Red Wave Radio

I found this one channel on 454.300MHz. Day and night I always have an
image(my scanner stops), but its just a high pitched whistle. Every 10
seconds or so I hear digital beeping and buzzing and static then back
to the whistleeeee.
What is this?

Also, how come sometimes in the fire dispatch channels around 46.00 I
hear strange humming which even if I turn squelch to the highest it
can go, the humming is still there.

And what are thoes horizontal antennas on fire and EMS building? I see
them sometimes on towers too. The radiating little antennas are
sticking up and down and the actual poll is supported on its side (u
get the picture)

Thanks
Dave