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Telamon · May 26th 07, 08:04 PM posted to rec.radio.shortwave

In article ,
"Michael A. Terrell" wrote:

Telamon wrote:

In article .com,
wrote:

I hate switch mode power supplies.
I hate wall warts.
And I really really hate switch mode wall wart power supplies.
Linear wall warts are bad enough.

Found this while looking for a better (as in active) RFI probe.
http://www.arrl.org/tis/info/cable-modems.html

The biggest problem I have with the linked article is that, if I read it
right, he connected the low side of the power supply output to the AC
earth ground. This causes the supply to have a specific relationship to
earth ground and might conflict with other equipment the supply, then
modem, then all else connected to it. If some other piece of connected
equipment did the same thing there would be a ground loop that could
cause equipment malfunction. Highly valuable smoke contained in
semiconductors could be released as a result.

The CATV coax shield is required by the NEC to be bonded to the
electrical system's earth ground.

That's because it is a utility coming into the house. If power supply
outputs are connected to earth ground you need to pay attention to all
other DC supplies connected to the system in other equipment. They no
longer "float" relative to each other but have a specific relationship
to earth ground.

--
Telamon
Ventura, California

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