Protects your stuff from EM radiation and stuff, but is this really a concern in e.g. a PlayStation 2? Are they a relic from the past? Is there any proof of them harming electronics?
In: Technology
Back in 90s early 2000s I knew my cellphone was going to ring because my speakers would make noise. The vacuum would mess up the TV picture. I remember we had something to close to a old plasma TV and turned the corner purple. So some reasons.
The shielding is to prevent unwanted emissions of RF. Devices need to be tested and certified by the FCC.
If they could get away without the RF shields they would have. A lot of things in electronics involve switching power on and off very quickly. For example the processor and graphics chip is constantly switching at its clock frequency in order to do calculations. So for every clock tick there is a huge power draw. Modern more powerful processors have even bigger power spikes. The current going through the wires like this makes the wires act like antennas.
And if you think about processor clock speeds they might often end up in the 2.4GHz range which is used for WiFi and Bluetooth. I have seen laptops with inadequate RF shielding lose WiFi signal at specific processor loads. And while most processors can not get up to the 5GHz band there are harmonics which can disrupt even this band. And then you have the new 6GHz band used by WiFi6 where other harmonics can reach. And then you have cell phones which use a number of frequency bands like 600MHz, 900MHz, 1.7GHz, 4.7GHz, and up. If your electronics is not shielded it will disrupt traffic on these bands.
It also goes the other way around. If your cell phone receives a call and therefore outputs a lot of radiation, something you might have heard through poorly shielded speaker cables. Then this signal will get picked up by the wires to the processor and if there is some harmony with the clock frequency it may disrupt the processor, most likely causing it to crash.
Every home electronics device is tested. They put it inside a chamber that blocks any RF interference from the outside. And then they test how much radiation it puts out on all frequencies. If it is lower then the legal requirements it passes. And then they test it while bombarding it with radiation at various frequencies and check if the device fails in any way. If the device is passes this test the engineers go inn and remove some of the shielding trying to make it cheaper to manufacture, and then they redo the test. They want to get away with as little shielding as possible. But usually they need extra radiation shielding between the processor, graphics card, WiFi module and power supply as these can interfere with each other due to their close proximity. But the engineers also have to take into account that people may leave their phone on the device or even connected to the USB port to change. So they need proper RF shields to the environment.
The government has very strict regulations on the amount of electromagnetic noise that a device can emit. This is to ensure that your electronics don’t disrupt the function of other devices.
The metal shields help to reduce emissions from noisy subassemblies in the unit – usually a switching power supply or processor. [source: part of my job is to take consumer electronics products to FCC/CE testing labs]
The shields are not there to ‘protect’ the electronics from radio frequencies. They are there to prevent interference. Things like video and audio outputs are very susceptible to radio frequency interference and would produce things like static/pops in audio and visual imperfections in video. The shields reduce these impacts.
You remember old TV-s and radios making weird noises when a cellphone next to them got a call? Yeah, radio frequency interference is a thing. But if a piece of analog electronics just makes a funny noise, then the same funny noise in digital electronics is complete nonsense data that does not compute. That can in some extreme cases just brick devices if it gets saved instead of data that was supposed to mean something.
they do the same thing as a “tin foil room” also known as a miniature faraday cage.
they keep the electrical noise inside the cage.
or they keep noise out of a sensitive circuit.
the fcc rules have two classes of things: an intentional radiator, and an unintentional radiator
an intentional radiator is like a wakie-talkie or cellphone or wifi device it is suppose to transmit intentionally.
a radio, like the one in a car to play music or to listen to the news or your television is not purposely transmitting (radiating rf signals) but it does any way.
some times to stop or shield this you put it inside a metal box
when i was a kid i had a trs80 model 1 it ran at about 4mhz, my room was next to the living room. when i turned on the computer the damn color on the tv went bonkers.
this was a problem because on sunday my dad wanted to watch football, and i would goto my room to play on my computer.. and the tv went crazy so bad that my dad forbid me to use my computer when the football game was on.
later versions used a copper based paint on the inside of the computer case, but i had an early one that did not have this special paint.
I make electronics and our org tests everything for em interference. When they fail, it is sometimes really obvious. Have a thing with cap touch buttons? Noise makes phantom button presses and turns your shit on and off at random. Com protocols? Half your messages just drop and you have to slow communications or just never get messages.
So we upgrade the hardware and firmware to handle the em so our gear doesn’t suck ass.
In most cases the RF shielding is actually not to protect that device but to keep that device from interfering with other devices. It is required to be limited so that it doesn’t interfere with other devices under federal law.
Pretty much any modern electronic device transmits information over wires internally at one frequency or another.
How do you create a radio transmit a signal over a wire. So basically all of these devices give off some EM/RF.
[https://transition.fcc.gov/oet/info/documents/bulletins/oet62/oet62rev.pdf](https://transition.fcc.gov/oet/info/documents/bulletins/oet62/oet62rev.pdf)
[https://www.fcc.gov/oet/ea/rfdevice](https://www.fcc.gov/oet/ea/rfdevice)
“This device complies with part 15 of the FCC rules. Operation is subject to the following two conditions: (1) this device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.”
That is probably one of the worst worded statements. By accepting interference all it means is it won’t try to interfere with the outside transmission. You could operate your device in a Faraday cage and ground it. The chassis could do that. That would be legal. It would accept outside interference that way without interfering back. It is just grounding that interference.
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