What's causing these horizontal bands of noise?
It's the middle of the day here in a low density city neighborhood. They were not present about 20 minutes ago; now they are even stronger and filling in the space between the lines.
How do I figure out what these horizontal lines are?
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I've had similar noise multiple times - I've had three sources. One was a light dimmer in another room. Another was the charging circuit in a UPS under the radio bench. The third was a seemingly normal LED light bulb.
The first thing to do is to put the radio on battery power, and turn off the main breaker in your power panel and see if the noise goes away. If so, the source is in your house. If not, then you need to look outside. In my case, it went away, and then the hunt was on to locate it. Try turning each breaker off individually to see what room it is in. I had to result to a 50 foot piece of RG58 with a bit stripped off the end as a sniffer antenna to search around the shack to find the noisy UPS.
For outside searching, I take a portable shortwave receiver outside and hunt for the noise. I've had touch lamps and lamp dimmers in neighbors houses be the culprit. Corona discharge from power lines can sometimes be a problem - does it go away for a while after a good rain? If you can get a bearing with a directional antenna, that's helpful for knowing where to search.
