My replies to a query about some sensitive instruments showing noise on-screen at a particular installation:
This tektronix page gives some ideas on how we can search for EMI, and the frequency bands we need to look at.
Here
is a link to a low cost device using an arduino for a SDR (software
defined radio) which can be tuned from 100 khz to 50 Mhz -
Ready-made SDRs are also available, for eg. SoftRock,
SoftRock RXTX Ensemble Transceiver Kit - $89.00 : Five Dash Inc. Your Source for SoftRock Radio Kits
Even
simpler might be, if you have a portable radio which can tune from AM
to SW bands, you could take that to test for EMI (which would be heard
as a KRRRR noise in some band, if you tune over all bands) and then
change volume as you move closer / farther from the EMI source.
To see if earthing is the culprit and not EMI, one possibility is:
Use some thick short 15 amp electric wire and connect together the working and non-working (noisy) equipments using their grounding lugs if any, or some sort of screw mounts on the metal part of their body.
Excerpts from S's reply:
the article is extremely informative and helpful.
i do not think grounding is a an issue. Engineers from ...
have come and checked the ...
installation which is
right below ....
They found that the Gradient Pipe which is
right below the ceiling is not shielded.
... if the power cable is passing through ...
there is noise Hence i think if we use a EMF shielded power
cable there might be noise reduction....
i have asked ...
to come with a Spectrum Analyzer and also EMF
shielded power cables...
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