Wait wait wait, I always suspected KRP was a subversive hint at "Crap" but how does this address the question? Why is Cincinnati more KRPy than St. Louis or Pittsburgh or KC or Atlanta for that matter? Did Wilson have a bad experience with Cincinnati, or was there a specific reason for him picking it?
I think that phonetically WKRP simply sounded better with Cincinnati than say, Albuquerque which has the same number of syllables.
"It's a real burden being right so often." Captain Malcolm Reynolds, Firefly

how does this address the question?
The geographical area (of Cincinnati) corresponds with the (then at least) fictitious call letters. American broadcasters can't or couldn't choose any random set of letters since sometime between the World Wars. The W or K was based on east or west side of the country and there was a specified list of available choices for the 2nd thru 4th letters assigned by state/region on a next available letter basis. You can find a detailed wiki about it if you do a search.
There were and still are exceptions to all this but it's the common reasoning. They certainly could have gotten away with any of the cities you mentioned too - after all it was just a fictional comedy. In that case people would now likely be pointing out various errors based on the historical naming convention and so on.
Eeek!!! I'm getting dressed.

Wait wait wait, I always suspected KRP was a subversive hint at "Crap" but how does this address the question? Why is Cincinnati more KRPy than St. Louis or Pittsburgh or KC or Atlanta for that matter? Did Wilson have a bad experience with Cincinnati, or was there a specific reason for him picking it?

Why was the show based in Cincinnati?
According to show creator Hugh Wilson:
Wilson created "WKRP" from his days as an Atlanta advertising executive, when he listened to Atlanta radio stations. He had never been to Cincinnati, but picked this city as the setting because it went with "WKRP," the call letters he chose because they stood for "crap." ~ John Kiesewetter, jkiesewetter@enquirer.com
This agrees with research I did earlier that suggested the call letters led to the choice of city, at least roughly. Once he picked the name of the fictitious station, it narrowed his choices down to that geographical area and
WKRP in Dayton
just didn't sound right I suppose. All of the guesses of which particular old AM station in Cincinnati the show was based on are wrong. It was just inspired by Wilson's time in the Atlanta area listening to radio. The real life basis for
Johnny Fever
worked morning drive in the Atlanta market, though he may have once worked in Ohio too.
Eeek!!! I'm getting dressed.

Expect everything to be based in L.A.?

You are right. A lot was ran through Cleveland (grow up in the area). But I think Cleveland would have been too large for a the show's premise. We would drive to Cincinnati for concerts, though. So, it was still close enough to the hub of the pulse of R-N-R, but far enough away to be it's own entity. It's large enough to draw crowds, but small enough for no professional DJ trying to strike it big to want to end up there.
How can you expect your life to change if you don't change?

Dr. Johnny Fever was based on the late "Skinny" Bobby Harper. He was a DJ who worked at Cincinnati Top 40 station WSAI AM before moving to 11 other stations.
I heard that large and/or blue collar Midwestern cities were strong markets for rock and roll music.

Why not? Where did you want it-NYC?

Well, it wasn't really the early days of FM. It had been around since after WWII, and we had an FM radio in the early 1960s.
For most Americans, the 70s were the early days of FM radio, particularly the early 70s.
AM radio was still king of Top 40 music until the mid-late 70s.
KIMN-AM was a Top Denver top-40 station through the mid-70s. I recall my older cousins having it on in their car back then.
Most car radios were AM-only until the late 70s and those that were AM-FM had FM mono only, at least on my mom's Plymouth then.
Yes, FM radio had been invented after WWII, but there were few (if any) FM stations. So no one owned FM receivers.
Why would one buy an FM receiver if there weren't any stations broadcasting on the band?
In a late
Leave It To Beaver
episode (1963),
Eddie Haskell
tells Wally he has an FM radio in his car, but it's staticy and the only station on it plays classical music.
Like
COLOR TV,
sure, it was "around" but again, few (if any) TV stations were broadcasting in color until the mid-1960s.
Though some programs were produced in color, it wasn't widely adapted.
Many people didn't get color TVs until the late 60s or early 70s when prices became more affordable.

When WKRP was on the air in 1978, I was 16. I had been listening to an FM, hard rock, album station for a few years at that point. I would safely say at least since 73, if not earlier. And it was well established when I started listening. I grew up in the Akron area listening to Cleveland radio. We were also not far from Cincinnati at all. There were a few AM stations still kicking' it. But they were typically only listened to by older people or younger and middle-aged people still listening to doo-wop music (Oldies). I am sure they existed, but I do not remember any "new" rock AM stations in the area. I don't think we could pick up Cincinnati radio, though.
In other words, you are correct. It was not a new radio format or frequency.
How can you expect your life to change if you don't change?

Well, it wasn't really the early days of FM. It had been around since after WWII, and we had an FM radio in the early 1960s. By the end of the 1970s, 50.1% of radio listeners were tuned to FM, ending AM's historical prevalence. By 1982, FM commanded 70% of the global audience and 84% among the 12-24-year-old demographic.
It is better to be kind than to be clever or good looking. Derek

I lived in northern KY and worked in downtown Cincinnati in those days and I always suspected that WKRP was based on the very real and wonderful Cincinnati station "102.7 WEBN" The station was total insanity in the 70s. It was the early days of FM and I had a converter attached to my '66 Charger so I could get the new FM stations.
http://en.wikipedia.org/wiki/WEBN

This message has been deleted.

Good question.

Why not Cincinnati?

I didn't say the city was in Northern Ohio. I said it was a Northern city in Ohio. Meaning a city in the Northern part of America.

It has very metropolitan-ness, but does have the farming and small town feel right outside it. It is a Northern city in Ohio with a Kentucky southern feel. So it will appeal to all American viewers.
Just FYI, Cincinnati is in Southern Ohio.

Both Gary Sandy and the late Gordon Jump are from Dayton.

It is a Northern city in Ohio
No, it is a Southern city in Ohio, probably the largest city north of Kentucky!
Cleveland, Canton, Akron and Toledo would be some of the best-known Northern
cities in Ohio. Then there's Dayton, my hometown, which is a mid-sized city
located between Columbus (Central Ohio) and Cincinnati.
Ignorance and apathy: I don't know
and I don't care.

It was also based partly a radio station movie named "FM" starring Martin Mull.
"'Extremely High Voltage.' Well, I don't need safety gloves, because I'm Homer SimpsonBNZsZsZsZsZsZsZ" - Frank Grimes

He didn't say middle OF America, now, did he?

Jay, you just showed your own ignorance. http://en.m.wikipedia.org/wiki/Middle_America_(United_States)

Middle America?
Have you seen a US map? Ever?

This message has been deleted.