It is with great sadness that I acknowledge the passing of an modern
engineering giant. Neil Muncy was elected a Fellow of the Audio
Engineering Society for what has turned out to be the most important
work on RFI during my lifetime. His landmark paper, which I heard him
present at an AES Convention in November1994, and which was published in
the Journal of the AES in June, 1995, exposed two fundamental mechanisms
by which RFI is coupled to audio systems. Reprints of that JAES issue,
which also included important work by Bill Whitlock, are the largest
selling ever.
The first of those mechanisms, which, at the suggestion of AES
colleague(and the founder of Neutrik)Bernhard Weingartner,. he called
"The Pin One Problem," is the primary cause of RFI in virtually ALL
modern equipment -- audio, computers, video, even ham gear. The Pin One
Problem is simply the mis-termination of the cable shield -- rather than
the proper connection to the shielding enclosure, the shield is
improperly connected to circuit common, where it wanders around the
circuit board and eventually finds the shielding enclosure. In that
wandering, shield current produces IZ drops that are injected into
active signal circuitry at the whim of the circuit layout artist, RF is
detected and amplified. As Neil so poetically put it, "the fox is in
the henhouse." As it turns out, by reciprocity, the Pin One Problem is
also the primary cause of RF noise emitted by badly designed equipment.
The second mechanism he exposed was the imbalance in the inductive
coupling between the shielded twisted pairs and the drain wire of
foil/drain shielded cable. The imbalance caused a conversion of common
mode current on the shield to a differential mode signal on the pair.
The imbalance was the result of the fact that the drain wire was twisted
at the same rate as the signal pair, and was closer longitudinally to
one conductor than the other. The type of cable he was addressing is
used in 99.99% of all audio equipment racks, and in nearly all
permanently installed audio wiring outside of equipment racks. .
As it happens, it was Neil Muncy who first taught me about variable
speed motor control systems and the noise they produce. I was Vice Chair
and he was a founding member of the Working Group on EMC of the
Standards Committee of the Audio Engineering Society, and In a long
visit to his suburban Toronto home around 2004 he showed me and a
colleague who was the Chair of the Working Group an engineering report
by a manufacturer of those systems detailing the RFI issues their
systems were causing their own equipment!
Neil Muncy didn't work only on EMC issues -- like me, as a ham working
in pro audio, he understood RFI, and stepped in to learn about and
address the issues he encountered as part of his work on systems he was
designing, as well as those he was troubleshooting for others. Neil
mostly worked in electroacoustic design -- systems for sound
reinforcement and for control rooms in recording and broadcast studios
-- and he also worked in the area of audio signal processing for
broadcast and CATV systems. Neil was also the EMC troubleshooter of
last resort. I worked with him on two projects, both of which taught me
about the noise issues associated with high-leg Delta power distribution.
Most important, Neil was a great teacher -- in the grand tradition of
ham radio, he truly believed in "passing it on" to others. Neil wasn't
an active ham -- his license had lapsed many years ago, but the attitude
remained. I've spent countless hours around a kitchen table, in bars,
in the hallways at conventions, and in formal tutorial workshops that he
presented at AES conventions and trade shows. Much of AES48, AES54-1,
and AES54-2 were first drafted by Neil and me at my kitchen table, and
later worked over (a lot) and adopted by the Standards Committee Working
Group.
My favorite Neil Muncy-ism is his response to a question in a tutorial
workshop about the importance of an earth connection to solve RFI
issues. Neil responded, "Grab a couple of six packs of your favorite
brew and a comfortable chair, park yourself at the end of a runway at
O'Hare (this class was in Chicago) with a good pair of binoculars to
watch those big jets taking off, and CALL ME COLLECT when you see one
trailing a ground wire."
Neil's methods of research and publications have been a model for my
own. As he told me one day, "I published what I did and exactly how I
did it, my results, and my analysis. You're welcome to repeat my work
and verify it, and to question my analysis." When I repeated parts of
his work using very different methods, my results correlated well with his.
Neil Muncy was a guy who made a difference -- by his thoughtful
analysis, by the research he published, by his teaching, and by
eventually changing an industry. In 1994 when he presented his paper,
virtually ALL audio gear had Pin One Problems. In the years before his
death, Pin One Problems were almost unknown in the pro audio world,
although they still abound everywhere else. If one of my chokes kills
the RFI, it's almost always fixing a Pin One Problem.
Neil Muncy was a hellava guy. RIP, Neil. And thanks for EVERYTHING.
73, Jim Brown K9YC
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