Questions about RFI from a Hytera MDR on a prison control system

[kristoffer]

I’m a network engineer and detention control system installer, but know little about Radio technology and it’s effects to surrounding equipment. I have a two touch screen PLC based access control system in a facility here that’s been having issues with the system shutting down and having files corrupted on the drive with the OS. The manufacturer of the system I imagine is doing anything he can think of to point blame elsewhere and has told me and the facility that the problem is a hytera MD786 mobile radio that they use for communications. His claim is that it’s damaging the SSD’s of the PC’S and we need to
Move the antenna over 150’ away. It’s a VHF radio, I believe it’s 134-176Mhz and a low power of 5W and a max of 45W. Networks and PLC programming I get, computer hardware and OS I can fix, but as far as radio equipment goes I have no idea if he’s lying, giving partial truth or I need to explicitly follow what he’s saying.

I know solid state equipment can be affected by EMI/RFI and that it being the station and antenna was only a few feet away where the facility installed it possibly had some affect on the computers, but does the rest of his claims have any Merritt? I had the facility order a remote antenna kit, and have an extra pc that I can install the OS and software on and can pretty much do what’s needed to make sure this isn’t an issue. I just want to know what you guys think is a safe distance or how to figure where to locate the antenna, and if any permanent electronic damage could’ve been done to the internal components of the PC’S and not just corrupted files. I will add that the actual PLC, SQL logging server, and I/O boards are not located in this room. His claim to locate it 162’ based on 3.6’ x 45w for an antenna rated less than 800mhz means I have to route it out of the control room, which would be difficult. It also seems like he didn’t have nearly enough info using the max wattage without knowing even the modelmodel number of the radio to even make that calculation and is blowing smoke to keep the fact that they are about to be in deep ****.

Sorry for the book, but any help or information you can give me would be greatly appreciated and if there’s anything else I can tell you feel free to ask. I will be at the facility today working on this.

[Rick]

Hi kristoffer, I think it is unlikely that the radio is causing direct physical damage to the solid state drives inside the computers, but it isn’t a stretch to imagine interference could corrupt data transfers to or from the drives.

Radios can cause interference to other electronic equipment, and vice-versa. Here are real world examples.

Awhile back my wife decided to re-arrange my son’s bedroom, which he also uses as his ham shack. This included moving his mobile ham radio rig and indoor antenna across the room. When he tried to transmit on 2m (VHF 136MHz-174MHz range), it would activate the smoke alarm in the hallway on the other side of the wall. Moving the rig back to its original location across the room resolved the issue.

I have a wireless printer in my office that sometimes interferes with reception and transmission on my Baofeng handheld when I get on the local 2m net in the mornings. When I sign on, I either need to turn off the printer or re-position the radio to hit the repeater without receiving too much noise.

I doubt the radio would cause any permanent damage to the hardware, but it could conceivably cause damage to data. If so, it would likely occur during transfer and not so much while it is in idle storage.

It is certainly possible that radio interference could be a factor, however as an old IT guy in a previous life, I will also surmise it is equally possible the issue could caused by one or a combination of any number of other things not related to the radio at all.

The way to tell for sure is to simply remove the radio equipment from the mix. Take it to another area on site or take it offsite altogether temporarily, and run the computers through their paces. If the issue suddenly clears up, it was likely interference from the radio. If not, it’s something else entirely.

I wouldn’t rely on his calculations to relocate the radio. Interference isn’t that precise and can even be somewhat unpredictable, but it can usually be resolved, once the cause is determined. If the radio is causing harmful interference, it may be possible to resolve it without even moving the radio. The tricky part is figuring out what is actually causing the interference. Once you do that, it is easier to fix the problem. Depending on the cause, it may even be an easy fix, such as simply powering the radio on another circuit.

I wouldn’t completely dismiss his assessment, but I wouldn’t just assume anything, either. If he’s a good tech, he will troubleshoot properly and thoroughly before he makes any diagnosis at all.

Edit: The easiest way to corroborate or dismiss his argument is to simply turn off the radio for awhile, if possible. If the issue doesn’t clear up, it’s not the radio.