My 5ghz kit is interfering with what?
My 5ghz kit is interfering with what?
My incident over 2 9 years ago involves the federal regulator making impossible claims.
Working in the wonderful world of Wireless Internet Service Provider (WISPs), you get those calls once in a blue moon that makes you question everything.
phone rings
Me: G'day, this is slazer.
Caller: Hi, this is Fred calling from the ACMA (the Aussie version of the FCC). Can I talk to your senior radio engineer please.
Me: We don't have one, but I am the senior network engineer. I will do what I can do help.
Fred: Ok, I am at [site] and we are detecting some interference on the local council 80Mhz band and we believe your equipment is responsible.
Me: I am sorry, run that by me again.
Fred: We believe the equipment operated by your company on [site] is interfering with the local councils 80Mhz emergency push to talk system.
Me: Ooook. That sounds impossible our equipment is running at 5Ghz. How did you get to that conclusion?
Fred: Well, we have shut down all the other wireless operators on the tower but the interference is still there. In your cabinet there is what looks like an amp which takes up about the bottom 6RU. Would you be able to turn that off?
Me: We don't have an amp in our cabinet. That is our UPS in case there is a power outage.
Fred: A UPS? That explains why your equipment didn't go down when we turned off your breaker.
Me: It also kept beeping at you till you turned the power back on didn't it?
Fred: Yes. So is there a way we can turn your kit off so we can finish our tests?
Me: Not at this time of the day. We have clients actively using the service.
Fred: Ok, I will run some more tests and get back to you.
/call
I take down his number in case he calls back and let my minions know that if he calls put him directly though to me. I call our vendor rep, just to make sure I am correct.
Vendor: Hello this is (dude) from (vendor)
Me: G'day , it is slazer from (WISP). Do you have some time to chat, I just got off the phone with the ACMA.
Vendor: Oh boy, whats up?
Me: Well one of the ACMA "engineers" have said the kit we have installed is interfering with an 80Mhz push to talk system.
Vendor: That doesn't sound possible. If it were possible, we would have people all over the world complaining.
me: I know, just doing a sanity check. I will let you know if it turns out to be your stuff, which I doubt.
Vendor: No worries mate, thanks.
/call
I also call the boss and let him know what is going on. He has the same mind set as the vendor, impossible for us to interfere with an 80Mhz system.
A couple hours pass and he calls back.
Me: g'day mate, how did you go?
Fred: You have a radio pointed between 50 and 60 degrees off the tower, I think that is responsible for the problem.
I look up the radio in question and it is a 5.4Ghz radio.
Me: That can't be. It is a 5Ghz radio.
Fred: can you turn it off so see if the interference goes away?
Me: Like I said before I can't turn off any of our radios unexpectedly during the day, that particular radio goes to the school in [suburb].
Fred: Hmm, when can we turn it off to test?
Me: provided the school is OK with the outage, 2 weeks from now at 3AM.
Fred: Your shitting me?
Me: No, part of the contact we have with the school says we have to give 2 weeks notice for any planed maintenance that could impact their service.
Fred: But why 3AM?
Me: Because that is the time when it will disrupt the schools service the least.
Fred: There has to be a better time then 3AM.
Me: Not really, the schools nightly backup goes from 8PM till 2AM.
Fred: Seriously?
Me: Yes. I will call the school now and organise the outage. I will give you a call back when I have confirmed everything.
/call
I organised the outage with the customer and kept everyone in the loop.
Outage window came along and I got a call from Fred.
Fred: How far off are you?
Me: I am ready to go.
Fred: Eh? Aren't you meeting us here?
Me: No, why spend 2 hours travelling up there at night when I can do it from the comfort of my home?
Fred: OK, well lets get started.
I turn off all the radios except the the one I am using to log into the site via.
Me: They are all off except one, how is it looking?
Fred: Still seeing the interference. When you say they are off, I am still seeing the same amount of lights on your gear in the hut.
Me: I have turned off the radio unit on the outdoor unit. So at the moment all our radios bar one are not transmitting.
Fred: Which one is on?
Me: Our backhaul, if I turn it off I wont be able to turn it back on remotely. What I can do is bounce it. Have are you looking at your kit?
Fred: Yes.
I reboot the final backhaul radio.
Me: OK, you have about 2 min before it comes back online. How is it looking?
Fred: No different...... What in the world is causing this interference.
Me: No clue mate, we operate in the 5Ghz band. Seeing as you haven't found anything I am going to turn our kit back on now.
Fred: but we haven't finished testing yet.
Me: Yes we have, all our kit was off and you said there was no difference in the interference.
Fred: It must be your kit. It is the only unlicensed kit in the area. Everyone else is using licensed spectrum.
Me: ............. I would ask how you came to the conclusion of they don't use licensed spectrum so they must be the problem, but it is 3AM and I would like to go back to bed.
Fred: But we aren't done yet.
Me: Yes, we are. Good night.
/call
I turn on our equipment again and write up a report for the boss, then return to bed.
A couple days later, we received a warning notice from the ACMA about the events that transpired. Sadly, this is where my part in the story ends and the boss picks it up.
After several back and forth between the boss, our lawyers, and the ACMA rep. The warning is withdrawn and the 80Mhz kit gets moved to another tower a couple hundred meters down the road only to run into the same interference problem.
I don't know if they ever fixed the problem, it has been a few years and it doesn't bother me.
This reminds me of how much i miss /r/talesfromtechsupport . Thanks op
Yea, I am slowly moving my stories over. Hoping others will do the same.
Please! I miss these stories
I concur. /r/talesfromtechsupport was one of my few subreddits that were actually worth following. Thanks op!
I'm in awe why your frequency spectrum regulator doesn't have the capability to do radio directions finding to identify the interference source, rather than process-of-elimination of licensed and unlicensed users colocated on a tower. That just seems inefficient.
Here in the USA, although the FCC doesn't often roll their trucks for every single complaint, an ongoing issue like broad interference to a licensed user would tend to result in an agent being dispatched to investigate. And the FCC Enforcement Division is known for fines starting at $10,000 and going upward.
Another entity that also has RDF capabilities tends to be the electric utilities here, as they get a lot of complaints -- rightly or wrongly -- for HF and VHF interference from their equipment.
I work in the land mobile radio space, as an engineer, for utilities in the U.S. Mostly 400-800 MHz range, but our company has been trying to break into PLTE.
The FCC doesn't really mess around, and I've only had two "run-ins" with them, and they had their shit together. There was no, "I think this is this, or this may be that.". It was, "This exact piece of equipment is operating at this exact frequency, at this exact power, in this exact direction, and it needs to be doing exactly this ..." kind of thing.
Also, sometimes utilities can be bad at re-upping their licenses. That's never a fun time.
A 5GHz radio causing problematic interference at 80MHz would be worse-than-Baofeng-tier harmonics. The only thing I can think of is that some power source they're working with was causing the problem - tons of stories from radio amateurs about weird noises coming out of their radios that disappear when they unplug an appliance.
80hz has almost gotta be harmonics from a ground loop or something, given the rest of the story.
I'd love it to have been bird poop.
Very good writeup, OP.
I feel like if I walked into an unknown cabinet, turned a breaker off, and didn't see equipment go down I would start searching the web for part numbers of every major component to see if it was a battery backup. 6RU is not a ton of space for large objects.
More so if it started beeping at you after you flipped the breaker.