Richard, we make both. I don't relax the guard band. We might release a
few beta's if we pass but are within that noise margin range, but the work
continues to drop all signals to under the 3 db limit before I will sign the
ECO to release it to production status.
Theoretically at least I agree with you about the .1 as being a pass -
hence the Beta unit release, although these are tracked and occasionally
replaced. If I was only selling one product and didn't have to worry about
variation in parts and manufacturing I would give up the guard band requirement.
If rules and methods are put in place to address a problem and they do
what they were intended to do, regardless of some level of uncertainty then we
should quit mucking around with them and get onto other issues. If and only if
they aren't resolving the issue should they rules/ methods more stringent,
reduce the margin of uncertainty, or develop whole new methodologies.
If it isn't broke don't fix it, but we like to fuss and make things
"better" even when unnecessary just because we can, and it often costs alot of
time and money. A sledge hammer is unnecessary to kill a fly - although it
satisfies me a great deal!
And now the firestorm of e-mails start.
Gary
-----Original Message-----
From: Stone, Richard A (Richard) [mailto:rsto...@lucent.com]
Sent: Wednesday, December 19, 2001 5:06 AM
To: Gary McInturff; Doug McKean; EMC-PSTC Discussion Group
Subject: RE: EMI guard bands
Does anyone make Class A AND Class B
products?
if so, do you allow for a much smaller margin on the B
since its approx. 10 db quieter than A to start with.
or do you treat them equally.
Also Oats site to Oats site can differ as much as +/- 4 db
do to many factors.
any comments?
Richard,
-----Original Message-----
From: Gary McInturff [mailto:gary.mcintu...@worldwidepackets.com]
Sent: Tuesday, December 18, 2001 1:19 PM
To: Doug McKean; EMC-PSTC Discussion Group
Subject: RE: EMI guard bands
I hold with the 3 db under class B, as well as A. The only effective
argument, in my mind, is the uncertainty of measurement issue. Beyond that I
find that if I have 3 db everywhere my measurements next time down with that
product or with one off the shelf have also been compliant. So if pragmatic
repeated measurements is telling me I'm in then I am not going to spend the
time and money to make even more sure that I am in. The goal is to not
interfere with communications not to be invisible at all costs. If it ain't
broke I'm not fixing it.
Obviously, others disagree. By the way if a customer requests it,
they get what they want, if they want to pay for it, and I have never
rejected products with a 3 db band - and they haven't bitten me yet either.
My couple cents
Gary
-----Original Message-----
From: Doug McKean [mailto:dmck...@auspex.com]
Sent: Monday, December 17, 2001 3:15 PM
To: EMC-PSTC Discussion Group
Subject: Re: EMI guard bands
"Tania Grant" wrote:
>
> Amund,
>
> My minimum criteria and recommendation has always been at least 6dB.
> However, how many engineering managers, upon finding a 1.5 dB margin
in
> their favor, rule "ship it"!
<nod>
Although in some markets, there are customers who
require -6dB under the Class A limit. Although if I had
it my way, I'd make it about -10dB under the limit.
- Doug McKean
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