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KUSC-FM 91.5 has disappeared from the radio dial in San Diego

sdwulfdawg

sdwulfdawg

Anyone notice how KUSC-FM 91.5/Los Angeles has seemingly disappeared? While the signal was always a little brittle and sketchy depending on atmospheric conditions, it really has been obliteraed in metro San Diego....
 
Tropospheric ducting is affecting FM signals. You’ll either get signals better or worse. Last night, the San Diego stations were coming into LA and obliterating the reception of the few translators in the area.
 
Tropospheric ducting occurs when there is a significant temperature inversion, the point at which a lower layer of cooler air is held in place by an upper layer of warmer air. This zone is generally centered at around 2000 ft. FM and TV signals see this as a mirror (imagine this as if it were the inside of sphere) and can refract back down to earth way beyond the stations' normal line-of-sight coverage. KUSC however is actually above the normal inversion layer. The station is on Mt. Harvard very near Mt Wilson which is about 5000 ft above sea level. KUSC's signal can bounce off of the inversion layer and seem much weaker in San Diego, during a strong inversion. You might notice for example LA's 98.7 is very strong when 91.5 is weak. KYSR 98.7 is in the Hills above Coldwater Canyon at about 1500 ft which is a perfect elevation for strong Summertime tropospheric ducting. Sometimes though the inversion is a lot higher. I used to live about 75 miles north of San Francisco, and at times I could hear 103.3 from Santa Barbara. (4000 ft with 105 kw) during strong inversions.
 
I tuned into KUSC 91.5 tonight while driving around San Diego, and signal strength was about what it's always been. So if they had a problem, it's been corrected.
 
I sometimes listen to KUSC on the way home from work. I work near the 163, Kearny Mesa and travel up the 15 towards Rancho Bernardo. Pretty much a strong signal all the way
 
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