That antenna location is still far South of that large hill in the South part of Austin.
But the tower is 1257' high and the antenna is at about 2000 feet above sea level. The objective is not to just cover the city of Austin but all the folks in Bastrop, Caldwell, Hays, Travis and Williamson counties who are, every one of them, in the Austin radio market (Metro Survey Area) and have an equal and proportional chance of being in the ratings sample.
Over 50% of the market population of the Austin MSA is not in the city of Austin.
Between Oltorf and Riverside is an elevation change of several hundred feet - I lived there for a year and a half.
However, the center of the city is at less than 500' AMSL. The tower and elevation of the site are actually quite useful for covering all of Travis County and all the metro except extreme northern Williamson, which is of a low population density.
There are parts of Austin where I don't get KBPA as well as I used to in Cypress. Especially when I go up to Cedar Park, down to Lake Travis, etc. That real estimation of their coverage is going to be interesting, but not nearly as interesting as looking at 101.1 in the Austin area!
It has a good enough signal to be, based on the average of Jan to March books, the #1 25-54 station in the market. It's cume is, on average, fully 30% of the entire 12+ population of the market and 33.5% of the 25-54 population.
Any hilly metro will have some shadows, holes and the like. KBPA is proven to have a signal good enough for it to be #1.
Back to the subject of fringe ratings. Houston, you got a problem. The Woodlands and Conroe. Populations booming, population density heading in the worst possible direction for the Senior road installation.
It's a 2000' tower holding full C's. The 60 dbu extends to the far top of Montgomery County. Harris County has 9 times the population of Montgomery County, and most of the Montgomery population is in the southern quarter of the county anyway.
By the time the population far into Montgomery becomes an issue, we won't be using AM or FM to reach listeners anyway.
What makes sense for hip-hop reaching the early wards won't make sense for country or top-40 because their listeners aren't in those wards. Their listeners are in Katy, Cypress, Spring, the Woodlands, Conroe, etc.
You make the mistake of thinking that hip hop listeners are only in low income neighborhoods. That is just not correct. Neither is the assumption that country listeners only like out in the rural parts of a metro.