AM Radio interference

[kitestrings]

Folks,

I know there are at least some HAM radio enthusiasts here.  I thought this might be an interesting question to pose here.  I'm hoping MaryB is tuned in; pun intended.

I work for a rural cooperative utility.  We use a PLC AMI system.  Basically we manipulate the AC waveform to read across the power line.  We recently had a member with an AM radio describe that he gets interference when we read the meter, or poll the meter.  It is a Grundig portable YB 400 PE, a LW/MW/SW/FM set with several adjustments to signals.  He's tried taking the meter off the line source and operating it with the (optional, 9VDC back up) dry cell batteries, and he still hears the noise.  Is this being picked up inductively somehow with the antenna?  Our normal fixes, short of installing a non-AMI meter, are going to be ineffective if that is the case.

Thanks for any help.  ~ks

[Mary B]

Near field interference... and the PLC might be adding some harmonic trash on the signal... need to check it with a spectrum analyzer and see what is coming out of the meter. You can do a poor mans spectrum analyzer with one of these https://www.ebay.com/itm/RTL-SDR-Blog-V3-RTL2832-1PPM-TCXO-HF-BiasT-SMA-Software-Defined-Radio-Antennas/283144516411?hash=item41ecba733b:g:yKcAAOSwL5BZwksO and appropriate software running on a laptop...

[clockmanFRA]

I use a LW radio receiver tuned to 198kHZ LW, BBC World service in the UK, I am in France so the signal is weak.

Some days I get the BBC, some days I get the Russian service from Moscow a few thousand miles away, as they seem to both share the same frequency.

Anyway, I use the LW radio receiver to listen to a fairly wide band of bleed from electrical installations. Laptops are the worst and bleed all over the place. Mobile phones when being charged are also bad bleeders. Here in France their electrical transmission lines also kick out a fair bit of interference. Just so beautiful when the main utility Power Grid is out, as their is such peace on the airways.

Kitestrings, I actually use the LW receiver method to check my OzInverters  bleeding, and ensure that my shielding steel cabinet is well earthed and doing its stuff.

Modern PSU seem to be the most culprits.

Interference suppression is not my field, but their are specialist's out there that should be able to help.

[Mary B]

Power company guys always have a hard time believing I can narrow down an offending pole 1/2 mile out with my 2 meter antenna array... until I tell them I can hear my own return echo off the moon and that signal is extremely weak! I can usually tell them a group of 3 poles to check, and can narrow it to one pole if I get in my truck and use the HF antenna on the truck to find the noise peak. I called last year and gave them the exact pole. They didn't believe me and had their "expert" come out with a really crappy spectrum analyzer that needs a preamp in front of it. He said nothing wrong, I told him to come in the house and swung the antennas showing the peak and direction and used a compass outside to show the group of poles. Then said get in the truck and listen to this radio as I drive... as I passed the offending pole the signal strength meter spiked to the max...

He said there can't be anything on that pole, I can't see it on my equipment. Well get a truck here and go up there... before the truck arrived the cross tree started on fire and they had to de-energize that entire line to put it out... He is working with me to upgrade his equipment now to something that works.

[DamonHD]

Very good that he paid attention to what worked and is taking advice!

Rgds

Damon

[Mary B]

He covers a 5 state area... and he told the local guys to listen to me I had equipment that was better than his LOL They even called me to locate a noise source in the next town west of me, turned out to NOT be them. Grain elevator had a motor that was sparking to ground... when we showed up and told them they were skeptical but looked. That motor could have caused a grain dust explosion. I made $50 for 25 minutes work...

[DamonHD]

Sounds like you should have made $5k minimum given the costs you saved!

Rgds

Damon

[JW]

I had this ford ranger and when charging my cell phone, I would pick up the duty cycle of the charger the signal would rise and fall and you could hear it on AM stations. I then would send/call re-transmit the interference thru my cell phone voice massage's picking up that audio. The channel sent the interference signal thru voice mail on my cell phone. Once I re-sent that interference thru my cell phone you wouldn't believe the problems that did get me into.

Only picked/happen up on that truck, I tried it in other vehicles it was filtered. You could never hear it.