Here is a somewhat long update on the RFI I tracked down to a local
manufacturing facility a few weeks ago.
Went to the facility a week ago with portable HF receiver and portable
tuned shielded loop in hand, but there was so much broadband white noise
within the facility that direction finding and/or sniffing of the signal of
interest was impossible (could not hear the signal of interest through the
local broadband white noise). We (the owner and I) tried watching the
manufacturing machines from a remote location where we could hear the
interference of interest to see if we could visually match up the
interference on/off sequence with machine motions, but we were not
successful. Therefore I decided I had to take a more technical approach.
I went back home and designed a circuit that would log the on off status of
the interference every second on my PC, and also used Audacity to
continuously record receiver audio. Both of these systems were connected
to my HF transceiver in my shack and they allowed unattended logging of the
interference.
Using the above recording systems I was able to tell the owner of the
facility today that the machine cycle time average was currently running 71
seconds, and that the machine generating the noise started back up after
the Thanksgiving weekend yesterday (Monday) afternoon at approximately
12:38 pm.
The owner then looked at his historical data logging system, and
immediately told me that my data matched up with his machine #18.
This afternoon we confirmed that his machine #18 was the culprit. The
owner was at machine #18 while I was at my house listening real time to the
interference. The machine was turned turned off and also ran some cycles
which allowed us to confirm the interference patterns at my house matched
up exactly with his #18 machine.
The machine is an injection molding machine (only 6 months old, with 3 more
of the same machines on order), and it has a servo AC motor. I am now
going to work with the owner to investigate the design, before we decide
how to proceed. One of the first things I want to see is if an input line
filter is part of the build, and to determine the manufacturer and model
number of the drive so I can look into the manual of the drive to see if
the machine builder followed the drive manufacturers recommendations for
RFI compliance.
Just FYI,
Don (wd8dsb)
On Fri, Oct 30, 2015 at 7:48 AM, Don Kirk <wd8dsb@gmail.com> wrote:
> Thought I would share my latest RFI issue that I tracked down yesterday to
> a local manufacturing facility located 0.5 miles from my QTH. Below is a
> link to a website that documents the interference, and it includes a link
> to a youtube video that has recordings of the interference from my shack as
> well as from within the office area of the manufacturing facility.
>
> I will now work with the facility manager to track down the actual source
> of the interference. Turns out that I am actually an old customer of this
> facility through my daytime job (very small world).
>
> website link http://sites.google.com/site/rfimetro/
>
> Stay tuned to find out the actual source.
>
> 73,
> Don Kirk (wd8dsb)
>
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