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Walkie Talkie Interference
Keying microphone(s) causes computer LCD monitor to black out.

I was informed recently that whenever one of the operators keys a microphone on his radio that the camera monitors in the operating pulpit blacks out. We have three monitors that display various locations of one of our operations. Monitors are labeled "A","B","C", from left to right. All the ethernet, HDMI, and electrical connections are tight. The problem only occurs on one monitor unless I turn it off. Then it moves to the next one, and it doesn't happen to any monitors not connected to the camera server. The server itself resides downstairs so there is a concrete slab floor between it and the operating pulpit. Any ideas what I need to fix this problem?

By Jeremy Pollard on 5 December, 2016 - 6:26 pm
2 out of 2 members thought this post was helpful...

Wow.. is this a MENSA question?? Well I have to ask... if another user below the concrete slab had a radio could you talk to them?

My angle on this that the frequency of the RF is interfering with the video card. if you have 3 monitors, and only the first one (A) goes dark but the other 2 stay on, AND when you turn off the first one then the 2nd one would go dark, the video cards of today know when a monitor is connected and powered.

So it seems that the issue may be with the video card, and for some reason takes only one of the 3 connected and powered monitors... if the RF was interfering with the monitors and/or their power supplies, then all 3 would go true?

There was an instance with power supplies at a pulp mill way back.. with the panel door open and a walkie was keyed, the p/supply would groan. And the panel would shut down.

Keep us in the loop :)

Cheers from: Jeremy Pollard, CET The Caring Canuckian!
Crisis, necessity, change

Any resolution to this? I'm having the exact same problem.

>I was informed recently that whenever one of the operators
>keys a microphone on his radio that the camera monitors in
>the operating pulpit blacks out. We have three monitors that
>display various locations of one of our operations. Monitors
>are labeled "A","B","C", from left to right. All the
>ethernet, HDMI, and electrical connections are tight. The
>problem only occurs on one monitor unless I turn it off.
>Then it moves to the next one, and it doesn't happen to any
>monitors not connected to the camera server. The server
>itself resides downstairs so there is a concrete slab floor
>between it and the operating pulpit. Any ideas what I need
>to fix this problem?

1 out of 1 members thought this post was helpful...

it can be a real problem, typically it requires the transmitting antenna to be in close proximity (centimeters. But if the handheld is linked to a higher power system used for plant wide coverage, in some of the larger plants, it could be a larger problem.

Typically in such cases you get toroid ferrite or clamped cores, placed at the various cable junctions, but the very first step should be too check the wiring shields and make sure they a properly grounded.

Plant grounding is always a problem in operating plants.

The cabling is set up as such.

The HDMI cables come from a designated computer with 3 HDMI ports. The three HDMI cables plug into adapters that convert them into Cat5 cables which go from one of the operator pulpits up to the ceiling. Then they get converted back to HDMI and plug into their respective monitors. The only place I can imagine that they would be grounded is in the computer and the monitors, so they are probably acting as antennae because the cat 5 cables are neither grounded or shielded.

Regards

2 out of 2 members thought this post was helpful...

best to use metallic conduit or cable tray grounded to your computer or instrument ground system.

By W.L. Mostia on 18 July, 2018 - 1:46 pm

Any signal wiring that does not have protection against EMI can potentially be sensitive to radiated walkie-talkie transmissions. Such protection can potentially include grounded metallic conduit or raceway as already mentioned, metal enclosures, separation, shielded cable, ferrite bead or cores, twisted cable, etc.

William (Bill) L. Mostia, Jr. PE
ISA Fellow
Principle Engineer
WLM Engineering Co.

Thank you Bill.

How can cables be shielded that are currently not shielded? We have a security center that has a bank of security monitors that all go black if the person observing the bank uses his or her radio, which poses an obvious momentary risk. Can the cables lying all over the floor be enclosed in something that would help the situation more in one material than another?

Thanks in advance.
Rob M

1 out of 1 members thought this post was helpful...

Rob M,

Since I do not know how your cables are run, their sizes, or the relationship to the walkie-talkies, I will have to guess at what will help you. To fixing problems like this, one really need to see what the physical arrangement is and see the problem in action, and then it sometimes it still boils down to experimenting.

For individual cables, the braided shield may help. For the walkie-talkie frequency, grounding the cable at both ends would be appropriate. I would also put a protective sheath around the braid too.

https://www.cableorganizer.com/metal-braided-sleeving/

The web page says it provides protection from 0.5 mHz to 1.7 mHz but its data sheet (see Click for More Features https://www.cableorganizer.com/metal-braided-sleeving/#features) says "Provides superior attenuation of greater than 60 dB over wide frequencies, ranging from a few kilohertz (kHz) to several gigahertz (gHz)." This should be enough if the walkie-talkies are not too close.

Search Amazon for "emi shielding sleeve"

Here is some shielding mesh:

https://zippertubing.com/materials/shielding/mesh-shielding/shx-4-ss

Here is some shielding tapes.

https://www.knitted-mesh.com/products/knitted-wire-mesh-shielding.html

I would talk to the engineers at these websites to see if they can help you. You may have to experiment some to see what works. Most of this stuff is not too expensive.

There are some enclosed metal wireways:

http://www.delikon.com/automat1.htm

Let me know what happens.

Regards,

Bill

William (Bill) L. Mostia, Jr. PE
ISA Fellow
Winner of the 2017 ISA Raymond D. Molloy Award
Sr. Functional Safety Consultant
SIS SILverstone, LLC, http://sissilverstone.com