KellyClarksonTV said:
Recently my grandma (from Taiwan) gave me a radio that tunes into channels
in
the 70MHz-108MHz range, so I was playing around with the lower channels
most of
us are not familiar with, but I did happen to hear some familiar voices
from
regular (88-108) channels ... Do they broadcast to these stations, or
could it
be someone (perhaps a neighbor) rebroadcasted them for some reason? If
anyone
has a similar radio, please try it out yourself.
In the US, the FM band is sandwiched between TV channels 6 & 7. If you tune
down to the low end of the FM band, you'll hear channel 6 audio. If you have
a radio that allows you to keep tuning down, you should get a bunch of noise
that would be channel 6 video. Below that is channel 5 audio, followed by
channel 5 video. The range from 76 down to 72 MHz is fixed and mobile
communication, aeronautical radio navigation and radio astronomy. These
services might show up as noise (they're probably not broadcasting audio
signals). The mobile services are probably AM or narrow-band FM two-way
voice. The only thing that would sound like normal radio programming would
be the TV audio, AFAIK.
If you're hearing actual replicas of stations from the standard FM band,
it's possible that the radio is suffering from "images", the result of
front-end overload, or some other artifact of the frequency conversion
process that goes on in superhet radios. For example, the intermediate
frequency of most FM receivers is 10.7 MHz, so it's possible that a nearby
radio that was tuned in to a station in the standard band could re-radiate
(or fool your radio into receiving) the station on a frequency 10.7 MHz
below the regular assigned frequency.
Here's a chart showing the US radio spectrum allocation:
http://www.ntia.doc.gov/osmhome/allochrt.pdf