Hi Chris,
It's typical of a switched mode power supply, which looks to have an approximate 9KHz component.
Maybe a car or mobility scooter charger or Solar PV invertor (if it doesn't go off at night it may be one with a power wall / battery bank), variable speed motor / fan drive, but to be honest it could be almost anything these days.
I'd build a small loop antenna and try to DF the source if possible.
Regards,
Martin
