On 6/3/2019 1:58 PM, David Eckhardt wrote:
Really glad to see these concepts taking traction, even if they are
just limited to our small group, here.
As an EE working in pro audio, I found that I needed to join the EMC WG
of the Audio Engineering Society about 20 years ago, in self defense
from some fools in G-land who didn't understand the needs of audio
systems to pay attention from near DC to UHF. I learned a LOT from the
many fine engineers with strong backgrounds in both audio and RF -- from
companies as diverse as ABC-TV, BBC, multiple microphone companies,
equipment manufacturers, and designers of everything from recording and
broadcast studios to sound systems for churches, stadiums, theaters, and
performing arts centers. My specialty was those sound systems. I also
learned a lot of very practical EMC practices from Henry Ott in one of
his 3-day seminars c.a. 2005.
Nearly everything I recently posted I learned in those days, and I've
been preaching since getting back into ham radio about 15 years ago.
I've found most RF engineers and practitioners look down on audio
because of the very low frequencies involved, but pro audio and ham
radio have at least two VERY important parameter in common: First, the
extremely wide range of signal levels involved and the need for work
very close to noise (in audio, it's the very low level outputs of
microphones picking up quiet sources in quiet spaces), and the very wide
range of wavelengths that matter.
Audio extends over two decades of frequency, and transducers must
provide very uniform response over that range over relatively wide
vertical and horizontal angles. Transducer design, and the use of those
transducers in practical systems is several orders of magnitude more
complex than for antenna systems! We're thrilled if a high performance
antenna covers a few percent frequency range!
A lot of my teaching/preaching can be found at k9yc.com, and some of it
is in the ARRL Handbook and Antenna Book.
73, Jim K9YC
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