The picture of "noise" tells us nothing - other than 10khz is down 30db
from carrier. Were it relative to something - that would tell us much.
As it is - it just shows an unknown spectrum of ???? Put a reference in
there (or a known weighted/gated noise source such as specified by NRSC
- like a BruelKjar or equiv.) THEN you can make some solid deductions.


That spectrum was taken during a quiet piano passage with background
noise. The piano, played softly, had little treble, so the spectrum
above about 3 kHz is the product of the program noise spectrum, and
the spectral response of the station, which includes playback
electronics, processor, transmitter, and antenna. The dominant
spectral feature of the station's frequency response is the processor
preemphasis. If the noise spectrum is flat, what you see in the screen
shot is the preemphasis curve. Its absolute level reflects the level
of the background noise, which isn't relevant. But the shape is. The
curve shown is typical of the spectral response you'd expect to see
for a preemphasized AM transmitter. The key point is that it stops
suddenly at 10 kHz, not somewhere below. All of the spectra I've shown
do the same. (The spectra of the two Mexican signals stop at 8 kHz.)

Here's a final screen shot: http://n2.net/k6sti/am1210.jpg . This is
nearby station at 1210 kHz that was broadcasting a live announcer from
a local studio at the time I recorded the spectrum. The carrier is at
the left edge of the screen, the center of the screen is 1220 kHz, and
the horizontal scale is 2 kHz/div. This image shows the upper sideband
in some detail.

If you were designing a high-performance AM receiver, what IF passband
would you use to fully recover the modulation from this signal?

Brian