Any narrow band FM receiver with an external speaker connections can be used.  However, software control of the receiver from TargetTrack, Signal Track, or the MPT User Interface requires one of the following receivers:
ICOM R1500 ICOM R2500 ICOM R8500 ICOM R8600 ICOM R9500 ICOM R30 AOR SR2200 AOR AR5000 AOR AR5001D AOR AR8600 AOR DV1
Our DF processor has calibration coefficients built in for these receivers as well as the Motorola MCS 2000 transceiver so in mobile applications no calibration is required.