In article ,
"Michael A. Terrell" wrote:

Telamon wrote:


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.


Technically, its NOT a utility, because they are not regulated by the
PUCO.

OK, then it is because it is a service coming into the house.

Thanks, but I've worked with switchers in radio design for over a
decade. The quoted article referred to a cable modem, which is bonded to
earth ground at the ground block. That means that the power supply is
also bonded, and any RF noise generated by the switcher will be radiated
by the shield, on its way to ground. The higher the frequency, the
worse the problem is.

BTW, Vicor sucks! We were using them in the Microdyne receivers,
till their quality fell through the floor. I tested a half dozen other
brands before we settled on another supplier that was low noise,
acceptable build quality, the switching frequency not near one of the
multiple IF frequencies, and that shut down properly on overload or
short circuit. One defective Vicor supply set a $20,000 radio on fire
and did over $10,000 damage.

That would be tough as the switching frequency is not that well
controlled and since they are usually PWM then harmonics would change
depending on the load presented to the supply output.

Oh, BTW, I worked on the 48 volt powered telemetry radio that's
aboard the ISS.

Well, that would make it a floating supply alright.

--
Telamon
Ventura, California