Power line interference and digital radio

[vsp5151]

I have experience with power lines interfering with low, high and UHF two way radio receivers as a power company telecommunications person and as the person who had to look for interference but I am wondering if anyone has had interference to their digital two way radios, especially P25. I just got a P25 XTS3000 and have an amateur P25 repeater and several state police P25 receive only channels programmed and am starting to look for interference issues to document them. My thought is that digital radios will be degraded by power line noise but the users may not know the radios are degraded and will never know what is causing it. Any thoughts?

 

[johnls7424]

Power lines cause RF interference all the time. There is nothing sadly you can do about it if the power lines per se were there before you either moved to the area or were licensed for a certain channel to use. What the FCC I have seen do is allow a user who is licensed ( usually for public safety purposes) allow them to use more WATTS for output to counteract the degradation of the radio system due to this phenomenon. Sometimes at a certain amount of power ERP can be justified to counteract the interference. They WILL NOT take down a power line grid because you have interference from it. They can work with you to help ease your suffering from any electromagnetic pulses from lines or static electricity in the air causing your interference by allowing exceptions to be made like I stated above to help you.

 

[johnls7424]

I have experience with power lines interfering with low, high and UHF two way radio receivers as a power company telecommunications person and as the person who had to look for interference but I am wondering if anyone has had interference to their digital two way radios, especially P25. I just got a P25 XTS3000 and have an amateur P25 repeater and several state police P25 receive only channels programmed and am starting to look for interference issues to document them. My thought is that digital radios will be degraded by power line noise but the users may not know the radios are degraded and will never know what is causing it. Any thoughts?

Analog radios would be more affected to power lines then digital. Even though in a sense both can be effected equally the analogs receiver end would notice the static more though. Digital radios have noise canceling out technology ( modern ones at least do with AMBE Vocoders) to help combat static from power lines.

 

[12dbsinad]

For us power line noise usually doesn't affect us all that much unless there is something drastically wrong. Normally you will hear more complaints on lower frequencies, especially HF. Also, it doesn't matter how the audio is modulated (P25, NXDN, DMR, analog, etc) interference affects the frequency range so everyone is affected.

We have more issues with EMI generated from cheap switching power supplies, lighting fixtures, electronics, vehicle computer systems, and even your cheap 12V cellphone charger. It affects our in-building coverage drastically because of this. Something you can't predict and computer RF maps don't show.

Even the new heat pump control boards at out fire station generated enough stray RF junk that you could easily pick it up from way outside the building. Each board generated this, times that by 8 or 10 for that many control boards and you have a mess. Luckily, the companies engineering Dept fixed this and replaced them all for us.

 

[mmckenna]

I've got a trunked NexEdge 800MHz system I manage. I've got users who work on our high voltage distribution system (12KV), a 4.2MW turbine plant and a hundred or so smaller standby generator systems. I've never heard any complaints from any of our high voltage crews or any of the guys working around the other stuff, including transformers, switch yard, etc.
Doesn't mean it isn't there, but they are not complaining. Never had any complaints on our analog trunked system either.

 

[MTS2000des]

We have more issues with EMI generated from cheap switching power supplies, lighting fixtures, electronics, vehicle computer systems, and even your cheap 12V cellphone charger. It affects our in-building coverage drastically because of this. Something you can't predict and computer RF maps don't show.

Even the new heat pump control boards at out fire station generated enough stray RF junk that you could easily pick it up from way outside the building. Each board generated this, times that by 8 or 10 for that many control boards and you have a mess. Luckily, the companies engineering Dept fixed this and replaced them all for us.

Yup. What he said.

FWIW, utility companies are usually VERY responsive to legitimate complaints from licensed spectrum users. At the end of the day, they are losing electricity which means losing revenue.

The cheap crap from China sewage electronic factories could care less. And since the FCC leaves all the burden on the licensee, don't expect this problem to go away.

Radio spectrum enforcement is pretty much on our own shoulders. The FCC OET will rubber stamp anything sent in from a testing lab (so long as the check is good), and part 15 devices are pretty much a free for all.

Pollution on our radio spectrum is well on it's way to being a huge cloud of smog.

 

[SCPD]

I'm gonna kinda veer this conversation off a bit, but I'd like some thoughts on this:

What if someone was to build some sort of low pass filter that took everything above, let's say 1 KHz to ground, and plugged it into a wall outlet, or put it across the incoming.

You think that would attenuate high frequencies from power lines in the neighborhood? I don't know the answer, but the thought crosses my mind from time to time as to how well that may (or may not) work.

 

[NDRADIONUT]

ZZZZZZZAPED.....

 

[buddrousa]

What you are looking for is a loose crimp, clamp ect at a splice, transformer, weather head, tap. We had noise and it was found by our electric company

 

[wb6uqa]

If you hear noise on UHF you are very close to the source. Noise is AM modulated.

 

[rfradioconsult]

A hand held scanner is a good way to track power line interference, tune to about 135 MHz in am mode. Electrical utilities are very responsive to RFI complaints, they do not want to get a letter from the FCC, which happens frequently. The will come out with an array of equipment including a parabolic receiver to listen for a leakage path (arc) or hardware problems. When I worked for an electrical utility the RFI was handled by our Telecom techs, they had quite an array of equipment including a TS440 mounted in their van. After I retired they went through the bad move of putting Telecom under IT, the RFI guy now is part of the substation maintenance group.

 

[vsp5151]

Wyandotte and RF Consultant

Wyandotte, good idea but most of the RFI is radiated through the air into the antenna and receiver. I worked RFI for 15 years and never had a case of conducted interference through the secondary power line. RFConsultant you are right on about telecommunications being absorbed by the IT department and RFI duties being passed onto a group that does not understand radio. Usually it doesn't work well.

 

[prcguy]

I've dealt with an amount of power line zap problems and although it can extend up past 200MHz it rarely causes the same complaints as it does on HF. However, I had a major problem at VHF in my house that killed all but the strongest repeaters heard on handhelds inside my house.

Turns out I had just replaced all the lights in my house with Cree brand screw in LEDs from Home Depot. I found with the lights off all my 2m amateur and 150MHz P25 Govt radios worked as normal, but turning the lights on caused all radios actively receiving to squelch. The moderate to weak stations and repeaters just disappeared, including the Govt P25 system and the really strong analog repeaters had a continuous hiss in the background and if I moved the handhelds much the strong stations would go from weak hissing to completely gone and the radio was squelched.

The HF spectrum did not seem to be affected and I didn't detect any problem at UHF, so these lights were puking a bunch of RF mostly in the VHF spectrum. Unfortunately my spectrum analyzer is broken and I couldn't characterize the noise as precise as I would have liked.

I was not happy as it cost a small fortune to outfit the whole house with new LEDs, so I experimented on a group of the most offending lights closest to where I use handheld radios in the house. I unscrewed all but one light (ceiling can type), pulled the fixture apart and started adding type 43 snap on ferrite beads. Unfortunately there was not enough slack in the wires to get multiple turns through the bead but one bead made an improvement, two was better and three quieted things down to where it was hard to tell if the light was on or off. Three beads was also the maximum I could fit on the available wire in the can fixture.

I then found a great deal on a similar type of snap on bead, I think it was 70 for $20 plus shipping, and I reworked all the can lights in the house. Now with about 25lbs of ferrite in the ceiling I can use my handhelds anywhere in the house on VHF again and life goes on.

When I get my spectrum analyzer repaired I'll probably take off some ferrites, take pictures of the interference and have a conversation with Cree on refunding some $$ and maybe follow up with a complaint to the FCC. I imagine these lights are in use somewhere like a police station or hospital where communications are being disrupted and they don't know why.
prcguy

 

[vsp5151]

Your comment on the govt P25 systems disappearing is exactly what I have suspected. P25 uses FM and power line noise should affect the P25 radios similar to what it does to fm two way radios typically low and high band however the error correction in the radio may correct some of the degradation. I have a Home Depot LED screw in replacement bulb im a lamp and when I listen to the weather 162.55 and turn on the LED lamp, the weather channel disappears. I want to try a similar test with some weak P25 state police receive only channels. Thanks for that information.

 

[speedway_navigator]

My experience with power companies and RFI is similar to rfradioconsult and no where near johnls7424.

The local power company in northwest IL lent us a detector when we were working with a noise problem for the sheriff and fire departments.

See DA 13-2077 for the FCC's response to RFI from light ballasts.

 

[Your_account]

I hate that Powerline stuff the interfear my cb radio!!!