Hardware AGC in RTL-SDR devices

I was testing the Gqrx FM stereo code by Alex Grinkov using an RTL-SDR dongle when I noticed that the recently added auto-gain in the driver can be quite useful.

The video below shows a portion of the FM broadcast band with one of the strongest stations around. Due to very strong broadcast FM signals, there are several intermodulation products in the passband when the device gain is set to maximum. Enabling the automatic gain reduces the gain and eliminates the IMDs.

Watch video on Youtube.

Author: Alexandru Csete

Embedded software engineer in the satcom industry during the day. Radio amateur and SDR hacker during the night.