SDR Dongle is Deaf! But wait there is more.....

Sometime ago I built an HF Upconverter to use with my NooElec SDR Dongle. I ran into an interesting scenario. The mixing device is an SA612, the LO signal is provided by an Si5351 Breakout board from Adafruit instead of the traditional 125 Mhz oscillator.

Notice the spectral display with the power brick connected to my Laptop...

...and now without the power brick connected to my Laptop...

Can you see the difference?

The power brick raises the overall noise floor by about 10db across much of the HF spectrum! The overall effect of this was to make the SDR receiver seem pretty deaf to desired signals.

This is a common problem with trying to use switching power supplies in the ham shack. I was able to clean this noise up quite a bit by adding two additional clip-on ferrite rings to the output cable of the power brick. The cable already had one ferrite ring installed by the power supply manufacturer.