On 11.05.15 23:14, Tom Easterday wrote:
> I will do that tomorrow.  I wonder if using this tape to shield
> unshielded wire, like my VFD to motor cable, would work….?
> http://www.cesco.com/b2c/product/9770?utm_source=google&utm_medium=cpc&utm_campaign=shopping&scid=scplp2640202&gclid=CMTdkaSbu8UCFZeDaQodlRgAHQ

That or copper tape can be used for shielding, but still forms a coiled
inductor back to the cable ends, unless contact between turns is very
good. Can you run two tape lengths longitudinally, overlapping their
edges around the cable diameter, and stitching them into a
tube with frequent solder joints? Minimum impedance, at RF, back to your
star earth (from one end only) has to be good, after shutting it in.

Or, do you have some Al or Cu tubing in the junkbox, that you can bend
after pushing the cable through? If it's to hand, it's something you can
do without waiting for deliveries, and should work at least as well.
If it's primarily magnetic coupling, then steel tubing might be better.
Experimenting with a (mostly) closed steel box around the computer can
help determine that.

The power radiated is proportional to the open area between the two
power conductors. If they are twisted, e.g. one turn per inch, then that
is minimised, and there is less work for shielding to do.

My mini-ITX mobo is powered by a picoPSU, so can run off a 12v battery.
Thus isolating power entirely, and disconnecting the parport or other I/O
would allow checking whether Axis still plays up - proving that it is
radiated EMI. That may be hard to do there.

It'll be very interesting to hear what finally cures it.

Erik

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