RTL2832 receiver overload

December 20, 2015

In high RF environments, you might notice false spurs in the spectrum. Tuning to a false frequency you might hear very distorted or whining audio.

false image spectrum due to strong signal overloading of the RTL2832. Bandwidth 240kHz. True signal is surrounded by false peaks.

RTL2832 Receiver RF overload fixes:

• add bandpass RF filtering if you have a narrow frequency range of interest, or use lowpass/highpass filters as appropriate.
• You might find decreasing RF/LNA gain slightly increases net sensitivity.
• You can use a directional antenna. Compact log periodic (broadband) antennas made from a PCB are available.

Normal, non-overloaded RTL2382 spectrum display has residual center peak from a noisy power supply.

There is a remnant image on the left, due to IQ imbalance. The central hump is due to noisy onboard/PC power supply and remnant DC offset.