My local NPR station broadcasts at 910 AM, and there’s an intersection near my house where I get very poor reception. There are lots of high-voltage lines in that area.
This thread reminds me of a job I had in the late 1980s. I was a data entry operator, and we could have radios at work. The NPR affiliate there that broadcasted “All Things Considered” was at 640 AM, and if my boss was running the printer, I couldn’t listen to it because that printer interfered with just that frequency. I hadn’t thought about that in ages.
I’m about half way between the Maroubra and Sydney dots. So the nearest transmitters are the cluster at Sydney Olympic Park. I’m sure they have not moved in decades.
OK, I just tried the portable radio location method.
It’s not too bad today which makes it difficult to get a fix on it. But it seems to be coming either from within our house, or the terrace next door (ours is the end of a row of terraces). In the lane next to our house (ie on the opposite side to the neighbour’s terrace) there was virtually no interference.
I thought it might be the wifi, but turning off the one in the kitchen made no difference. I’ll have to wait until I’m the only one home and try turning everything off, I guess.
I’ve had similar issues in our house with FM radio, which was ultimately cured by fitting ferrite chokes over the cables to all the CFL light bulbs and the central heating pump. This noise would undoubtedly have been even worse on AM, but I never listen to AM so I wouldn’t have noticed.
I was also tasked with dealing with a similar issue at a client’s workplace, where they had an unfortunate policy of mixing up the office, production and lab spaces. There was a laser range lab setup that had sensitive electronics that was picking up noise, and no-one could work out where the noise was coming from. We had spectrum analysers and directional antennae, but the noise was below the specified band of even the biggest antenna so in the end I borrowed a battered AM radio from Production, tuned it in to the peak frequency of the noise and wandered around listening to it. The source of the noise seemed to be a big electrical junction box, and most of the cables that connected to it, so that was only partly helpful.
In the end the noise was traced to a robot arm. This was only found by someone coming in during the weekend and turning off power to each area of the site in turn. Sometimes you can’t beat a nice simple process of elimination.
I’m an amateur radio operator and this type of thing comes up frequently in our community. I can say that I discovered two items in my house that seemed designed to kill HF radio reception: A sealed lead acid battery charger and an ionic air freshener/dust filter. The high voltage air freshener dealie isn’t a big surprise but the battery charger took a while to figure out.
The charging circuit in one of my laptops throws off a bunch of RF but needs to be in pretty close proximity to be noticeable. It isn’t just the AC adapter, it is fromt he laptop when the adapter is connected.
I finally got an opportunity to look at this again yesterday. Flicked off every switch in the fuseboxes, so no power to anything in the house. The interference was unchanged! So it’s not us.
Then I walked around with a battery radio, and with a bit of (very) rough triangulation I think the source is in the neighbour’s house, possibly only a metre or so from the mutual wall. Oddly though it’s a hallway there IIRC … I’ll have to check it out next time I’m in there.
What I didn’t mention before is there’s also a mechanical noise we hear, which also appears to be coming from next door. Possible even the same area as the interference, although it’s one of those sounds which are maddeningly hard to pin down, wherever you listen to it it seems to be coming from somewhere else. It was a regular low pulsing sound with a period of about 3 or 4 seconds. But recently it’s got louder, higher-pitched, and not so regular. It sounds like some sort of pump or slow motor, but it’s hard to imagine what for. And the neighbours don’t hear it, they say … !
The shower, for one. And my partner likes having it on while she’s pottering around her studio, the radio is just better placed to get the sound to her there.
We believe we have traced the mechanical noise down. There’s a rainwater system in the back yard, and the noise appears to be come from one of the pumps associated with that. You can actually feel vibration in that pump. The weird thing is, though, that disconnecting that pump from power does not change the noise … in fact when we turned off all power to the house it kept going.
And that pump is nowhere near the apparent source of the electrical interference … !
Neighbor may be operating a hydroponic grow box to grow… tomatoes. Those boxes, and other indoor gardening equipment, generate an AM signal.
I read a blog post on some cops-only website (no, I’m not a cop) by a cop whose blog is entitled “The Drug Warrior.” He advised cops to drive past suspected grow houses with the AM radio on. If there’s interference, he goes to the door and starts asking questions.
Two or so weeks ago we evicted the tenant downstairs unit within our house and started renovating, which included replacing just about everything electrical like halogen lights, range hood, bathroom fan and so on.
A week ago I turned on my shower radio for the first time in a couple of months … no interference at all! Still none today, which is by far the longest period without it since it started.
If it was really caused by something downstairs, I can’t understand why it apparently moved around …
