Re: OT question about blocking interference

Shadow wrote:
OT, but lots of radiation and etc experts here.
I'm a country (interior of Brazil) doc and use an ECG in the
local free state clinic, which avoids patients traveling 60 kilometers
or so to the nearest free hospital to get them done.
Recently, there has been a terrible amount of interference ,
making it almost impossible to do a readable ECG. So the manufacturers
took it back on the guarantee, and gave us a replacement, which also
did not work. Our original works fine at the factory.
So the problem is the locale, not the machine.
So I tried things like punching an earth straight into the
ground(no good), unplugging from the mains, and running on
batteries(no good either), and moving the patient and machine around.
And discovered that the clearer the view of the telephone companies'
retransmission tower, the worse the interference.
This tower probably transmits on wireless frequency,
cell-phone frequency, and maybe something in the way of bulk, as we
are between two major cities. It has a lot of drum shaped antennas all
around it's structure, pointing in various directions.
So I suggested that the ECG people find some way of protecting
from the radiation. Today the "solution" arrived, a nice big metal box
to put the ECG machine in. Of course it did not make any difference,
the machine is already shielded, it's the leads and the patient that
are not.
I thought of making some sort of screen to reflect the
radiation away, the same way a parabolic antenna will reflect wireless
to a dipole, but I have no idea on what material (mesh, sure, but what
size?), and it must be light, I might have to rush the machine and the
screen into another room if someone decides to have a heart attack.
Any ideas ?
TIA
PS, we noticed that the fatter the patient, the worse the
interference, does that make sense or is it a coincidence ?
Hi,
This comes to mind. You build a room which is enclosed with grounded metal plate walls and ceiling which ECG machine and patient can
use. I worked once radiation proof military computer system which was
installed inside a metal wall/ceiling surrounded room. This room was
grounded well and even door was triple metal chamber.

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