OUCH. Yeah, it does hurt sometimes. :-)
Bob R.
--- On Sat, 2/5/11, Bill Owsley <[email protected]> wrote:
From: Bill Owsley <[email protected]>
Subject: Re: EMC spectrum 'gaps'
To: "Untitled" <[email protected]>, "Ken Javor"
<[email protected]>
Date: Saturday, February 5, 2011, 9:48 PM
Don't ya just hate it when someone does the math the proves your speculation is
pure nonsense.
Attitude is Mind over Matter.
If you don't Mind, it doesn't Matter...
This email has been displayed using 100% recycled electrons and 100% pure
virgin photons.
--- On Sat, 2/5/11, Ken Javor <[email protected]> wrote:
From: Ken Javor <[email protected]>
Subject: Re: EMC spectrum 'gaps'
To: "Untitled" <[email protected]>
Date: Saturday, February 5, 2011, 9:35 PM
This:
“Given *NO* limits in some gaps, however, then it becomes possible that
a product could wreak havoc with other products that are susceptible at those
frequencies, so then the corresponding immunity tests would have to be
changed.”
is simply untrue. Unless the potential victims are radio receivers, in
which case there could be a problem. But there shouldn’t be any relaxations
where the radio spectrum is in common use.
Radiated immunity levels are at 1, 3 or 10 V/m. One cannot
unintentionally radiate at these levels. Assuming just 1 V/m, and 3 meters,
you are looking at 300 mW transmit power, and that’s assuming the radiating
mechanism has a gain of unity, which is highly unlikely. It also ignores the
5.1 dB headroom required by 80% modulation. If you include that, you’re looking
at an unintentional 1 Watt transmitter.
For conducted emissions, it’s the same thing. The 61000-4-6 limit is
1, 3, or 10 Volts open circuit from a 150 Ohm source. That is half those
potentials into 150 Ohms. Those levels are 60 dB or more over present
power-line CE requirements, and there is no way that sort of outage will happen
when you have to meet CISPR type requirements at nearby frequencies. And even
if you don’t have any conducted emission controls, for instance on a signal
cable, you won’t be able to meet radiated emission limits with common mode
signals on the order of 0.5 Volts or more on these cables. And here is no way
to have signals at such levels when you have to meet radiated emissions
requirements from 30 – 1000 MHz or higher, even if the limits look like Swiss
cheese.
In conclusion, allowing zones of no emissions control will not require
reworking immunity levels. There may be other reasons it’s not a good idea,
but you can’t base opposition on immunity concerns.
Ken Javor
Phone: (256) 650-5261
________________________________
From: Bob Richards <[email protected]>
Date: Sat, 5 Feb 2011 15:16:55 -0800 (PST)
To: <[email protected]>
Subject: Re: EMC spectrum 'gaps'
Derek,
If certain gaps in the spectrum have limits removed, then it would
stand to reason that someone might end up exploiting that fact. Even
unintentional radiators might position internal operating frequencies or
harmonics in those frequency gaps.
When I first thought about it, it made some sense. Given *NO* limits in
some gaps, however, then it becomes possible that a product could reek havoc
with other products that are susceptible at those frequencies, so then the
corresponding immunity tests would have to be changed.
It is something worth thinking about.
Bob R.
--- On Thu, 2/3/11, Derek Walton <[email protected]> wrote:
From: Derek Walton <[email protected]>
Subject: Re: EMC spectrum 'gaps'
To: [email protected], [email protected],
[email protected]
Date: Thursday, February 3, 2011, 2:40 PM
Thanks Ghery,
this is why I'm trying hard to ELIMINATE limits that serve no
purpose.
Anyone interested in contributing, feel free to contact me, off
list if you feel more comfortable.
Thanks,
Derek Walton
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