A control apparatus configured to determine calibration values for a radio frequency apparatus comprising means for transmitting coupled to an antenna through means for antenna tuning, the control apparatus being configured to determine the calibration values for the radio frequency apparatus based on at least two impedance measurements and based on at least two antenna tuner configurations, wherein the control apparatus further comprising: means for setting different antenna tuner configurations at the means for antenna tuning; means for receiving feedback being configured to carry out impedance measurements between the means for transmitting and the antenna; and means for processing coupled to the means for setting and the means for receiving, wherein the means for processing is configured to: obtain a first impedance measurement using the means for receiving based on a first antenna tuner configuration; obtain a second impedance measurement using the means for receiving based on a second antenna tuner configuration; determine a first gamma value and a second gamma value based on the first impedance measurement and the second impedance measurement, respectively; apply at least one of an estimated crosstalk correction, an estimated phase correction, and an estimated magnitude correction to the first gamma value and the second gamma value to obtain a corrected first gamma value and a corrected second gamma value, respectively; determine a first load impedance value based on the corrected first gamma value and the first antenna tuner configuration; determine a first expected impedance based on the first load impedance value and the second antenna tuner configuration; determine a first difference between the first expected impedance and the corrected second gamma value; and determine the calibration values based on the first difference. means for setting different antenna tuner configurations at the means for antenna tuning; means for receiving feedback being configured to carry out impedance measurements between the means for transmitting and the antenna; and means for processing coupled to the means for setting and the means for receiving, wherein the means for processing is configured to: obtain a first impedance measurement using the means for receiving based on a first antenna tuner configuration; obtain a second impedance measurement using the means for receiving based on a second antenna tuner configuration; determine a first gamma value and a second gamma value based on the first impedance measurement and the second impedance measurement, respectively; apply at least one of an estimated crosstalk correction, an estimated phase correction, and an estimated magnitude correction to the first gamma value and the second gamma value to obtain a corrected first gamma value and a corrected second gamma value, respectively; determine a first load impedance value based on the corrected first gamma value and the first antenna tuner configuration; determine a first expected impedance based on the first load impedance value and the second antenna tuner configuration; determine a first difference between the first expected impedance and the corrected second gamma value; and determine the calibration values based on the first difference. obtain a first impedance measurement using the means for receiving based on a first antenna tuner configuration; obtain a second impedance measurement using the means for receiving based on a second antenna tuner configuration; determine a first gamma value and a second gamma value based on the first impedance measurement and the second impedance measurement, respectively; apply at least one of an estimated crosstalk correction, an estimated phase correction, and an estimated magnitude correction to the first gamma value and the second gamma value to obtain a corrected first gamma value and a corrected second gamma value, respectively; determine a first load impedance value based on the corrected first gamma value and the first antenna tuner configuration; determine a first expected impedance based on the first load impedance value and the second antenna tuner configuration; determine a first difference between the first expected impedance and the corrected second gamma value; and determine the calibration values based on the first difference.