CPR RPTR LOST COM WITH THE TWR WHILE HOLDING IN POS ON RWY 17 AND HEARD AN ACFT ON FINAL FOR THE SAME RWY DECLARE A GAR. AFTER MOVING THE ACFT A FEW FT; RPTR HEARD THE TWR SAY THAT TKOF CLRNC HAD BEEN GIVEN TWICE AND MADE MENTION OF THE ACFT BEING IN A DEAD SPOT ALLEGING THE LOST COM SIT OCCURS ABOUT ONCE A MONTH.

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WE WERE INSTRUCTED BY THE PHL TWR TO TAXI INTO POS AND HOLD ON RWY 17 PRIOR TO OUR DEP TO RKD (FULL LENGTH). WE WERE ALSO ADVISED BY THE TWR OF AN ACFT ON FINAL APCH FOR RWY 17. I BELIEVE IT WAS A REGIONAL AIRLINE TURBOPROP. AFTER LINING UP ON RWY 17 AND WHILE HOLDING IN POS; THE TWR INSTRUCTED US TO BE PREPARED FOR AN IMMEDIATE TKOF. DURING THIS XMISSION FROM THE TWR I NOTICED THE QUALITY OF HIS RADIO XMITTER HAD DETERIORATED. HE WAS STILL QUITE READABLE; HOWEVER. I THOUGHT FOR A MOMENT OF MOVING MY ACFT UP THE RWY SEVERAL FT; SUSPECTING I WAS PARKED IN A 'DEAD SPOT' BUT I WAS AFRAID IT MIGHT GET WORSE INSTEAD OF BETTER; SO I STAYED PUT. THEN I HEARD THE REGIONAL AIRLINER DECLARE A GAR AND SAW HIM PASS OVERHEAD (AT A SAFE ALT). AT THIS POINT I MOVED UP SEVERAL FT AND HELD THE SQUELCH SWITCH UP ON MY RECEIVER AND HEARD THE TWR CALLING ME. HE SAID HE HAD CLRED ME TO TAKE OFF TWICE BUT THAT WE MUST HAVE BEEN IN THE DEAD SPOT. HE SAID IT HAPPENS ON RWY 17 EVERY SO OFTEN; ABOUT ONCE A MONTH; HE SAID. OUR DEP THEN PROCEEDED WITHOUT FURTHER INCIDENT. I FEEL THAT THE WEAK RADIO RECEPTION IN THE AREA ON RWY 17 WHERE WE WERE HOLDING IN POS IS A POTENTIAL UNSAFE SIT AND SHOULD BE CORRECTED. I'VE SEEN DEAD SPOTS OF POOR RADIO RECEPTION WHILE TAXIING ON LARGE ARPTS BEFORE; BUT I'VE NEVER HAD ONE ON AN ACTIVE RWY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THERE WAS NO FOLLOW-UP CALL TO THE FACILITY TO LEARN MORE ABOUT THE BLIND/DEAD SPOT REFERRED TO IN THE RPT. RPTR SAID THAT DURING THEIR CLBOUT ANOTHER ACFT MADE A COMMENT THAT IT WAS A SMALL SPOT.