I took my portable radio outside, and it sounds just as loud. I didn't walk very far away from the house, but I'm thinking it's coming from outdoors somewhere.
You'd be surprised at how far RFI can travel that's caused by a bad connection up on a utility pole. I've seen some well over a mile away.
I've found a lot of noisy poles using a simple AM Broadcast transistor radio. Many of them become really noisy when you are standing at the pole with the bad connection. A simple tap or smack of the pole will often change the RFI noise or even eliminate it for a few seconds.
Most power companies have RFI troubleshooters that will come out and find RFI sources if you report them once you are certain it's something on their power grid. The guy here often uses an ultrasonic receiver and headphones hooked to a small handheld parabolic dish and can pretty much identify the pole that's causing the noise. And from a decent distance away at that.
If you keep an eye on your noise, see if it does not stop when it rains. I've had RFI from poles that went away at night when the humidity rose each night but made the radio unusable during the day when the humidity levels would drop back down after sunrise.
If you find that your noise goes away when it rains, that's usually a sure sign it's arcing up on a pole somewhere. Sometimes the arcing is enough that you can see it by eye at night but that's not always the case.
It does not take much to create all kinds of noise in a radio!
Most utility companies will actively come out and find and repair these issues as it can save them money by preventing a larger problem should something burn open and cause an outage or create a repair job that can take hours to repair.
I'm pretty sure they must try to find and fix these things when it's wiping out AM Broadcast radio reception as well.
I've had some poles with connections so bad that it was wiping out reception up into the UHF ranges.
I had a VHF repeater at my workplace that I could talk on from home. When a pole became noisy, it would wipe out my repeaters signal. Even the county police had issues back when they were still using analog VHF radios. The officers usually had no clue why their radios would stop working in some areas where they normally worked fine.
I used to walk the powerlines with my little AM radio until the noise became really bad. I knew I was close to the source at that point. That's when I'd hit the pole with a heavy stick or something (not very hard) and could hear the noise change or even stop. Once you find that, you are usually very close and can tell the repair person where the noise is coming from. I don't think I'd mention hitting the pole with a large stick though! Even though I've seen the repair guys use the same tricks before by hitting poles with a hammer or shaking them if they are guyed on one side by shaking the guy wire(s).
Most of them have professional equipment to help find the source of noise but not always. And some power companies may not respond for months.
I've always been lucky and the companies noise finder guy would try to come out the same day many times. He'd even hook his equipment to my antennas coax feed to make sure he was hearing the same noise. This guy gave me his cell phone number so I could call him when the noise started up when it was very intermittent noise that came and went.
We have Ameren Electric here and the noise troubleshooter will find the source and then open a ticket for a repair crew who usually responds in a week or less.
Check that rain thing though and see if your noise does not change in strength or stop all together when it's raining out pretty good. The rain makes an arcing connection actually connect and the noise will stop but return when things dry out after it's stopped raining.
I've even had vines cause all kinds of RFI before but they'd fix themselves when they would burn dry and stop conducting. Hopefully before they cause an actual fire.
