Interesting indeed -- I first proposed a concentric capacitance in the
course of an AES EMC WG meeting as a solution to the need to break the
shield at one end of a cable to prevent excitation of legacy Pin One
Problems. I was thinking "feed-thru" for the shield. Joanne Dow, a WG
member based around LAX, suggested the addition of the bead. This was in
the late '90s, and I knew nothing of ferrite then! It was John Woodgate,
from the UK, who proposed the circumferential array of SMT caps, and who
subsequently ran extensive tests of an engineering sample. Engineering
people from Neutrik had long been active in the WG.
Another critical piece of this series of Standards came from Bill
Whitlock, whose work on the Balanced Interface showed that if the cable
shield is interrupted, that the interruption must be on the receiving
end. This was counterintuitive to some of us, including me, but Bill
changed our brand of booze. In addition to being Chief Engineer of
Jensen Transformers, the world's best, and having done extensive design
work at major LA recording studios, Bill has had serious RF consulting
projects in the UHF range. :)
The resulting product was a quite effective band-aid for VHF and UHF in
legacy equipment with Pin One Problems. Most (but not all) of the WG
members who made the most important contributions to AES EMC Standards
were hams.
I was (and still am) Vice-Chair of the EMC WG, and chaired the writing
group that developed that series of Standards.
Also critical to our final product was understanding the difference
between shielding and grounding. We connect the shield to the shielding
enclosure NOT to "ground" it, but to make the shielding continuous! It
was the late Ray Rayburn (a ham) who came up with the phrase "shielding
enclosure" to solve some arguments with the "physics-challenged."
I learned a LOT from the serious brain-power during my work on AES
Standards. It was like free grad school!
73, Jim K9YC
On 4/23/2023 4:07 PM, Paul Christensen wrote:
The discussion in the link above concludes with a reference to the Neutrik
EMC series XLR connector. It uses an integrated capacitor between Pin 1 and
the shell. For anyone not yet bored by the discussion, have a look at the
bottom table, "Pin 1 Problem" in this Neutrik application note where the EMC
capacitors are shown:
https://www.neutrik.com/media/9117/download/typlical-application-emc-xlr.pdf
?v=1
I'm a bit skeptical of the effectiveness across a broad range of EMI/RFI but
it looks like it may be an "AES acceptable" way to join two midpoint XLR
connectors. The top of the application points to my original concern. See
"Interrupt of Circumferential Shield," and "Connector Shell Floating."
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|