CITABRIA INSTRUCTOR; WITH TRAINEE; BELIEVED THAT HE WAS CLRED FOR TKOF AT A 3000 FT RWY INTXN WHEN HE OBSERVED A MIL RC135 RUNNING UP ENGS FOR TKOF AT THE END OF THE RWY. HE IMMEDIATELY TURNED AND CLRED THE RWY AND AT THE SAME TIME THE TWR CTLR INSTRUCTED THE RC135 TO ABORT TKOF AND THE RPTR TO CLR THE RWY.

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RUN-UP WAS ACCOMPLISHED ON TXWY M; 3000 FT FROM END OF RWY 30. CLRNC COPIED FROM GND; SWITCHED TO TWR FREQ FOR TKOF CLRNC. ACKNOWLEDGED TWR'S HOLD INSTRUCTIONS. RADIO RECEPTION WAS MARGINAL. ACKNOWLEDGED TKOF INSTRUCTIONS FROM TWR AND STARTED TO TAKE THE RWY. AS I CROSSED THE EDGE OF 300 FT WIDE RWY AND PAST THE SNOW PILE; I SAW RC 135 RUNNING UP ENGS AT THE E END OF 11700 FT RWY. I STOPPED IMMEDIATELY THEN BEGAN AN EXPEDITED 180 DEG TURN BACK ONTO TXWY. TWR CALLED AN ABORT TO THE RC135 AS I STOPPED; THEN REQUESTED I CLR THE RWY IMMEDIATELY; BY WHICH TIME I WAS ALREADY CLR. POOR RADIO RECEPTION AND SNOW BANK TOO HIGH TO PROVIDE VISUAL REF TO RWY WERE THE MAIN FACTORS FOR THE CITABRIA. VIGILANCE FROM TWR AND GND FOR THE ONLY 2 ACFT MOVING. CONTRIBUTING FACTOR: WE TAXIED APPROX 100 FT TO VISUAL POINT WITHOUT ATTRACTING ATTN. I AM WELL AWARE THAT WE HAVE TRAINEES AND OPERATED ACCORDINGLY. I HAD NOT HEARD ANY XMISSIONS TO THE RC135 AND ASSUMED I WAS THE ONLY ACFT FLYING AND STARTED MOVEMENT ON SOMEONE ELSE'S CLRNC. I HAD THOUGHT RWY INCURSIONS WERE NOT POSSIBLE -- NOW I KNOW! AUTOMOBILES WERE MADE AWARE OF THE SNOW BANK THAT IS NO PROB TO LARGE ACFT.