On 6/4/2019 9:18 AM, David Eckhardt wrote:
Yes, the capacitor termination keeps us high-frequency types happy and
satisfies the 'one end only' termination for the audio TSP designers.
I'm an RF type with some experience with audio from my long ago
college days.
This is NOT a matter of one method being right and another being wrong.
They are BOTH right in the situations in which they are applied, because
they solve issues with poorly designed, non-compliant legacy equipment,
and with equipment spread out over a large area, and in interconnections
between elements of systems running from different power sources. There
are many examples -- two or three mix consoles bridging the mic lines in
a performance facility, one of them being a broadcast truck parked outside.
Terminating the shield of shielded twisted pair at the input of audio
gear is far less of an issue if that input equipment is compliant.
Today, modern buildings outfitted with TP for Ethernet are so noisey
that radios, even at FM broadcast frequencies, are unusable. I have
lot's of 'war stories', but I'll spare those for the time being. In my
experience and regarding only RF up to low UHF, the RF noise becomes
common mode over roughly 10-wavelengths of TP length. It radiates
like an intentional antenna.
Yes. I've long recommended the use of WiFi for home networking for this
reason. In addition to the broadband noise at VHF and above, there are
also birdies in the HF ham bands. I've identified some on 30M, and
around 14030, 20152, the low end of 10M, and the low end of 6M. The
birdies can be attenuated by a few turns around a #31 core at each end
of the cable. Years ago, in Chicago, I had wired Ethernet in the house,
and it put out a lot of trash on 2M.
73, Jim K9YC
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