Rene Lamontagne wrote:
On 03/15/2019 5:22 PM, Paul wrote:
Rene Lamontagne wrote:
On 03/15/2019 2:45 AM, Paul wrote:
Rene Lamontagne wrote:
On 03/14/2019 9:15 PM, Paul wrote:
Rene Lamontagne wrote:


Where do you buy copper mesh? :-)

Rene

There are kooky websites.

http://www.lessemf.com/personal.html

Nothing will get you, if you wear this stuff.

https://lessemf.com/images/a279-1.jpg

Even the person modeling that items, thinks so.

Paul


Holy crap Batman! do you mean people actually buy and wear this stuff?

Rene


Only to Knights-Of-The-Round_Table conventions :-)

I haven't seen any of "those people" riding the bus.

Paul

That last image with the chainmail hoodie might be more effective
against Killer bees, Of course you would also need a one inch thick
Lexan face mask. :-)


Rene

I just liked the look on the models face.
Like they weren't buying into it or something.

For killer bees, you're supposed to put more layers
of chain mail until it's thick enough. Maybe a dozen of
those would be enough.

*******

Back in school, the grad students in the physics department,
used to set up a card table and a chair inside one of these
and "do their homework". They used to claim, with
a smirk on their face, that it was "quieter in there" :-)
Several of the labs had these (looked a bit nicer than
this one). And rather than do experiments in there, the
cages were re-purposed with a card table and chair.

https://www.copper-mesh.com/images/c...raday-cage.jpg

When I left university, they were just in the process of
bringing 4'x8' steel plates into the lab area. They were
planning on building an entire room by welding the steel plates
together. I expect there would be a lineup of grad
students, wishing to "do their homework" in there. Don't
ask me what the steel plates were supposed to block.
Maybe the silver mesh underwear wasn't working or
something. And it's a lot of effort every day,
crafting a new tinfoil hat for yourself. A
room with solid steel walls is so much more
practical.

I would love to see how that room turned out,
and what "decorative touches" they added to it.
Like, a ventilation system.

Paul

And a little light. (or a big light).
Back in the 70's I worked a part time job for a TV repair shop to help
put food on the table, I was always handed the dogs that the other techs
had tried to repair and in many cases had twiddled the various
transformer cores to try and get decent colour and then passed them on
to me. Well by then they in variously needed a complete colour
alignment, end to end.
My test gear, Scope, Sweep and crystal marker generators, VTVM and
colour bar generators all sat on the bench and I would haul the chassis
and work on it there. For some reason which I couldn't resolve every
time some one passed near my equipment my scope traces would jump and
crawl all over the place making it impossible to do a proper alignment,I
tried all sorts of grounding and switching power outlets for both the
gear and the TV set to no avail.
Well it finely turned out I built a Faraday cage about 2x2x4 feet on
castors with Dexion iron and covered with copper mesh with only a small
opening for all the test leads to come through.
Well that did the job to my relief.

Rene

The flyback works a bit like a Tesla coil, in that
you can hold a fluorescent tube near the side of a
chassis, and the tube will light up. But it also implies
that an object passing though that field, might throw
off the parameters of the circuit a tiny bit.

It could have been inducing stuff into the
ground of the test leads. Making sensitive measurements
requires positioning the cabling for least pickup.
Which is one reason I concluded for some kinds of
measurements "why bother, it's only going to foul up" :-)
Some things, it's just better not to know. Which is
worse for your career ? Making measurements that
just aren't right, and the numbers are bull****.
Or not making the measurement at all ?

If you have "balanced pickups" it's different. We had
differential scope probes at work, a few thousand bucks,
which were a bit more resistant to that sort of thing.
But the average piece of lab equipment will come with the
default single-ended probes. (And doing A - B using
the buttons on the scope, won't do.) You need *deep* *deep*
pockets, to have any real fun in the lab. I really
appreciated having at least one or two good lead
sets to work with in the lab. Not just a 465 with
some single ended crap that could only measure
multi-volt high signals. The default probes are good
for lots of work. But the thousands of dollars probe
sets are necessary for some kinds of work.

The best toy to play with, was the diff amp for a 7000
series back in school. You could grab the diff input
probes, one per hand, and pick up your heart beat. As
the gain would work down to 1mV levels. And at damn close
to DC, to see your heart. I don't think it had quite
enough gain for brain waves (would need another 10x gain).
We had lots of toys for 7000s at work, but never that
particular module. So I couldn't do heart measurements
at work :-)

Paul