A radio receiver self test system (10) that can test a plurality of bands in duplex cellular phones and other duplex communication devices can be constructed so that it operates during idle time slots. The system can be configured to test the performance of the radio receiver at all ranges of signal levels and in all channels. The system can include a receiver (14) and a transmitter (12) coupled to an antenna (28) and an antenna/noise switch (16). The switch can have as an input, a noise source (18) such as a broadband or thermal noise source. A baseband upconverter/downconverter module (24) can include a processor that provides control signals (27 and 26) for controlling the level of the noise source and for controlling the switch. The system can further include linear amplifier (20) on a receive path and a power amplifier (22) on the transmit path.