August 19, 2012

Power supply quality impact on RF noise

I suspected that the PSU that came with the MK802 generate a bit of noise so I decided to compare it with a high quality PSU. Measurements with an oscilloscope on the USB port power line indicated that it seem to be true. So I prepared some python scripts to collect RF data from my RTL-SDR device to see how it affected the RF noise. The plot below shows the result. Red is the original power supply for MK802 and the blue is a "Nordic Power" high quality power supply. As seen it does get a few dB better with high quality power supply.

August 7, 2012

RTL-SDR Current Measurement

I was curious to know how much power the RTL-SDR (RTL2832 and E4000) dongle required since the setup in my previous post with an MK802 has limited ability to power USB devices. I modified an hub to break the Vcc line so that I could hook up an multimeter. With the dongle inserted and no software running it showed ~100mA. Running rtl_test with varying sample rate from 1 to 3 MSPS resulted in 180-190mA.