Abstract: A portable radio is provided that performs an impedance measurement to determine a radio frequency (RF) load type connected to an antenna port of the portable radio. The portable radio includes an impedance measurement circuit and a tunable matching circuit operatively coupled thereto through an RF switch A sweep generator injects an LMR frequency sweep to the RF load during non-transmit or non-receive time slots for the impedance measurement. The tunable matching circuit is configured as a radio frequency (RF) bypass during the impedance measurement, thereby enabling the impedance measurement circuit to directly measure the impedance of the RF load coupled to the RF port and identify the RF load as either a land mobile radio (LMR) antenna or equipment (wideband load). When the RF load is determined to be an LMR antenna, then the matching circuitry is tuned for the identified antenna. When the RF load is determined to be wideband equipment, then the matching circuitry remains bypassed.