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In Reply to: RE: Ground loop question. posted by Awe-d-o-file on March 05, 2015 at 10:21:57
The safety ground, while presenting a low impedance to ground for DC, probably presents a rather high impedance to RFI (a noise antenna). One solution that won't violate safety codes would be to install near your stereo a separate ground rod and connect it to your stereo with Litz wire in series with an appropriately sized capacitor. You would leave the safety ground attached. Since the new ground connection is made with a cap. you haven't violated code with a second ground bond and the high frequency crap now has a low impedance path to ground.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
Follow Ups:
"The safety ground, while presenting a low impedance to ground for DC, probably presents a rather high impedance to RFI (a noise antenna)."
What?
"One solution that won't violate safety codes would be to install near your stereo a separate ground rod and connect it to your stereo with Litz wire in series with an appropriately sized capacitor."
It will most certainly violate code code unless bonded to the safety ground, with or without a capacitor attached. Multiple ground points are good and can improve the ground but must be bonded together. I really don't think litz wire will improve anything over THHN or solid wire.
"You would leave the safety ground attached. Since the new ground connection is made with a cap....and the high frequency crap now has a low impedance path to ground."
If you mean capacitve reactance, yes it is a means to shunt noise to ground and works well but you need to educate yourself on what it is you trying to communicate. Impedance, resistance, reactance they are not interchangeable terms. To build a shunt you need to calculate the capacitive reactance in order to size the capacitor. Not just any old thing will do.
Cheers
Impedance is anything that opposes the flow of current. It has two components: resistive and reactive. Your house wiring has low impedance to DC. But I am very doubtful that is the case for high frequency RFI. Think of all those oxidized screw terminal connections, skin effect, etc.
The power company is concerned with separate DC grounds. All DC grounds must be bonded at one point. Using a capacitor that has a low AC impedance at the frequencies that need grounding does not violate that rule. No DC will pass through it. Unless a high voltage spike fries it. If that happened it would probably fry the litz wire too. Why litz wire? It has a low impedance at high RF frequencies.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
Using the round wire inductance calculator listed below 100 ft. of 1mm diameter wire has an inductance of 18.3mH @ 1mHz. At that frequency it has an impedance due to self inductance of 115K.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
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