I endorse paragraph 2 below. We in GB are lucky that participation in
standards work in BSI is free. (But it doesn't stop us complaining about
the cost of BSI standards - a doozy I found yesterday is £200 for six
pages, of which three are the actual text.)
Standards work is to a significant extent supported by people who, for
whatever reason, have more than normal time to devote to it. Quite a
large proportion are formally retired, and for them, continued
participation is not only 'making a difference' but also essential
intellectual exercise.
Makers of AMNs and the like might address this issue by devising other
ways of attaching the boxes to the ground plane without using holes.
For example, if there is a sheet of steel under the ground plane.
magnets on the boxes would work.
Best wishes
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK
On 2019-08-10 10:37, Gert Gremmen wrote:
Drilling holes in (new) chamber is like drilling holes in your new
cars roof for an antenna. I can imagine your hesitation. However there
is (as long as the holes are not to big and correctly made) nothing
against it. If it allows you to reliably position your AMN devices
you need, a swiss cheese will be the best solution.
Regarding the standards... standards are written by guys like you and
me. Experts in the WG and national committees are not paid for their
knowledge (which actually is one of the finest on the planet !) , and
many of them will confirm that they (or their employer) actually need
to pay to transfer their expertise to IEC. Many members will lack
motivation (or are not allowed ) to really spend time in correcting,
drafting and searching for problems in standards texts. Participating
in standards work is a kind of charity, but for those who are
nominated to defend their employers interests. So small errors are
easily overlooked, and it seems that you found a few of them.
Please do not worry and find your own (defendable) solutions,
experiment and verify if measurement differences occur. There will be.
EMC testing is not an exact science and standards are should be read
as a generic guideline. No-one will notice the differences in set-up
and no-one will challenge them as their own experience will be
similar. If your are to be audited, referring to the open issues in
the standard might help.
Cable lay-out is the most difficult part of emission testing, and
small difference will make sometimes 10's of dB of differences. Where
the equipment set up and the room calibration will give you a
measurement uncertainty (MU) of about 5 dB (if all done right) the EUT
setup will easily add 15-20 dB to that.
Oh and if you are interested into a better test set-up than CISPR32
(former 22), look into the CISPR 16 series,especially the chapters om
measurement volumes.
Gert Gremmen
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