Cube emits startup tone in Amateur Radio Band (143 MHz)

#1

Trying to find the reason behind a phenomenon we noticed recently. If I switch on the Cube near a VHF Radio, I can listen to the Ardupilot Startup tone in 143 Mhz Band ( 2 meter Band).
I have tested it on a standalone cube. The transmission power is very low in this setup.
When I connect an ESC the signal gets amplified. I’ve recorded some cases of the same in the video below.
https://youtu.be/25Y53n-xYY4

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#2

The fun is, the emissions are seen clearly at every regular intervals, like 140.3MHz, 141.3MHz, 142.3MHz…
The modulation is WFM…and the antenna is poor and hence needed to be kept near the Cube/Esc. Also noticed a regular disturbance in the spectrum that persists after the Cube boots up!

We did try it with a MatekF405SD board and the sounds aren’t on the spectrum!