Flight crew described ATIS reception anomalies during arrival descent for MHT; listing ATIS reception range and frequency interference as the problem areas.

Narrative

This is more of an FYI of a condition that can be distracting during descents into MHT. MHT ATIS cannot be received until about 150 miles out even at the high flight levels. I could not receive it until after we had started our descent and were in the low FL300s. Usually at other airports this is not a problem but MHT has something restricting it; (terrain maybe?); that prohibits us from hearing it until close in. In addition there is an Approach Control that transmits on the same frequency. It sounded like Rochester Approach but I could not make it out. This makes it very difficult to understand the ATIS. If this Approach facility is busy it can make hearing the ATIS impossible. Its not until we get within 80 or so miles of MHT that the ATIS broadcast is clear and not interfered with. Two things. Change the frequency of the ATIS to eliminate the approach control transmission interference. Turn up the power of the ATIS transmitter or relocate the antenna to eliminate the interference or restriction to its reception. On the flight crew end; my solution is to just pull up the METAR in the ACARS and briefly listen for the ATIS code and active runway.