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Radio stations

  • Thread starter KellyClarksonTV
  • Start date
K

KellyClarksonTV

Jan 1, 1970
0
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.
 
K

Karl Uppiano

Jan 1, 1970
0
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
 
K

KellyClarksonTV

Jan 1, 1970
0
Thanks. I do hear channel 6 audio now. However, I'm also hearing 100.7FM in the
sub-88 range, far less than just 10.7MHz off. Any other explanation of this?
 
K

Karl Uppiano

Jan 1, 1970
0
KellyClarksonTV said:
Thanks. I do hear channel 6 audio now. However, I'm also hearing 100.7FM
in the
sub-88 range, far less than just 10.7MHz off. Any other explanation of
this?

Hmmm... 100.7 - 10.7 = 90, doesn't add up, however, 100.7 - (10.7 * 2) =
79.3, which might be in range. Also, not all receivers use a 10.7 MHz IF. I
might be grasping at straws here, though. If the experimental data doesn't
match the model, the model might be in error.
 
J

Joe

Jan 1, 1970
0
Another consideration is the calibration of your radio dial along with your
interpetation of the dial. Even an inexpensive radio with digital dials can
be off 0.2 or more.
 
K

KellyClarksonTV

Jan 1, 1970
0
Hey guys, you should really get a radio with 70-88MHz range ... there's two
X-rated stations in this range in our area ... for real ...
 
K

Karl Uppiano

Jan 1, 1970
0
KellyClarksonTV said:
Hey guys, you should really get a radio with 70-88MHz range ... there's
two
X-rated stations in this range in our area ... for real ...

OK, that would have to be the neighbor kid with a homebrew transmitter, but
why they would be broadcasting to basically no-one is beyond me. Besides, no
commercial station would risk their license like that.

Unless... Your area is not in the continental United States...
 
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