Pedro's buzz: Or what's common between V02a/SK01 and Radio Habana Cuba

It is a nice, sunny morning (with 31 sunspots... yeah!) with Radio Habana Cuba on 6140 kHz, the same frequency as E25. It appears that the few sunspots helped a little bit and RHC is a bit stronger than usual. RHC is the BC QRM I sometimes mention when talking about E25 on 6140 kHz at ~0800z, and it is usually stronger earlier in the mornings. Today I could hear a buzz, something like the 50 Hz (or 60 Hz? What does Pedro use in Cuba? LOL!) and its harmonics.

I thought: "Let's try a V02a frequency" and decided to tune to 5898 kHz. Success! There was the V02a YL calling! A similar buzz like RHC was heard.

A few moments later, the YL stopped and a SK01 transmission occurred! Another surprise! Then the YL was back! This is the SK01 transmission. Near the end of the recording I switched to 6140 kHz for comparison. The following spectrogram image compares the two "buzzes":

The left half is from a silent part of the Radio Habana Cuba transmission while the right part is from V02a. There are more harmonics apparent in the RHC part since its signal was stronger. But they seem to match, don't they? Or I'm seeing "patterns" here, like most of my fellow daydreamers (i.e. Numbers Stations fans)?

Back to daydreaming...