About five days back, I noted this extensive noise across the 15 meter amateur radio band. It persisted for quite some time and then subsided. I was using my modified 40 m inverted V antenna on 21 MHz, presuming that it will resonate as third harmonic.
I had taken only the picture of the waterfall for the heavy noise. Shall try recording audio next time, if I come across similar QRM. 73 Bob. de Jon, VU2JO
First impression, looks to me as a free running oscillator. Could for instance be caused by local solar panel equipement. However in such case one would exspect it to be a repeating phenomena throughout the spectrum over a wide bandwitdh ( e.g. every 200Khz increase ) 73's, Frank, de PA3GCJ
Thanks for the input Frank. I shall observe this further keeping this information in mind, at least for academic interest. There is a solar panel at a nearby home, which I can't do anything about! 73 de Jon, VU2JO
As you most likely know, solar panel systems often come with pcb's called optimizers to evenout disbalance between panels. These optimizers often run with free running (unstable ) oscilators --> recognizable due to this frequency instabilities. I'm no expert on solar systems but can imagine some ferrite beads on the cabling close tot these optimizers helps avoiding radiation cause by common mode currents on these lines. It is an relative inexpensive solution which needs no electical physical altering of the solar system. ( wide variety of cheap beads in several sizes can be found online these days )
