Nathan Obral said:
It also works the other way around.
Seattle (KIRO) Indianapolis (WIBC) and Phoenix (KTAR) are perfect examples of an established AM talk format moving to the FM dial, which clears the way for the low-overhead sports formats to take over on the AM signal. It doesn't hurt that all three of these AM sports stations also have a good dose of play-by-play; KIRO has the Mariners, WFNI - the former WIBC - has the Colts, and KTAR has the Diamondbacks and Cardinals.
KIRO 710 is directional but looks like it covers most of the Seattle metro fairly well at night. But 710 is a mess (LA, Amarillo, KC, Bismarck, & Denver have to be protected) at night.
WFNI has horrid-to-nonexistant coverage at night in the many parts of the Indy metro, with their 10 kW nighttime signal shoehorned in (and it's been that way for close to 50 years). They have to protect many other stations, including KNX, hence the highly directional (to the SW from near Lebanon) signal at night.
KTAR runs only 5 kW, and gets weak 30-40 miles away from its transmitter on the near-NE side of the city. Trouble is, the Phoenix metro is about a 50 mile radius from downtown. I don't think they can get a power increase, not only because they have to protect stations in Portland, Dallas, & Fresno, but they would probably have to move their towers out of the city. They're literally in the middle of a shopping mall parking lot - the towers were there first, built in 1941 when the area was farmland.
Also, the Cards' flagship is KTAR-FM 92.3, not 620. They only put those games on the AM when there is no conflict with the D'backs, Suns, or ASU.
As for 1250/Pittsburgh... who in the hell would want that station now?
That's the kind of marginal station I was talking about: A 5 kW station that doesn't cover the entire Pittsburgh metro overly well at night, although city coverage looks OK per Radio-Locator.com.