First, I-10 between Phoenix and Palm Springs is not "desolate".
Once you leave Buckeye and till you get to Quartzite you are in the ever-fringier signal area of the Phoenix stations.
There is a portion of the trip (about 50 miles) during which you don't see much from the freeway but there are small communities located off the freeway (not large enough to host radio stations though). One you hit Quartzite heading west there are a solid stream of small communities all the way into the L.A. basin
Those little communities between the PHX uban area are truly tiny, often a collection of mobile homes and RV units.
Then there is tiny Quartzite and very small Blythe (where the local AM could not make money and turned in its license) and then there are 140 miles of nothing except a state prison and the nearing-zero population Desert Center. Then you get to the Palm Springs / Coachella Valley metro, with nearly a half million people which is hardly a "stream of small communities". And it has 40 AM, FM, higher power translators and LPFMs.
After that, you are in the Riverside / San Bernardino market, a metro of 2.5 million and the 26th largest metro in the US.
So the only small communities between the outskirts of Phoenix and the large Palm Springs metro are Quartzite and Blythe with Brenda, population about 500, the next largest. That's a pretty good description of "desolate". What I don't see is any "solid stream" of communities save an occasional gas station with a couple of mobile homes.
however, there are also some big hills which can and do affect radio signals - a problem even in metro L.A. itself.
Not really. Except for the part of the LA market behind the mountains (Lancaster / Palmdale) and deepest part of Orange County (San Clemente and south) the Mt Wilson Class B stations cover the whole market quite well.
Just like Phoenix, there are some FMs that are rimshots or low power Class A facilities that don't cover the market well, but the hills, save for the Santa Monica Mountains, don't cause significant issues inside the LA Metro. Sa,e scenario for AM. Just as in Phoenix, there are only a couple of full signal stations in the market.
After reading your comments, I really have to think that you had either a broken antenna connection or a really horrible radio as signal issues are not a problem for the significant stations in LA, either AM or FM.
I have been driving that route since the 60's and it used to be that you could tune in (mostly AM) stations almost continuously from the outskirts of Phoenix all the way to the ocean. Not any longer. That was my point.
I have been driving it since the early 70's when I lived in Phoenix and worked at KWKW in LA; I notice no difference in the AM station coverage while FM coverage has improved as nearly all stations along the way have upgraded facilities as FM grew in importance. Again, I think you had a stinky radio.[/SIZE][/FONT]