larrymoencurly wrote:

V W Wall wrote in message ...

The input line filter in the PS, which tom_w is making such a
fuss about, can only be effective if a proper ground is supplied.
Otherwise the conducted noise has no place to go but onto the
input power lines, which then act like a big antenna to radiate
the interference.

Is a ground needed for the input line filter to be effective even if
the filter doesn't connect to ground, as is the case with many Antecs,
including my 300W SmartPower? My Antec causes little AM radio noise,
but I've never plugged it into a 2-wire outlet.

The input line filter in the PS connects to "chassis ground", i.e. the
metal PS enclosure. This is connected to the computer case, which is
"grounded" (earthed) by the green wire in the line cord, which is, in
turn connected to the "U" shaped ground in the outlet.

The outlet ground, in a correctly wired situation, is connected to the
wiring conduit or to a ground wire if "Romax", (no conduit), is used.
At the power inlet to the building, these ground wires are connected
to the "building ground" and all the return wires, (neutrals), are
connected to the same point. Older buildings may not comply with
this requirement, which is now almost universal, at least in the US.

Wired correctly, this ground prevents the two power wires from acting
like an antenna and radiating noise fed into it by the power supply.
I have seen "3 prong" outlets where the ground was not even connected
or did not exist in the old wiring.

This is an unsafe situation as well as contributing to other problems.

Every RF interference situation is different, depending on the length
and position of the supply wiring, the shielding provided by the source
and the receiver, and maybe the position of the moon and stars! ;-)

After doing all the usual things, including providing a proper ground,
a lot of "cut and try" is usually called for. Of course, bad equipment
may produce interference which is very difficult to eliminate.

Virg Wall

--
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There shallow droughts intoxicate the brain,
And drinking largely, sobers us again. --- Alexander Pope