[RFI] Quiet Shack PC Systems?

[Ian White, G3SEK]

Jim Brown wrote:
>
> If I'm not mistaken, CE compliance is written around the EN55103-1 and 
>-2. The emissions standard is mandatory, however the susceptibility 
>standard is essentially voluntary, since it simply requires that the 
>manufacturer state the level of interfering signal to which the product 
>is immune. Those levels vary from 1 mV/m to 10 mV/m.
>
>That does not change the fact that by reciprocity, design techniques 
>that minimize emissions will tend to minimize susceptibility. But it 
>does NOT mean that other mechanisms that might not be involved in 
>emissions might not be degrading susceptibility.
>
That's basically correct.

In some ways, the main virtue of mandatory CE compliance is that it 
forces product designers to *think* about EMC/RFI - to recognize the 
problem and get a grip on it. When they take that first big step, a big 
improvement in performance will usually follow.

Our experience in CE-land has generally been that compliant products are 
usually pretty reasonable; and that very, very bad products are probably 
non-compliant. The very bad ones are probably junk consumer imports, 
possibly the very same models that are imported into the USA.

Unfortunately there are some loopholes in the mandatory CE tests, which 
are letting through a few problems. At present there is no requirement 
to test products in standby mode, and radiation from some SMPSes (eg in 
some wide-screen TVs) is turning out to be much worse in standby than in 
full operation. Also there is no clear mandatory requirement to test for 
radiation from mains leads plugged into the *output* of devices such as 
"power savers".

The TV problem is rather unexpected, something that the designers 
probably never thought about. On the other hand, the power saver problem 
may have been a quite deliberate move to save on components. In both 
cases, the solution is to close the loophole... but that will take time.


-- 
73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)

http://www.ifwtech.co.uk/g3sek