Back n the day WNBC 66 AM in NY was the biggest thing around.you wouldn't have really heard about FM at all.
I accept the premise that FM was doing more of an AOR format back then.which would have been high school and college age listening.Jethro Tull.GenesisBTOetc.progressive stuff.But WKRP was timed perfectly in that the world was changing and AM/FM was becoming equally acceptable.
so depending on the market and the year the biggest station could have been am AM or an FM

Yes, the cheap Ford Pinto I drove in my pizza delivery job in high school (1978-79) only had AM.
My mom had an AM-FM in her late 70s Plymouth, but FM was mono.
My own used car in high school, an AMC Hornet, was AM only.
I purchased an AM=FM cassette stereo which I mounted on the bottom of my dash board, just above the carpet floor (screwed into that part of the car).

Speaking of cars, many of them didn't even come with a radio. It was an optional feature back then.

Like that was the click - whhrrrr - click worst part of an 8-track tape.

8-tracks were a continuous spool of tape usually with an entire album on it. I never cared for this format because you could not rewind it. For more information, see Wikipedia. They go into detail and show diagrams of how it works.
"I will not go down in history as the greatest mass-murderer since Adolf Hitler!" - Merkin Muffley

Ok, tell me a little about 8-tracks. I remember seeing them in older cars growing up, but never actually used one or saw them used.

I lived all around the country in the 70's and in many areas the best music stations were on the AM band. Now ask about 8-tracks.
Three things cannot be long hidden: the sun, the moon, and the truth.

lol. Yes, young one, AM radio ruled the air until the mid 70s. Cars didn't even come with an FM band. So WKRP, in '78, would have been one of the last AM rock stations.

In the mid-1980s, WLS was a combo of music and talk.
It was music until later in the evening, say around 9 p.m., when the station aired local talk programs like advice shows.
I vividly recall hearing the station play Toto or other artists in the evening and then moving to talk.
Later, like most other prominent AM stations, it went totally talk.

Did any other "WKRP In Cincinnati" cast members work in radio?

I grew up near Decatur, IL, and if you wanted rock, you listened to WDZ AM (though it changed formats once or twice) or tuned in WLS, from Chicago (which could be heard across most of the state). My mother had an FM-capable clock radio and the station played easy listening, with stuff like Ray Coniff, Andy Williams, the Carpenters, and the like. It would be a few years before Y103 (the FM version of WSOY AM radio) would switch to rock.
The ironic thing is that Gordon Jump was once a DJ in Decatur (I believe it was at WDZ).
Fortunately, Ah keep mah feathers numbered for just such an emergency!

Back in the day ALL cars came with only AM radios. That didn't change until the mid 70s.

Back in the day some cars had only AM radio. My father drove a Plymouth with an AM only radio. - jefgg
My first car, which I got in 1980, was a 1973 Chevy Malibu with the old factory-installed AC Delco AM-only radio. The previous owner had added an 8-track player. I put in a couple of rear speakers but I never did get around to installing an AM-FM stereo before I got rid of it. Those were the days.
"If life's for living, what's living for?" - Ray Davies

Back in the day some cars had only AM radio. My father drove a Plymouth with an AM only radio.

It was pretty much the same for me. I remember my older brother listening to a New York FM station, and liking the music, so that was what I listened to. I never listened to AM radio unless it was in someone's car, usually an older person (parent, etc) who just wanted to hear the news, oldies, etc.

I was ten years old when WKRP began in 1978. I had assumed it was an FM station. I grew up listening to New York radio stations. By 1978 rock and roll was played on FM radio. AM radio was for pop music, talk, news and ethnic programming. Maybe it was different in other markets.

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In the 1970's, AM radio stations played mostly a top 40 format which was pretty crappy music by the late 1970's. You could also find "easy listening" stations which basically played elevator music. I think WKRP was basically this format before Travis changed it to R&R. You could also find stations that played "big band era" type music from the 40's-mid 50's.
The rock station featured in WKRP was really more like a F.M. station of the time period. The format was called "AOR" or Album Oriented Rock. Basically DJ's would play a wide assortment of songs from rock bands not just the hits. You would also find Jazz & R&B stations on F.M. You could also find "Oldies" stations that played music from the mid50's early 60's, basically pre Beatles Rock and Roll.
F.M. radios were kind of expensive in the 1970's and you could rarely find a F.M. radio in a car. Also the F.M. signals back then were kind of weak so the reception wasn't always great.
Around the early to mid 80's as the availability and technology got better, you started seeing more F.M radios. The top 40 format switched to FM stations and rock AOR stations slowly devolved into what's now called "classic rock". Classic Rock basically plays greatest hits packages from the big groups of the mid 60's to early 80's.
Because AM stations were now available and rather cheap, the mid-late 80's saw the rise of Right Wing talk shows and all sports formats.

Thanks. l guess it doesn't really matter whether the stations was AM or FM at this point or any point, for that matter, especially if the writers sent mixed signals (so to speak).

I wonder if any of the dialogue referred to whether this was an AM or FM station?
When Herb started his sales pitch to Del he said something like, "Let's tune to WKRP AM radio where your advertising dollar works it's hardest."

Very observant! Good points about the wattage. The map points to WKRP as being an AM station, though the pilot contradicts that.
I wonder if any of the dialogue referred to whether this was an AM or FM station?

If you look at the map in the lobby, 'KRP was a 5000 watt station (although it was a 50,000 watt station in the pilot)and those are AM numbers.

Generally speaking, until the early '80s most AM rock stations were "top 40" and most FM rock stations were AOR, album-oriented rock. WKRP strikes me more as AOR, and the DJs are usually playing albums, not singles, so it would more than likely be on the FM dial. On the other hand, the radio contests that WKRP had also seemed more in keeping with AM stations at the time.

There's still music on AM today.
I don't even own an Ipod.