Learjet 35
Air Traffic Control Fully Certified
Communication Breakdown
ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued New Clearance
Human Factors; ATC Equipment / Nav Facility / Buildings
I was working SDER. A Lear Jet was inbound to NZY; checked on and I told him 'Roger.' I later issued him a descent to 6;000. I handed him off to SDZR who would be working him into NZY. The SDZR RADAR Controller later called my attention to the fact that the Lear Jet was below the 5;000 FT MVA to the East of PGY. I issued a Low Altitude Alert to the Lear Jet and climbed him from approximately 3;800 back to 5;000. I told him that he had been assigned 6;000. He said he was cleared to 3;000. I later reviewed the audio of the event and although I did issue 6;000; I missed his read back of 3;000. Recommendation: listen for read back. When I first sat down at this sector; a few of the transmissions I made were not acknowledged. I realized that I was transmitting on the primary frequency. I have experienced this issue with this frequency on several occasions. I immediately switched to the backup frequency which seems to work more reliably.
SCT Controller described a below MVA event when issuing the correct descent clearance; but then failed to hear the incorrect read back by the pilot. The reporter listed radio equipment as a possible contributing factor.