EVASIVE ACTION GAR REQUIRED WHEN AN ACFT IN POS COULD NOT HEAR ATCT TKOF INSTRUCTIONS.

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I WAS INSTRUCTED TO TAXI INTO 'POS AND HOLD' ON RWY 4R AT EWR AND WAS ALSO TOLD THAT AN ACFT WAS ON A 7 MI FINAL FOR THAT RWY. WHEN ONCE ON THE RWY; WE HEARD ONLY BROKEN RADIO RECEPTION FROM THE TWR. NOT KNOWING IF THE BROADCAST WAS FOR US; WE HELD OUR POS READY FOR TKOF. WE CHANGED RADIOS; BUT IT DID NOT PROVE TO SOLVE THE PROB. BY HOLDING DOWN THE SQUELCH BUTTON ON THE RADIO; WE HEARD THE TWR INSTRUCTING ACR Y TO GAR. OUR COMPANY DOES REPEATED FLTS; WITH A FLEET OF 17 ACFT; TO EWR. ON A CONSISTENT BASIS; PARTICULARLY WHEN DEPARTING EITHER RWYS 4L OR 4R; THE RECEPTION OF THE TWR IS BROKEN AND DIFFICULT TO INTERPRET. WE FINALLY HEARD AN ACR B737 BEHIND US REMARK TO THE TWR 'I DON'T THINK HE CAN HEAR YOU.' SHORTLY THEREAFTER; WE HEARD OUR TKOF CLRNC; BROKEN; BUT WERE ABLE TO INTERPRET. WE DEPARTED AND; ONCE AIRBORNE; THE TWR RECEPTION WAS CLR. WE APOLOGIZED FOR THE GAR; BUT DID NOT HEAR ANY TKOF CLRNC PRIOR TO THE GAR INSTRUCTIONS ISSUED TO ACR Y. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR FLIES THE FALCON 20 IN A FREIGHTER CONFIGN. THE ACFT HAVE 2 VHF ANTENNAS; BOTH ON THE VERT STABILIZER. THE RPTR SWITCHED RADIOS DURING THIS INCIDENT WITH NO CHANGE IN RECEPTION. THIS PROB WAS WRITTEN UP IN THE LOGBOOK; AND WAS SIGNED OFF AS 'GND CHK OK.' THE RPTR HAS NOT HAD THIS PROB AT ANY OTHER ARPT AND HAS NEVER HAD THIS PROB ON OTHER RWYS AT EWR; ONLY RWYS 4 WHILE WAITING FOR TKOF OR ROLLING OUT. HE HAS HAD NO PROB WHILE ON APCH TO RWYS 4 AT EWR.