On Feb 22, 10:58 am, "Richard Fry" wrote:
An estimate is possible, but assumptions will need to be made. If you can
post the readings you got, the path lengths, and the general location for
the transmit site I can give you some idea about that.

Of course if you can post the call letters of the station then the FCC data
for that station will show they should be.

The readings that I got were 3.1 mV/m at 15 meters away. 1 mV/m at
0.32 km away. Finally, 0.71 mV/m at 0.80 km away. We traveled a
straight path that was parallel to the direction of the antenna. It's
not an FCC station, but my professor got permission to test it briefly
at 1.79MHz. I don't know the exact area that we were located, but it
is somewhere east of Magdalena, NM.

The FCC publishes charts that may be used for this purpose. As for minimum
usable daytime field for a typical, cheap indoor receiver in an urban,
residential area, a value of 1 or 2 mV/m typically is needed.

RF http://rfry.org

Thanks! I was curious about AM stations at one time and looked up some
FCC data. I noticed that some stations have lower power output during
night time compared to daytime. For example, one station had 1 kW
during daytime and decreased it to 300W (I think) during night time.
Does that indicate that night time propagation is better?