Why do "news" radio stations broadcast on AM frequencies instead of FM frequancies?

Question

Considering that the sound quality is worse and that the signal gets interrupted when driving under a bridge or inside a tunnel, why do news stations broadcast on AM radio instead of FM radio?

Answer 1

The sound quality is exactly the reason.  Stations were originally on the medium-wave AM frequencies (between 550 and 1350kHz), which was later expanded to include 550-1710kHz.  The occupiable bandwidth for each station is minimal when compared to that given to FM stations (+/- 5kHz versus +/- 100kHz).  Because of this, the stations who moved to FM to take advantage of the higher fidelity possible were the music stations.  The news stations didn't need the higher fidelity, so remained on their existing licenses, since moving would be very costly.

Answer 2

All signals are interrupted by tunnels.  

Some bridges do interrupt AM signals due to their longer wavelengths not making it through sub-wavelength sized lattice of girders, whereas FM signals with their much shorter wavelengths get through without being attenuated.  

AM transmitters are cheaper than FM, and AM stations are allowed to transmit more power, extending their reach.   Also, the longer wavelengths of AM are less impeded by the curvature of the Earth then FM signals, which tend to be line-of-sight (unless there's a big building for them to reflect off).

Answer 3

Because as music radio stations made the move from Am to Fm in the 1980s, they needed a format to fill stations that were now shells of them former self (Most news-talkers on AM were former Top 40 outlets in the 1960s and 1970s)... Enter talk radio.  Talk radio doesn't need hi-fidelity like say a music station would hince it's a format that has saved many Am stations.

Fm talk is slowly becoming a force on FM, But I don't think you'll see it a dominant force for a while. For example, I live in a market where there is a AM talker on a full power FM station. The AM half still ranks 3 to 1 over the FM and both basically carry the same thing (there is one program not allowed to air on the FM)

But with Fm talk having to compete against music stations instead of owning the band it's on.. I won't expect to see it in most markets anytime soon