AN MU300 DIAMOND JET LOSES COM WITH ZLA WHILE IMC ON A DEP FROM LAS. THE FAULTY RADOME GROUNDING WAS CREATING STATIC THAT PREVENTED 2-WAY COM.

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AFTER DEP FROM LAS; WE WERE CLBING TO FL230 ON THE SID. IMMEDIATELY UPON ENTERING THE OVCST AT APPROX 15000 FT; BOTH COMS RECEIVERS EMITTED A LOUD STATIC SOUND AND WE COULD NO LONGER HEAR ATC. WE HAD EXPERIENCED THIS PROB TO A LESSER DEG SEVERAL WKS PRIOR. IN THAT INSTANCE; WE WERE STILL ABLE TO HEAR ATC WITH SOME DIFFICULTY AND FOUND THAT THE PROB DISAPPEARED WHEN REACHING CLR SKIES ABOVE THE CLOUDS. THE ACFT AT THAT TIME WAS INSPECTED AND THE RADOME GROUNDING WAS DETERMINED TO BE THE PROB. THE RADOME WAS SENT IN FOR REPAIRS AND A 'LOANER' UNIT WAS INSTALLED FOR OUR USE. WHEN WE REACHED OUR CLRED ALT OF FL230 WE WERE STILL IMC AND COULD NOT RECEIVE. OUR ORIGINAL CLRNC HAD BEEN TO EXPECT FL330 2 MINS AFTER DEP SO WE SET CODE 7600 IN OUR XPONDER AND ANNOUNCED 'IN THE BLIND' THAT WE WERE STARTING A CLB TO FL330. AT THAT POINT; RECEPTION HAD IMPROVED AND WE COULD HEAR ATC WITH SOME DIFFICULTY. AFTER SEVERAL MINS; ATC CLRED US TO FL330 AND WE BEGAN OUR CLB. AS BEFORE ONCE ON TOP; OUR RECEPTION WAS FINE. APPARENTLY THE 'LOANER' RADOME WE RECEIVED WAS WORSE THAN THE ORIGINAL. A LACK OF IMC PREVENTED A PROPER CHK AT INSTALLATION.