About three months ago, I finally put up another 20m antenna—an end-fed, half-wave antenna. Right off the bat, I was flummoxed (I love that word) by the high noise level. It was nearly S9, obliterating all but the strongest signals.
I thought it had to be something to do with the antenna. I was not experiencing any noise on any of the other bands, after all.
As it turns out, though, the source of the noise is the laptop power supply. I had taken the laptop somewhere on Wednesday, and when I returned it to the shack that evening, I switched the rig over to 20m before connecting the power supply back to the laptop. No noise! When I plugged the power supply into the laptop, the noise jumped up to S9 again.
What’s really confusing about all this is that I don’t hear this noise on any other band. They’re all completely quiet. Like I’ve said before, sometimes 40m is so quiet that I wonder if the antenna is even connected.
At any rate, the last couple of days, I’ve been working 20m with the power supply disconnected, running the laptop off the battery, and the results have been quite good. This evening, for example, I worked several DX stations, including 6W/HA0NAR in Senegal.