I once connected a 20-meter end-fed antenna to a building that served a similar purpose as a warehouse at my workplace. The SWR was acceptable, with a noise level of 59+ dB and a spectrum dominated by red. I then tried disconnecting different sources of interference one by one. When I disconnected the power supply for an electric bicycle charger located nearby, everything became quiet, with a background noise level below 53-55 dB. I was also able to hear communication on frequencies such as 7050. This experience made me realize the extent of the problems caused by cheap and poorly designed electric bicycle chargers.
I remember that several years ago, a colleague at my workplace gave me an unused charger. It was heavy and bulky, but inside it was a well-made R-type transformer. Looking at the chargers available today, they are much lighter and smaller than the one I received, and some even don't have a heatsink.
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