On 12/25/2022 1:14 PM, Hare, Ed, W1RFI wrote:
My test fixture was a simple ceramic socket, placed in a C63.4 compliant room. I then
purchased on of the "cans" that most spotlight bulbs are installed in, and
grounded it to the room ground plane. The conducted emissions increased by 8 dB simply
by using the bulb in a way that it is very likely to be used. To me, this speaks loudly
to the need to make revisions to the test standards, which simply measure the bulb pretty
much the way I did.
YES! Almost 20 years ago, UK members of the AES Standards WG on EMC
observed that proposed regulations there would include interconnections
somewhat representative of a product's use in a system.
My real world experience with EMC in my premises is that most noise is
radiated and most susceptibility occurs as common mode coupling to/from
wiring connected to the source/victim, which acts as an antenna. That's
why multi-turn ferrite chokes work.
For the ordinary ham, a VHF/UHF talkie with wide-band receive makes an
excellent probe around sources and their wiring. A year or so ago, I
added a Starlink system, powered from an outlet just outside my shack,
with the dish on the roof of the outbuilding that houses the shack.
Probing with the talkie found it to be a strong noise generator, so I
added multiple clamp-ons to both the AC cable and the 75 ft cable to the
dish. Had I checked for noise before the dish was mounted to the steel
roof, I would have added one or more chokes there, but metal roofs are
slippery, and it's not easy to find people who can safely work on them.
The talkie detected significantly less field as it was moved past the
chokes both to that cable and to the AC line. A 160M Tee vertical
(that's always been relatively noisy) is my only antenna that's close to
the shack, about 25 ft from the Starlink PSU; other nearby antennas are
coax-fed at least 120 ft in the air, and choked at their feedpoint.
73, Jim K9YC
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