A CORPORATE JET WAS IN POS FOR DEP; WHEN A LIGHT ACFT APCHED; OPPOSITE DIRECTION; AND LANDED. THE CORPORATE JET'S FLC; WAS OPERATING THE COM RADIOS; INCORRECTLY AND; ALSO; FAILED TO SEE THE INBOUND TFC; WHEN THEY TAXIED ONTO THE RWY.

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WE COMPLETED THE BEFORE TKOF CHKLIST; AND SET UP THE RADIOS FOR THE SHORT FLT TO OUR HOME BASE; APPROX 8 MINS AWAY. WE MADE AN ANNOUNCEMENT THAT WE WERE TAKING THE ACTIVE RWY 18; FOR DEP; AND CHKED BOTH THE APCH AND DEPT ENDS FOR TFC. WE TAXIED INTO POS; AND BEGAN THE FINAL TKOF CHKLIST ITEMS. IT WAS AT THIS POINT; THAT WE NOTICED A LIGHT ACFT ON VERY SHORT FINAL FOR THE OPPOSITE RWY. THE LIGHT ACFT BEHIND US; TAXIED UP TO THE HOLD LINE. THIS LEFT US NO WHERE TO GO; AS THE NEAREST TXWY WAS AT THE MID POINT OF THE RUNWAY. WE MOVED AS FAR AS POSSIBLE TO THE L OF THE RWY; AND WERE PREPARED TO TAKE IT ONTO THE GRASS IF NECESSARY. AT THIS TIME I NOTICED THAT COM RADIO #1; WAS SET TO THE ATIS FREQ FOR THE DEST ARPT; COM RADIO #2; WAS SET TO THE UNICOM FREQ; BUT MY ISOAMPLIFIER WAS SET TO XMIT AND RECEIVE ON COM RADIO #1. WE ALWAYS USE COM RADIO #2; AS PRIMARY. THE ISOAMPLIFIER POS WAS NOT CHANGED FROM THE INBOUND FLT; WHEN THE CAPT WAS WORKING APCH; AND I WAS WORKING UNICOM; I HAD INADVERTENTLY SWITCHED COM RADIO #1; FROM UNICOM; TO THE ATIS FREQ; IN PREPARATION FOR THE SHORT FLT; THINKING THAT I WAS XMITTING AND RECEIVING ON COM RADIO #2. MY FOCUS WAS ON THE PREPARATION FOR THE SHORT FLT AHEAD; AND ALL THAT MUST BE ACCOMPLISHED. IN THE FUTURE; I WILL CONFIRM EXACTLY WHICH COM MY ISOAMPLIFIER IS SET FOR; YOU CAN BE SURE. THE LIGHT ACFT LANDED AND CLRED MID-FIELD.