On 9/3/2013 4:34 PM, Roger Parsons wrote:
'In-phase' or 'out-of-phase' feeds are precise statements
No, they are vague, and poorly understood.
that have been understood by engineers of many disciplines (but apparently not
pro-audio) for a great deal more than thirty years.
Yes, but they are WRONG! Pro audio engineers incorrectly used those
words until we learned to use the right one about 30 years ago. And
yes, some old farts still refuse to learn new stuff. Minds like a steel
trap -- rusted shut. :) BTW -- the guy who led the charge to help us
understand this was Richard Heyser, whose day gig was at JPL, where he
worked on communications for the space program. Among other things, he
invented Time Delay Spectrometry. Dick died of cancer in 1986.
Pro audio is FAR more advanced than most RF engineers suspect, and FAR
more time in the woodshed learning new stuff is required to keep up than
in the world of RF. Think about it -- we think an antenna is really
great if it is behaved over a 10 % bandwidth, but sound transducers must
produce a well controlled response over a three DECADE bandwidth. In the
RF world, we need only be concerned with propagation one one frequency
at a time, but sound engineers must be aware of acoustic conditions over
nearly three decades of frequency (and there is huge variation over that
range). Sound engineers must deal with a dynamic range of 100 dB in a
quiet listening or recording environment, and attaining that sort of
signal to noise ratio requires noise rejection at least 10 dB better
than that.
You think DSP radios are advanced? We've been using DSP extensively in
pro audio for 20 years, and for systems FAR more complex than any DSP or
SDR radios I've seen or read about.
73, Jim K9YC
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