Ian,
the question you posted is so generic that nobody can really answer it. It
does not give any clue regarding the sources and mechanisms of emission, no
results of your troubleshooting, nor does it give any insight into the product
and possible causes of the increased emission. If you provide much more
details, someone on the reflector might try to help you. Posting the results
of your homework would help others help you, and would show that you have done
it before asking for help. If you can't, then I believe you might be better
off hiring an expert to help you with the problem.
STP did not give you much reduction for some or all of the following reasons:
1) The shield is crimped to the shell of the Ethernet plug with only one wire
(that's standard), and then the shell makes contact with the shell of the
receptacle only with two tabs on its sides. This is far from a good RF 360 deg
contact required for good performance of a shield.
2) The location where the shell/shield makes contact with the product is at a
considerable RF ("ground-noise", i.e. common-mode) potential, so it is driving
the shield
3) The shield of the UTP is not really good to start with
Regards, Neven
-------------- Original message --------------
Dear colleagues;
Can anyone advise me how to reduce the radiated emissions from a 100 base-T
Ethernet port with a UTP cable connected to below the EN55022 class B limit?
At the moment I am 20dB above the limit at 33MHz. Using STP only reduces the
emissions by 6dB.
Thanks in advance;
Ian McBurney.
Allen & Heath Limited.
email: ian.mcbur...@allen-heath.com
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