LEARJET 31 FLC QUESTION THEIR ALT CLRNC GIVEN BY APCH CTLR SINCE IT APPEARED TOO LOW FOR TERRAIN OBSTACLE CLRNC.

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WE WERE ENROUTE TO LIVERMORE; CA; WHEN OAKLAND CENTER TOLD US TO FLY OUTBOUND FROM SAC VOR ON THE 157 DEG RADIAL TO TRACY INTXN THEN DIRECT LVK ARPT. WE WERE BEING CLRED DOWN TO LOWER ALTITUDES AS WE CARRIED OUT THE FLT VIA THE NEW ROUTE CLRNC. WHILE TRACKING OUTBOUND FROM SAC VOR ON THE 157 DEG RADIAL WE WERE CLRED TO 5000 FT THEN SOON AFTER DOWN TO 3000 FT. SHORTLY AFTER WE WERE TOLD TO CONTACT BAY APCH. WE ALSO HAD 3000 FT SET IN THE ALT REMINDER BEFORE CONTACTING BAY APCH. WE WERE NOW LEVEL AT 3000 FT. WE BOTH NOTICED SOME VERY TALL ANTENNA TWRS SLIGHTLY EAST OF OUR COURSE AND AT WHAT SEEMED TO BE AN ALT VERY CLOSE TO OURS. THEY SEEMED TO BE LOWER; BUT NOT MUCH! SHORTLY AFTER CHECKING ON WITH BAY APCH THE CLTR TOLD US TO CLIMB AND MAINTAIN 4000 FT. WE DID THIS AND I QUESTIONED THE CTLR ABOUT OUR PREVIOUS CLRNC TO 3000 FT. HE SAID; 'AS FAR AS HE COULD TELL;' WE WERE CLRED TO 3000 FT PREVIOUSLY. MYSELF AND MY COPLT WERE CERTAIN WE HAD BEEN PREVIOUSLY CLRED TO 3000 FT AS WELL. DID THE PREVIOUS CENTER CTLR MISTAKENLY CLR US DOWN TO 3000 FT? I'M NOT SURE; BUT WE WERE BOTH PRETTY CERTAIN ABOUT THE CLRNC TO 3000 FT BY THE CENTER CTLR. MY COPLT AND I DISCUSSED THIS AFTER THE FLT AND THOUGHT MAYBE 3000 FT WAS OK IF THE CTLR IN OAKLAND CENTER THOUGHT WE WOULD GET A VISUAL? MAYBE THE APCH CTLR HAD TO CLIMB US BACK UP TO 4000 FT SINCE HE KNEW IT WOULD BE NECESSARY FOR US TO FLY THE ILS; TO GET INTO LVK; IN THE HAZE? THE APCH AND LNDG WERE UNEVENTFUL AND THE APCH CTLR NEVER SAID ANOTHER WORD ABOUT IT.