the buc and modem of an earth terminal fig1 shows a block diagram of an earth terminal 1 including acu 10 modem 11 and buc 12 the asim processing unit may be incorporated into the modem or the buc for motorized earth terminals the asim processing unit may also be incorporated into the antenna control unit acu in the embodiment shown in fig1 the asim processing unit is incorporated into acu 10 acu 10 communicates with modem 11 via link l 1 with rf power meter 12 via link l 2 with adjustable rf attenuator 13 via link l 3 and with antenna 14 via link l 4 modem 11 transmits rf signals e g data to the antenna through buc 15 and receives rf signals from the antenna through lnb 16 in an embodiment the asim processing unit incorporated into acu 10 periodically executes a routine with steps as shown in fig2 acu 10 sends a query 21 1 to the modem 11 for the transmit symbol rate a query 21 2 to the rf power meter 12 for the rf output power of the buc and a query 21 3 to rf attenuator 13 for the rf attenuation setting of the buc the asim processing unit sends query 21 1 to the.