Re: comment 3: "... This process maintains the INTENT of the
emissions spec in the first place - that is to maintain a KNOWN level of
interference." That is not the itent. The intent is to protect radio
reception betwen 30 - 1000 MHz(now extended to 6500 MHz). Knowing that
the level is 20 dB higher than that required to protect radio rception
is not terribly useful.
> -----Original Message-----
> From: Grasso, Charles (Chaz) [SMTP:[email protected]]
> Sent: Friday, June 18, 1999 6:05 PM
> To: 'Morse, Earl'; 'Lou Gnecco'; [email protected]
> Subject: RE: NEAR/ FAR FIELD CORRELATION ISSUES
>
>
> Actually Earl - I am in complete agreement with you. I think you
> may have misunderstood my comments. Let me explain:
>
> 1. On the CE+CE maybe = CE comment. No question here. I agree.
> Many systems fail emissions (maybe immunity) testing due to
> incompatible combinations. BUT... As I am sure you know, the
> FCC has a Class B compliance system that allows for exactly that.
> PCs can be
> assembled from sutiably marked components (such as video cards)
> and marketed WITHOUT furthur testing. This results in non-compliant
> units (admitted by the FCC) released on the market place with
> NO intent by the FCC to enforce the rules.
>
> (BTW - The Australians have released an equivalent scheme
> with the proviso that a metal enclosure be used)
>
> 2. Here is the crux of my issue with the FCC. The logic and the
> physics don't match. To illustrate: A recent thread has described
> the origin of the emissions standards and generally everyone
> agrees what a jolly good thing it is too. That being the case,
> how could the the FCC put into law a process that allows for
> systems to be released on the market place WITHOUT testing.
> To me the existing FCC Class B procedures render the emissions
> standard irrelevant. After all why should any manufacturer concern
> themselves with the standard when the FCC blatenly ignore it
> themselves?
>
> 3. If you have monitored this list recently, you should
> have seen my comments regarding the emissions limits.
> To reiterate: Raise the limits 20db but make EVERYONE
> test. Although this may seem ridiculous - compared to the
> FCC Class B process it makes a lot of sense. This process
> maintains the INTENT of the emissions spec in the first place
> - that is to maintain a KNOWN level of interference.
>
> OK -OK so folks will bleat about cycle time etc...
> So an alternate solution is to truely engineer the EMC at the
> component level. Design tests/procedures to adequately test
> at the componet level AND (this is key) have the regulatory
> agencies redesign the emissions limits to meet the 21st Century.
>
> Call me if you want to chat furthur.
>
> -----Original Message-----
> From: Morse, Earl [mailto:[email protected]]
> Sent: Friday, June 18, 1999 3:36 PM
> To: Grasso, Charles (Chaz); 'Lou Gnecco'; [email protected]
> Subject: RE: NEAR/ FAR FIELD CORRELATION ISSUES
>
>
> I beg to differ.
>
> It is ludicrous to believe that components or for that matter
> subassemblies
> can be certified and then combined to make a compliant system.
>
> CE + CE doesn't always equal CE
>
> The reduction of emissions is highly reliant on component placement.
> The
> same parts can be arranged on circuit boards in compliant and
> non-compliant
> patterns. Same with subassemblies.
>
> While the current measurement techniques are difficult they are about
> as
> close to the "truth" as we can get. Even if that means an 8 dB swing
> from
> site to site.
>
> The reason that we see PCs consistently fail by as much as 20 dB is
> because
> of a lack of enforcement. Many computer manufacturers sneak through
> the
> requirements with their one of a kind golden units never to worry
> about
> compliance again. Very few get caught and it is worth the bucks to
> keep the
> production lines going rather than shutdown the lines.
>
> Who was the last computer manufacturer you heard of that was forced to
> shutdown until an EMC problem was fixed? I have a book of test
> reports on
> competitor's products. They fall into the categories of compliant,
> near
> compliant (looks like they tried), and fails miserably (didn't try,
> didn't
> care, and outright lied on any self declarations). The failing
> companies
> seem to be doing just as brisk a business as the passing companies
> without
> having to worry about the cost of EMC.
>
>
> Earl Morse
> Portable Division EMC Design
> Compaq Computer Corporation
> Phone: 281.927.3607
> Pager: 713.717.0824
> Fax: 281.927.3654
> Email: [email protected] <mailto:[email protected]>
>
>
> -----Original Message-----
> From: Grasso, Charles (Chaz)
> [mailto:[email protected]]
> Sent: Friday, June 18, 1999 10:33 AM
> To: 'Lou Gnecco'; [email protected]
> Subject: RE: NEAR/ FAR FIELD CORRELATION ISSUES
>
>
> I cannot agree more!! We, not the government, need to
> drive the technology for EMC.
>
> I have followed this thread with interest. I have long
> believed
> that if EMC was to maintain credibility we (EMC ) would
> have
> to
> come up with a method of demonstrating compliance in
> spite
> of the
> many and varied combinations. One way is to test at the
> component
> level - like our Safety brethren - and call the assembly
> of
> tested
> components good!!
>
> This is methodology can be made consistent with good
> engineering
> design practice unlike the existing FCC rules for Class
> B
> equipment.
> On the surface the FCC Rules appear to be similar to
> component level
> testing - but under the hood, they are completely
> different.
> There are
> PCs out there that fail by as much as 20dB.
>
> I am all for a more logical and consistent design
> approach
> to EMC!!
>
> Thank you
> Charles Grasso
> Advisory Engineer
> StorageTek
> 2270Sth 88th Street
> Louisville CO 80027 M/S 4247.
> Tel:303-673-2908
> Fax:303-661-7115
> email:[email protected]
> Web Site:
> http://www.ewh.ieee.org/r5/denver/rockymountainemc/
>
>
>
>
> -----Original Message-----
> From: Lou Gnecco [mailto:[email protected]]
> Sent: Friday, June 18, 1999 6:52 AM
> To: [email protected]
> Subject: Re: NEAR/ FAR FIELD CORRELATION ISSUES
>
>
>
> For this to work, the government would have to change
> the
> rules completely,
> setting a new set of near field procedures and limits.
> This
> is doable but
> hard to sell.
>
> A good way to start would be if we did it. If
> someone in industry
> writes up a procedure and a set of limits, then everyone
> could use that as a
> "straw man", (criticizing and refining it) until
> eventually
> most people
> agreed.
> Eventually it could become an industrial (such
> as
> IEEE) standard.
> Then the govt would find it much easier to adopt it as
> is or
> after making
> their own modifications.
>
> lou
>
>
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