[zsellera]

As someone recently participated in an EMC measurement, I really don't understand how anyone passes these tests without some kind of cheating (using double-shielded, very expensive industrial cables + hacking with functional earthing).

[avian]

I've spent months and sleepless nights trying to get a product through the EMC certification. It's certainly possible but it's time consuming and expensive. With a shoestring engineering budget and a product that needs to be on the shelves in a month? Not really.

I'm sure many devices on the market are not compliant. I follow lists of products removed from market for non-compliance and there are plenty each week. But the fact is that, if you're not in one of the categories that are under special scrutiny (aerospace, automobile, medical, etc.) or do something grossly incompetent (e.g. interfere with a mobile operator or someone else with a similar power to put you into the regulatory spotlight) you're unlikely to get into trouble for shipping a non-compliant device.

Make someone's Wi-Fi a bit slower and a bit more packet-lossy? Chances are nobody will care. It's a sad state of affairs really because pervasive radio interference is just making things worse for everyone.

[semi-extrinsic]

Yeah, I remember in the early 2000s we had a wireless RCA audio/video transmitter, bought at a local electronics store, that played absolute havoc with the WiFi in our house as well as several neighbours.

Another classic example is early cellphones that you would pick up on stereo systems etc. - "dat-dara-dat-dara-dat-dara-dat-dara-daaaaaa" going out in full blast.

[jcrawfordor]

Because those A/V transmitters used the same 2.4GHz ISM band as WiFi at the time, there was actually no regulatory protection against this interference - from a regulatory perspective it's just a normal and expected part of using an ISM band where there is no protection. The increasing popularity of WiFi started to really surface the problems in this area, similar issues are seen in 900MHz far less often because it's mostly used with low-power, low-duty-cycle devices.... the same as was intended for 2.4GHz before widespread consumer WiFi.

[jimmaswell]

In GTA 4 (set in the early 2000s or so) you hear that on your car stereo before your phone rings. I always loved that detail.

[Johnythree]

Unfortunately both examples are misleading:

Unlicensed equipment in the ISM WiFi band are operating under Part 15 (in USA) so must accept any interference.

And the phone interference to a stereo is caused by cheap and nasty design of the stereo. The phone itself cannot be blamed, and there's nothing which can be done to the phone to fix the interference (other than switching it off). Again the stereo is probably operating under Part 15, so must accept any interference.

[avian]

The effect of GSM phones on analog audio equipment was actually an oversight in defining the standard. Fully compliant equipment had that effect.

Some years back when I had some small involvement in new EU regulations that case was actually given as an example of how, even after many reviews, some forms of harmful interference can only become apparent after a technology is already widely deployed.

[Johnythree]

No, the interference from GSM is caused by poor immunity in the audio equipment. You can't blame the EU standard for crappy analog audio equipment.

The RF breakthrough is caused by the Amplitude Modulation in GSM, but then there's nothing fundamentally wrong with AM.

[R0b0t1]

Paying special attention to power distribution tends to help, along with encasing the product in something conductive. It's also really beneficial to have some kind of test equipment in house to get a general idea, think of it like having a debugger.

The first two options are somewhat expensive, the NRE for the power supply design isn't attractive to manager types and conductive coatings for plastic or a metal enclosure are not the cheapest options. But if you're dead set on compliance it's better to frontload the design costs instead of iterating 3 times before you get to market.