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Which end of the power cord should the braided shield be grounded to?
Which end of the power cord should the braided shield be grounded to?
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Old 8th November 2017, 10:45 AM   #11
DF96 is offline DF96  England
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Steel conduit also acts as an antenna. The solution is filtering, not shielding.
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Old 8th November 2017, 05:36 PM   #12
Speedskater is offline Speedskater  United States
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Quote:
Originally Posted by DF96 View Post
Steel conduit also acts as an antenna. The solution is filtering, not shielding.
That's the "Pin 1 Problem" that Neil Muncy (RIP) first wrote about some 23 years ago.
It's why shields and steel conduits should only be connected to the chassis.
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Old 9th November 2017, 04:33 PM   #13
Speedskater is offline Speedskater  United States
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Jim Brown's remedy for power line interference is correctly chosen and placed ferrite chokes:

"RFI, Ferrites, and Common Mode Chokes For Hams" (skip over the Ham sections)
http://www.audiosystemsgroup.com/RFI-Ham.pdf

"Understanding How Ferrites Can Prevent and Eliminate RF Interference to Audio Systems"
http://www.audiosystemsgroup.com/SAC0305Ferrites.pdf

"New Understandings of the Use of Ferrites in the Prevention and Suppression of RF Interference to Audio Systems"
http://www.audiosystemsgroup.com/AES...itesASGWeb.pdf
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Old 9th November 2017, 04:36 PM   #14
DF96 is offline DF96  England
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Yes, filters - including ferrites - are the solution not shielded mains cables.
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Old 9th November 2017, 06:20 PM   #15
Kay Pirinha is offline Kay Pirinha  Germany
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Clearly a subject for the Snake Oil thread...

Best regards!
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Old 9th November 2017, 10:59 PM   #16
infinia is offline infinia  United States
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Remember folks the snake oil peddlers and others MUST invent a "problem" that their product will solve, so any of you proposing an application / solution to said product is aiding their marketing in this thread. In some cases they can point to a forum discussion like this one as some sort of validation because often there is zero censuses. I say show me the problem 1st before proposing solution. But audiophiles like the thought of extreme components somehow working in their favor by 6 dB ( majick and numerology ). haha

Sure if I live under a broadcast AM transmitter AND I use audiophile approved minimalistic gear I might see a problem and I have no doubt this so called shield could indeed make it worse before better. But otherwise youll have better luck investing that money in the state lotteries.
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Last edited by infinia; 9th November 2017 at 11:29 PM.
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Old 10th November 2017, 02:37 PM   #17
Kay Pirinha is offline Kay Pirinha  Germany
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Quote:
Originally Posted by Speedskater View Post

Power Supply and Control Wiring can also act as antennas. When I bought the house I owned in
Chicago, I upgraded the electrical wiring and put all of it in steel conduit (EMT). This shielded the
wiring, so that only the short power cords between equipment and the wall outlets could act as
antennas. The house I recently bought in California is wired with no conduit, using unshielded
parallel conductors. Thanks to its length, and the fact that it is not shielded, this wiring acts as an
effective receiving antenna for the RF I am transmitting, and an effective transmitting antenna for
the RF trash generated by computer equipment, power supplies for low voltage lighting fixtures,
and even battery chargers.
Well, this isn't any contradiction at all to what I've said before.

Best regards!
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Old 10th November 2017, 03:46 PM   #18
Speedskater is offline Speedskater  United States
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Quote:
Originally Posted by Kay Pirinha View Post
Well, this isn't any contradiction at all to what I've said before.
Best regards!
It's just a statement by an interference expert written 7 years ago, it's not a contradiction.
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Old 10th November 2017, 03:59 PM   #19
Kay Pirinha is offline Kay Pirinha  Germany
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So we agree upon that the claimed antenna function of the power supply line cannot be supressed by shielding of just the last few feet?

Best regards!
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Old 10th November 2017, 05:58 PM   #20
Speedskater is offline Speedskater  United States
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Quote:
Originally Posted by Kay Pirinha View Post
So we agree upon that the claimed antenna function of the power supply line cannot be supressed by shielding of just the last few feet?
Best regards!
I don't know about Mr. Brown, but I don't agree with that.
Especially because filters work best well above 100 kHz and much component power supply noise is well below 100 kHz.
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