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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: EMC compliance question
Date: Sun, 13 Oct 2024 12:36:22 +1100
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On 13/10/2024 10:30 am, john larkin wrote:
> On Sat, 12 Oct 2024 23:30:46 +0100, John R Walliker
> <jrwalliker@gmail.com> wrote:
> 
>> On 12/10/2024 18:07, john larkin wrote:
>>> On Sat, 12 Oct 2024 12:25:27 -0400, bitrex <user@example.net> wrote:
>>>
>>>> On 10/12/2024 11:22 AM, john larkin wrote:
>>>>
>>>>> 48 is super common now. All our phones are PoE powered, which is
>>>>> typically about 54 volts. Digikey sells warts up to 65.
>>>>>
>>>>> The phones are cool. I can take one to Hawaii and plug it in and it
>>>>> works just like it does here.
>>>>>
>>>>> I imagine that europe has tens, maybe hundreds of millions of PoE
>>>>> devices with the chinese version of the CE mark molded into the case.
>>>>>
>>>>> So if european manufacturers realy have to do all the CE certs and
>>>>> testing, they have one more reason that they can't compete with
>>>>> imports.
>>>>>
>>>>
>>>> So as of 2019 it looks like the US rules are similar to the European
>>>> "can't enforce" rules in that the manufacturer takes responsibility for
>>>> everything and it's up to the mfgr how and what tests they perform to
>>>> determine compliance:
>>>>
>>>> <https://www.electronicdesign.com/technologies/test-measurement/article/21209868/recent-developments-in-emc-legislation>
>>>>
>>>> This makes it sound like it's not too expensive to do some basic
>>>> compliance tests on a small-volume product in house:
>>>>
>>>> <https://incompliancemag.com/emc-bench-notes-how-to-use-spectrum-analyzers-for-emc/>
>>>>
>>>> Need a 1 GHz-ish spectrum analyzer at least as the main tool which
>>>> aren't exorbitantly expensive nowadays.
>>>
>>> I can buy a spectrum analyzer and a surfboard antenna for under $1000,
>>> and can take a product out in the country and do an open-field test
>>> and crudely ballpark its EMI signature.
>>>
>>> CE requires screen room testing and more quantitative measurement.
>>>
>>> The reality today is that few products are honestly certified for EMI
>>> or safety, and life goes on pretty well. If a product causes massive
>>> EMI problems or hurts people, civil and criminal liabilities apply.
>>
>> My experience differs.  Every product that I have been involved
>> with has been independently tested by Intertek or a test lab of
>> similar status.
>>   > It's impressive how few EMI problems there are in real life.
>>>
>> Maybe that is because many products are actually tested and compliant.
>> I can remember when audio equipment was very susceptible to
>> interference from many sources.  Those days are mostly gone.
>> I have come across exceptions of course.
>>
>> John
> 
> Most audio equipment is digital now.

Most of most audio equipment is digital nowadays. The inputs aren't, and 
neither are the outputs. Domestic audio equipment usually gets it's 
input as a digital data stream - FM radio is an exception - but creating 
that input depends on analog microphones.

-- 
Bill Sloman, Sydney