Whence the nighttime interference on 1030?

[Doug Drown]

I live on the upper midcoast of Maine, where WBZ's daytime signal comes in
like gang busters --- absolutely crystal clear, no hiss or interference, as
though the transmitter were just down the road.  One the sun sets, however,
it deteriorates rapidly, especially at this time of year.  What is/are the
station(s) I'm hearing on 1030 kHz?  They seem to interfere with one
another, such that I can't make anything out plainly.  Am I correct in
thinking that 'BZ's signal is nondirectional?  If so, the presence of these
other stations' signals surprises me.