QRM - USB Charger Plug

One of the more interesting articles in this month's RadCom was a piece about QRM arising from the now very common, essentially zero-cost USB chargers packaged with everything from mobile phones to handheld radios, and which can be used interchangeably on many devices.

Handy device, terrible QRM.

I got out a typical charger, which was supplied with a mobile phone, made in China (of course!), and plugged into the house mains to charge a tablet PC.

The results speak for themselves.  Whilst there was no discernible QRM at 20m, from then on up, it was a very different story, with interference so strong as to make any dubbing of the videos to tell you when the USB charger was on, and when it was off, unnecessary.

Apparently, these devices are meant to operate much more quietly, but circuit omissions are now commonplace such that, once more, the HF bands are under threat from these things, flooding as quickly as they can make them, from China.  The threat is even greater thanks to people's laziness and tendency to leave them permanently switched on.

First, 17m band:

12m band (I lost the 15m vid!):

10m band:

6m band: