work but the roll of shielding tape has quite a bit of tape, enough to experiment and see what works. you could also try swapping antennas and try replacing the antenna wiring with a new set

 

[timginter]

you could try it on the riser, and also using it to shield the 2.4g signal path. I would try shielding the rf antennas until they reach the back of the case. No idea if it would work but the roll of shielding tape has quite a bit of tape, enough to experiment and see what works. you could also try swapping antennas and try replacing the antenna wiring with a new set

Thanks, but I don't have WiFi problems. I don't know what you mean by shielding the 2.4GHz signal path with tape.

I already found solutions - I already extended WiFi antennae and mounted them on top of the monitor - it's not a problem. The USB hub solved headphones and keyboard issues. The only problem is, e.g. when "lapdesk" is turned so that I'm behind it - then the "case" seem to interfere with the keyboard and headphones signal.

I just wondered if anyone had similar problems or if the usual PC case design traps interference inside and keeps IO signals out and around the case. If yes, then mesh side-panels for my lapdesk would solve any interference problems