[negative_zero]

That was not my read on it. My interpretation was that they wanted to sell a product, but didn't want to pay for an engineer who understands all this, labs for testing and doing all the paper work that it entails. So the plan became: "Customer buy this software, buy that hardware and put it together" => not liable => profit.

"Is this not exactly equivalent how I might buy a Raspberry Pi and install a non-Raspberry-authorized OS on it? Or equivalent on how I might buy a PC and install Linux on it? Or Android and LineageOS? Are those devices certified not only as SOLD but also as modified by the end-user with software, making them somehow different?"

Yes and no :) Very very succinctly: When you test and cert, it is best practice to create the worst case scenario for your product and pass like with healthy margins. Especially for something like a smartphone or PC, when it's in the test chamber (for something like radiated emissions), you run it at "full noise" (even if it's not a realistic use case). So all your clocks: maximum (don't use all of the clocks? Turn them all on anyway); Power draw: Maximum or more; Play seizure inducing video to exercise that screen; Connect peripherals that are likely to be used to make sure those don't screw you etc. PCs and phones, especially, are tested at these extremes so that the manufacturer can be confident that despite what software the end-user loads, the device will remain compliant (this is also why the radio firmware is kept locked down hard).

Now in the case of this article, sure, the dev boards have CE, but what does that mean? How did they test it? Where all the peripherals running? What did the physical test setup look like? Under CE they are required to keep a compliance folder and to provide the information on request.

My experience with, dev boards that are "compliant". They just powered it up and maybe ran a simple program. Low effort, low noise, easy pass, because the reality is that they don't need it and time is money.

So now you a third party integrator takes that dev board, and runs something that wasn't exercised or puts it into a state that is non compliant. That's on you. Just like it's on the Author of this article.

I might be wrong in this case. Maybe the dev boards have excellent test setups. I might look at the test docs and think: "oh we should be fine". And just do a pre-compliance test and self-certify. You have to evaluate the risk each time and make a call.

If Microsoft released a patch tomorrow that somehow caused a sizable percentage of PCs to start stepping on the cell phone bands they would VERY quickly be told (I emphasise told NOT asked) to fix it. Just like any software this Author could load. They have not sidestepped any responsibility.

[_flux]

I was actually under the impression that PC motherboards have the spread spectrum clock available exactly for compliance reasons, and indeed it's the default as well. But you can turn it off.

Maybe they do indeed test without it, and it's only for the benefit of integrators to make use of (and perhaps disable other options altogether), if they find their complete system emissions somehow exceed limits.

Now that I'm in position to ask ;), I've wondered about the glass/plastic window PC cases.. Surely a PC case itself would not be required to have any emission tests done on it, or would it? On the other hand, might the PC motherboard emissions be certified with the assumption that it will be placed inside a case?

And then finally comes a consumer (or even a small integrator) and sticks in a PC motherboard inside a windowed case—but in this case the case might not be doing much on the RF side. Or maybe the cases provide better RF protection than they look like or the MBs don't need a case for that reason in the first place :).

[negative_zero]

You are correct on the spread spectrum clocks. Outside of military, they really soley exist for compliance (specifically unintended electromagnetic emissions) and are increasingly everywhere out of necessity. If an integrator needs spread spectrum locked on, there is no doubt a BIOS available that does just that.

"Now that I'm in position to ask ;)"

Ask away :) This is boring for 99.99999% of the population so I don't get to talk about it often :)

"I've wondered about the glass/plastic window PC cases.. Surely a PC case itself would not be required to have any emission tests done on it, or would it?"

You're right, a PC case itself does not need EMC compliance, but a PC case that's sold with a power supply does. So does one with built in fans and lights or anything electronic. IMO and very much off the cuff, certing the case + lights and fans without a whole computer inside is probably reasonable. But I would personally try cert with a whole PC (defence in depth).

"On the other hand, might the PC motherboard emissions be certified with the assumption that it will be placed inside a case?"

Yes it can be certed that way. Generally if it is, the details have to be in the manual.

But also, legally, you don't really need to cert a motherboard because it will always be integrated into another thing. However the reality of the PC architecture is that it is extremely modular and reach module is extremely complex. It's simply not at all practical for any systems integrator to try to modify those modules to try and make a whole PC compliant so that they can sell it. Even sticking the whole thing in a metal case might not be enough because the case has cables attached to and unwanted emissions and get out via those.

So for practical purposes manufacturers of motherboards, graphics cards, PSUs, hard drives etc vigorously test and cert their products with decent margins so that no matter what cards are used or how a PC is put together, the sum will be compliant. And this rule holds pretty well in general at all scales, from the individual parts and submodules that come together to make a product up to several products wired together in your house with power and network cables.

And system integrators can demand these requirements because it's necessary for the industry to function. I found a few years ago on Dell's website their manual for part suppliers. It listed every standard they required, made stricter and even had additions of their own so that they could sell with your module everywhere in the world, because they sell everywhere. It basically a thick manual on making a computer "world compatible".

"And then finally comes a consumer (or even a small integrator) and sticks in a PC motherboard inside a windowed case—but in this case the case might not be doing much on the RF side. Or maybe the cases provide better RF protection than they look like or the MBs don't need a case for that reason in the first place :)."

And the consumer benefits from everything I explained earlier. They can buy parts and assemble a computer that will be compliant. It's also why computer shops can build you a PC and sell without a cert and it'll be fine. Just the sheer effort of all these manufacturers so that they have a market to sell into means that the problem is solved for small players in the traditional PC world. The traditional PC industry is quite unique in that way actually.

[HeyLaughingBoy]

That bit about PCs and phones was surprising, but I guess not unexpected. I have built many "EMI test versions" of code so various products can be taken to the test house. We don't go to those extremes: typically, we'll run as close to worst case as we can get, but nothing unrealistic. Then again, no one but us is loading code onto our devices, so it's not like a PC where you have no control over what it's running.

[negative_zero]

One company I have worked with had an internal rule for "radiated emissions": You had to be 10dB (1 order of magnitude) underneath the limits before going for a formal cert. Non-negotiable.

Part of the reason for this rule was that they:

1) OEMed their products.

2) Sold products that could be used in complex and bespoke CAN networks with goodness knows what else.

3) There was a chance of interfering with Marine VHF radio which is used for emergencies. The EU rules were (still are) not actually strict enough for preventing interference with that band.