Using a passive antenna (VE3DO loop) with a Clifton Labs Z10042 11 dB Norton amplifier connected directly to Red Pitaya at N6TV, strong intermodulation from two nearby FM broadcast stations on 92.3 and 106.5 MHz was clearly visible (106.5 - 92.3 = 14.2 MHz):
Inserting the 14:1 transformer between the pre-amp and the Red Pitaya reduced the intermod significantly, and atmospheric band noise (wideband sensitivity) improved by about 4 dB:
Software-defined radio (SDR) is a radio communication system where components that have been traditionally implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented by means of software on a personal computer or embedded system.
A basic SDR system may consist of a personal computer running SDR software that interfaces with analog-to-digital converter over USB or ethernet, preceded by some form of RF front end with RF amplifiers, filters and attenuators.