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Join Date: Mar 2004
Location: Cleveland, Ohio
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It's not about gigahertz range, it's about power line related noise.
This from a recent Bill Whitlock seminar:
An Overview of Audio System Grounding & Interfacing 9/4/2012
Leakage Current Effect - A Calculated Example
• A 25-foot cable (foil shield, #26 AWG drain wire) has an end-to-end shield resistance of 1 Ω
• Measured leakage current between the ungrounded devices is 316μA (well under the UL limit of 750 μA)
• From Ohm’s law, noise voltage E = I x R = 316 μA x 1 Ω = 316 μV
• Consumer −10 dBV reference level = 316 mV
• Signal to Noise ratio = 20 x log (316 mV⁄316 μV) = 60 dB
• This is 35 dB worse than an audio CD!
• Same length of Belden #8241F cable, with its shield resistance of only 0.065 Ω, makes S⁄N 84 dB, an improvement of 24 dB!
From a noise perspective, shield resistance is the most important parameter of all.
How many times have you seen it specified on a data sheet or in advertising hype?
I rest my case about clueless manufacturers!