The article stated that
> the self supporting towers will be replaced with guy
> supported towers and it is projected to be completed in the
> spring.
>
> The article also said this was being done to improve the
> stations capability to do HD broadcasting. Please explain
> why the type of tower would have anything to do with HD
> broadcasts.
>
I can't comment entirely intelligently without knowing a lot more specifics on the towers, but yes, HD radio on the AM band does require a much more perfectly planned, tuned and matched antenna system. The design of the tower array effects the Q of the antenna circuit, the linearity across the passband, and ultimately its ability to carry the much more intricate waveform for analog and digital combined. If the Q of the old tower was very narrow, then they would more certainly want to replace this for IBOC.
The characteristic impedance of the tower at the carrier frequency, the resistance and reactance of the tower, and whether or not it is grounded or isolated all effects this. (The FCC no longer licenses grounded AM towers for directional stations because of the problems with nighttime take-off angles with slant-wire fed radiators, so that's kind of academic.) With IBOC on AM, 50j0 needs to REALLY be 50j0.
So while it seems a bit odd on the surface, it's not BS.
--Paul