[Arny Krueger]

"Iain Churches" wrote in message
ti.fi
"Arny Krueger" wrote in message
...
"Eeyore" wrote
in message
Peter Wieck wrote:

A shielded mains cable *might* be useful against heavy
transients from equipment nearby,

How ?

*might* be useful against noise from switching power-
supplies, *might* be useful against local rF sources
(and if you discount this, you have never experienced
CB interference from truckers with massive (and
illegal) linear amps on their rigs). Operative word in
all cases is *might*.

It'll do nothing about the unscreened cable in the wall
so will have effectively zero impact.

This raises the question of why people are using
screened power cables at all. I suspect they are trying
to address very high frequency radiation which is also
being reduced by the inductance and capacitance over the
length of the power cable. This would explain why the
shielding could be effective, even though its attached
to possibly unshielded power wiring in the wall.

Hi Arny. I am grateful to John Woodgate of the ISCE for
the answer:
"The screen may be intended to reduce emissions *from*
the cable, rather than improving immunity. A Class D
amplifier, is very likely to interfere with AM radio
reception, yours or in adjacent houses. This happens even
if the emission standard, EN 55013, (or EN 55103-1 for a professional
product) is met, because the amplifier
is quite close to the receiver."

Can you see the correlation between John's answer and mine?

[Iain Churches]

"Arny Krueger" wrote in message
. ..

Can you see the correlation between John's answer and mine?

Apologies Arny. You have such a poor reputation in my own area
of expertise, that, for some reason. I find it difficult to accept that
you are any better in any other.

John is a man I really trust:-))

Cordially
Iain

[Iain Churches]

"Sander deWaal" wrote in message
...
Chris Hornbeck said:


Clamp-on ferrite chokes are cheap insurance too.


And not nearly as effective as real EMC measures inside the box.
Clamp-on ferrites have the disadvantage of the necessary air gap,
thereby reducing the effect.

I use shielded mains cables on all things digital to prevent radiation
*out*, not *in*.

Yes. That seems to be the way it was intended in this case.