FLC OF A B737-700 LOST COMS WITH ARTCC WHEN THEY INADVERTENTLY LOST THE ASSIGNED RADIO FREQ DUE TO IMPROPERLY SWITCHING TO THE USE OF A DIFFERENT RADIO. ANOTHER ACR FLC PROVIDED THE PROPER FREQ WITH WHICH TO REESTABLISH COMS.

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WE WERE ON RADAR VECTORS OFF THE FQM.FQM1 ARR INTO EWR. CTR PUT US ON A HEADING. CAPT WENT OFF #1 RADIOS TO #2 RADIOS TO CALL IN-RANGE. APPROX 10 MINS LATER WHEN CAPT CAME BACK TO TAKE OVER #1 RADIOS I SAID IT SURE SEEMED QUIET. THEN I HEARD OUR OPS ON THE #1 RADIO HEAD. WHEN I LOOKED DOWN THE #1 RADIO HEAD WAS SHOWING OPS FOR THE #2 RADIO. CAPT AND I IMMEDIATELY TRIED VARIOUS CTR FREQS AS SHOWN ON THE HI/LOW ALT CHART. WE WERE UNSUCCESSFUL ON ALL FREQS. I CONTINUED FLYING THE ACFT WHILE HE TRIED MORE FREQS. HE THEN WENT UP TO 121.5 AND AN ACR Y FLT WAS ABLE TO GET US A GOOD FREQ. WE CONTACTED CTR AND RESUMED OUR FLT WITH NO OTHER PROBS. WX WAS CLR AND WE WERE NOT CLOSE TO ANY OTHER ACFT AT ANY TIME AS OBSERVED ON THE TCASII. THE RADIO HEADS IN OUR NEW GENERATION ACFT ARE PRONE TO THIS TYPE OF RADIO HEAD CHANGING (ALL RADIOS CAN BE CTLED FROM 1 HEAD). I FEEL THIS IS A OR COULD BE A BIG SAFETY PROB ESPECIALLY IN BAD WX OR IF SOMEONE INADVERTENTLY PUSHES THE WRONG BUTTON. (RADIO SELECTOR HEADS VERY POORLY DESIGNED.) I HAVE SEEN THIS HAPPEN MANY TIMES BEFORE.