[Hidden-tech] wireless networking in machine shops

ussailis at shaysnet.com ussailis at shaysnet.com
Fri Jul 1 19:44:11 EDT 2016


Here is a copy of an email I sent off. many times I have recommended using
an AM portable radio to find noise sources. It works as most of the sources
are very broadband, with a larger amount of noise in the AM broadcast band.

By AM portable I suggest the larger type, at least 6" wide. One costs +/-
$100. Anything less is a waste.

Although these radios always have the FM band and maybe have several
shortwave bands, the DF antenna is only connected to the AM band circuitry.

The suggestion for ethernet is a wise one. Here I have too many local WiFi
users. Getting a good signal on Sat morn, or Sunday eve can be a challenge.
So I use those ethernet jacks with a nice bright orange cable I lay on the
floor. At times, much faster than WiFi.

------

I've done some RFI noise reduction during my time as a RF/microwave/antenna
eng.

I even have a spectrum analyzer, albeit an older, lugable, model, as well
as just a few antennas.

Give me a call. I will ask at what frequencies are you getting noise: the
WiFi band only? (I suspect not). Are there many switching power supplies
around? I suppose there are no DC motors.

One good hint I can provide is to get an AM portable radio...
Not a tiny one, rather one that is around 6" wide or more. These usually
have a loopstick antenna. 

The interesting part is a lot of wideband noise sources radiate in the AM
broadcast band, and the loopstick antenna is very directive. This
directivity is a bit unusual in that there is a deep null at each end of
the antenna.

The reason to get a 6" (or more) wider radio is to have a reasonable
loopstick, and have it placed in the wide direction of the radio. Now
rotate the radio about it's vertical axis, and listen for a null for any
noise that you hear. It will null as the radio end is aimed at it. Do this
from 2 locations and triangulate. 

The part to remember is this only works on the AM broadcast band, because
almost no radios use a directional antenna in any other band. Since many,
many noise sources are strongest in that band, this approach makes a good
place to start.

You will find all sorts of stuff with this approach: microwave ovens,
toasters, coffee pots, computer screens, computers, printers, etc. Even CFL
lamps and LED light bulbs.

The sad part is all this stuff is supposed to be tested and approved by the
FCC. Their logo should be on the product somewhere, and if it is made in
China the product should have a hologram logo.  

The other interesting part is all radio equipment that radiates RF energy
must have an FCCID number on it. Than number is traceable on the FCC web
site.


Jim Ussailis
National Wireless, Inc.
413-585-8645
 

Original email:
-----------------
From: Robert Heller heller at deepsoft.com
Date: Fri,  1 Jul 2016 16:13:46 -0400 (EDT)
To: spike.mclarty at gmail.com, hidden-discuss at lists.hidden-tech.net
Subject: Re: [Hidden-tech] wireless networking in machine shops


At Fri, 1 Jul 2016 12:39:11 -0400 Spike McLarty <spike.mclarty at gmail.com>
wrote:

> 
> 
> 
> Anybody on the list who's worked with WiFi (or any other wireless digital
> networking) in a hostile environment?  By 'hostile' I just mean a factory
> or machine shop with lots of intermittent, bursty RFI from unknown
sources.
> Not, like, bad guys with jammers ;-)
> 
> I'm imagining somebody who actually understands WireShark filters and has
> used a radio-spectrum analyzer.
> 
> I work at machinemetrics.com - we do production equipment monitoring and
> analytics, and we've gotten outside our zone of expertise trying to do
WiFi
> at some customer machine shops where the WiFi part of the spectrum is
> really messy.

Question: Is *wireless* a requirement or just a convience? My understanding
of
machine tools is that they are not something that are moved -- they tend to
be
bolted to the floor (or are just so heavy they might as well be). The *easy*
solution would be to just run Cat 5e or Cat 6 cables (in armored conduit!).

Even if the machines themselves are not networked, having a RJ45 jack or
two 
handy by each machine or work area and then jacking in laptops with 
Ethernet patch cables might be a workable solution.

Big electric motors, especially DC (and AC/DC) ones, give off all sorts of
RF
'noise'. Fixed speed AC ones are not as bad, but can also be noisy.

> 
> -spike _/\_
> 
> MIME-Version: 1.0
> 
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