Posted by rowster_c on
URL: https://www.es-forum.com/The-Effectiveness-of-shielding-tp1545288p1545311.html

Sorry delay Eli, (busy having a weekend!) Will get
back with more detail on manufacturers mid week.

Uploaded some pics shielding into FILES.

Meshs: average quality available from non shielding
industry manufacturers serving other industries. You
want about 100 openings per inch (OPI). Stainless
steel readily available. What matters is good bonding
between all the strands. See pic average mesh. Copper
and other types available various places.

Metal meshs only give average shielding (40- 70 dB).
They are glittery, so a bit offputting to the eye.
Color them in black. My pic of box: took stainless
steel mesh, color it in with non removable texta and
smoke from a burning paper. Much better image quality.
Better image quality when mesh right at monitor, not
some inches away.

Mesh creates blurry screen image as it interacts with
pixels. Moire effect.Tilt the mesh at an angle (45 degrees)
to make it look good again. Also two layers of mesh is
better, but must tilt them to get rid of moire.

Have included picture of better quality mesh with
proper conductive blackening. You fix this across the
front of your monitor.

But this is not good enough. Does nothing. You must bond
it to a metal frame/box completely encasing the monitor
which I know you know. Here is the point. The termination
is everything (where the mesh meets the box at its edge).
This stuff leaks, so you lose all its
effectiveness around the rim where it meets the monitor's
metal shell. You must put good GASKETING or bonding of some sort
around the edge. Cheaply: fix tight with copper tape that
has conductive glue. Really better required: screw down,
conductive glues,
tapes or gaskets (sorry for the non engineers reading if
too many words here). That's where you will get your results.
Then Building Bio's and all will say well what about the longitudinal
waves so nothing counts unless its tested or you are a relieable
responder which you are.

Pic of my early box. You see I took a metal rectangular
frame screwed onto the box TIGHTLY forcing the mesh
onto the box, then mesh colored in texta. This is not
good enough. Probably only gives 30 dB shielding, never
measured it.

Better built window retrofitted ondisplayed in a while. I always meant
to replace this window (which was made to be replaced) with
a better one. More soonish. This is all built in to current
laptop however. (That box holds a laptop running off batteries).

Now shielding will give you 20- 70 dB across the spectrum.
A poorly designed inverter on the backlight will blow you
out by 60 dB in an instant. You need both shielding and
more importantly quiet power for a solution. Manufacturers
have let us down for economic and asthaetic reasons. Additionally
shielding has a 3 year life span if not well built- rust kills
it.

> > in absence of fiber optics,
> > a 'Ground loop cutter' (based on something called a ballun I
think)
> >is available to go on a vga video lead. This is a little box that
> >makes the signal cable carry less noise to the monitor from the
CPU.
>
> Do you have a link to such a device?

http://www.foresight-cctv.com/GB001.htm

it goes is made for cat 5 converters, sorry no more info now,
some mods to use with average VGA.

Shielded Device I now use:

It is a hardened laptop. Mil spec 3 pin plug takes power
from a 240 AC - 20V DC converter or built in battery which is
charged by said converter (currently dead off being renovated),
or I am told by a 24 V DC supply (truck batteries or 2 x 12V
car batteries) which steps down quietly to about 20 V into
the same 3 pin socket. I discussed
with a manufacturer about building such a quiet regulator
some years ago and they scoffed, but these are the
way to go. Your expertise appreciated. (If you have say
12 V of batteries, you can quietly step down to say
9 V by just wasting that 3 V buffer until the battery
runs down below say V and you have to recharge it, with
quiet circuitry.) I have the cable to
feed this 24 V into the laptop, just now must get a little
wiring converter to attach the other end to the batteries. Its
a sophisticated device overall of high build quality that allows
reproducible measurements to be made.

For the record, Per Segerback, the electrical engineer originally
from Ericsson Sweden last I spoke uses the following whenever:
instead of monitor, uses an 'LCD projector panel', which is an LCD
panel without a backlight that you lay over your projector. Grayscale.
Linear power supply, low power incandescent backlight. Previously LCD
separate power supplies backlight and circuitry as you. Charles
has commented on fans, can get rid of them using a few techniques.

Final comment: my response to this computer may simply be fortuitous
as new use of quieter machine, haven't hit the overdose period
yet as electrosensitives can. Or it could work, only multiple
opinions will show. This is the first night for me after
midnight since using it (writing now) so that is something
for me.

Rowst out for now.



--- In [hidden email],
"jaime_schunkewitz" <jaime_schunkewitz@...> wrote: think)
> >is available to go on a vga video lead. This is a little box that
> >makes the signal cable carry less noise to the monitor from the
CPU.