Calif. Highway Patrol I-10
As you travel West on I-10 from the AZ/CA state line, the CHP uses 42.44 Base/42.28 mobile 162.2 Hz "Red Channel" for the Blythe #6, Indio #76, and San Gorgonio Pass #97 units for approx. 154 miles from the AZ state line. As you continue W/B the CHP's San Bernardino CHP office starts their jurisdiction at County Line Road (very close to the San Bernardino County Line) and they use 39.68R 118.8 Hz. I've attached a map I created showing info all the way to PCH in L.A.