Coincident with the start of our house extension, the power supply in my PC stopped working. I replaced it with one bought from Maplin. Around the same time, I built another PC for my son's birthday, using a case from a local computer shop that now isn't trading. When I became QRV again I discovered that the power supplies in both PCs were injecting a lot of noise into the mains wiring, mainly on the LF bands. It's easy to establish if it's the PC power supply by pulling the mains lead out the socket. Note that simply turning the PC off isn't enough, because of the way the on/off button is detected.

Further investigation revealed that on both units, where the filter components should have been, there were none! See the photos below:




And here's a close-up of the Q-TEC unit:



Notice that both units are CE marked, which means they would have needed the filter components to pass EMC regulations on the units offered for certification. Clearly, the manufacturers thought nobody would notice, and they could increase their profit margins!

Probably, I should have complained to Maplin or Trading Standards, but by the time I discovered the issue a year had passed and I certainly no longer had proof of purchase.

I ended up replacing these power supplies with PW-5150 units manufactured by Trust, rather than some unknown OEM. It seems you can actually trust them because they do have the filter components fitted (see photo below).



Not only are these components fitted, but there is also an additional filter attached to the IEC power socket.

One wonders how many PCs are out there polluting the HF spectrum. Fortunately, the rise of the laptop has been good in this respect because I have yet to find a noisy laptop power adapter. I have since upgraded to a Shuttle XPC, which also doesn't have any noticeable noise issues.