During drive test, you can identify the trx on which you are doing the call thanks to the MAIO. Each trx of the cell has a unique MAIO.
only exception : If the hopping mode is “synthetized freq hopping”, and if the call is on the TRX1 (bcch), then you will see a fixed frequency on this TRX. Indeed, the trx1 is not hopping in case of synthetized frequency hopping.
In case of baseband hopping (bbh), the trx1 is hopping like any other trx.
For detailed explanation about hopping, hsn, maio, etc, please use the search function.