HELI PLT HAVING COM DIFFICULTY DEPARTS WITHOUT CLRNC.

Narrative

DURING THE DAY AT BROWN FIELD; I DID SOME PRACTICE AUTOROTATIONS ON TXWY 'D.' I HAD TO SHARE WITH AN ASTRA HELI; AND HEARD ALL OF HIS XMISSIONS TO THE TWR. HOWEVER; LATER ON THAT AFTERNOON; I HAD TO SHARE WITH 2 MIL HELIS. I NEVER HEARD ANY OF THE XMISSIONS TO THE TWR FROM THEM. I RETURNED TO THE RAMP AND WAITED FOR DEP. AS I SAT ON THE RAMP; I OBSERVED AN INS HELI GO THROUGH ITS ROUTINE BEFORE PATROL; AND AGAIN I HEARD NO RADIO COM TO THE TWR. AT APPROX XA45 HRS I STARTED MY ACFT TURNED ON AVIONICS; DID MY CHKS AND CALLED THE TWR. I RECEIVED NO RESPONSE. ALL THROUGHOUT MY WARMUP CHKS; I HEARD NO RADIO CHATTER. AGAIN I CALLED THE TWR WITH NO RESPONSE. I SPOOLED UP TO TKOF PWR AND LIFTED TO A HOVER. I MADE A 90 DEG R TURN TO LOOK DOWN THE TXWY FOR TFC. I NOTICED NO TFC AND NO LIGHTS IN THE CTL TWR. I RPTED I WAS DEPARTING FROM THE TXWY; AND GOT NO RESPONSE. I DEPARTED TO THE WEST AND AS I WAS READY TO TURN NBOUND; I OBSERVED A SET OF ACFT LIGHTS ABOVE AND TO MY R. AS I COULD SEE THERE WAS SEPARATION I CONTINUED MY TURN. SHORTLY AFTER I COMPLETED MY TURN; THE TWR CALLED ME TO SAY THAT A COAST GUARD ACFT HAD JUST DEPARTED. I ASKED IF THE TWR HAD HEARD ANY OF MY XMISSIONS; AND HE RESPONDED THAT HE HEARD SOMETHING; BUT IT WAS GARBLED. I CONTINUED MY FLT THROUGH LINDBERGH'S AIRSPACE AND UP THE COAST; WITH NO RADIO PROBS. I DON'T UNDERSTAND HOW WE COULD NOT HAVE BEEN HEARD; AND NOT HEARD ANY XMISSIONS; UNLESS TWR WAS ON MIL FREQ AND NOT HEARD US. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THERE WERE NO PROBS FOUND WITH HIS RADIOS. HE HAS NO IDEA WHY HE WAS NOT HEARD. THERE HAS BEEN NO FOLLOW UP OF ANY KIND.