There are only a limited number of AM frequencies available in the US, and
these frequencies are shared across the US. For example, a station in
Monroe, LA could be on the same frequency with a station in Las Vegas, NV.
This will work because the power of the stations is limited and they are
geographically separated.

But at night, an AM signal goes farther than it does in the daytime. It has
to do with skywaves vs. groundwaves, but I have long since forgotten that
stuff. So trust me, the signal goes farther at night than it does during the
daytime.

So, the stations must reduce power at night to avoid interference with other
stations on the same frequency. There used to be a type of station known as
a Class IV that was intended to basically serve a single community. They all
operated with 1,000 watts daytime and 250 watts at night. I think I worked
at three different stations that were on 1290.

It's basically the same situation with directional antennas; they are used
to avoid interference with other stations. But they also frequently had a
slightly different purpose; you could use a directional antenna to allow you
to put a station in a geographical location where it would not otherwise be
permitted.

If you're trying to find something to listen to on the ADF, you need to find
50,000 watt stations. Unfortunately, most of them are now talk stations. You
can probably google "50,000 watt radio stations" and find a list of them.

BTW: A lot of pilots used broadcast AM stations as an important part of
their navigation...


"Jonathan" wrote in message
news:ZmjRb.124495$sv6.673056@attbi_s52...
They have to switch to low power at night, and depending on which way
the antenna is pointing,

I always wondered about that. Why do they go to low power at night?
I have a local am station that I listen to on way home from work. Great
reception in summer (when i'm driving home in daylight). But bad this time
of year (drive home in dark)