"Robert11" wrote in message
...
Hello:

Was wondering about this:

When I tune to most any frequency with my scanner, the noise level is
really, really high when there is no
broadcast going on at that moment on that frequency.

When one does come on, it's as clear as a bell. This is true for the fm
as
well as
the AM channels.

Of course, the Squelch control pretty much takes care of the problem, but
was wondering if
this is "typical" ?

What is the source of the noise, possibly:

the radio itself ?
atmospherics ?

Or,... ?


The radio while operating FM is acting as a very high gain amplifier. It is
amplifing around one million or more times. Random electron movement in
conductors are generating enough noise to be heard . This is normal. It is
the property of FM to start quiting the noise as a RF signal is picked up.
AM has much of the same noise but most receivers have an automatic gain
control that cuts the gain of the amplifier somewhat. Lightning, some
motors with brushes, and many other devices make much of the noise you hear
on an AM receiver.