Tecsun PL-368 Manual page 29

These forms of amplitude modulation, which cannot be demodulated by
the envelope detector, arise from fairly common situations. Although the
broadcast signal is transmitted as a conventional double-sideband AM
wave, the detuning and skywave reflection of the radio will change this
AM signal into one or a combination of the forms shown in the chart.
When there is adjacent channel interference, TV horizontal scanning
harmonics, interference of the carrier frequency and the like, then using
the upper sideband or lower sideband to receive the unaffected sideband
can significantly reduce the interference. This is because these types of
interference usually only affect one sideband of the AM signal, and the
content of AM radio broadcasts exists in two sidebands, in which each
sideband contains the same content.
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