In article .com,
bpnjensen wrote:
It's very important to point out that 2 different frequencies, when
mixed in a perfectly linear device, will not beat.

OK, I'll bite - why is this important in a world of radios that operate
on the heterodyne basis?

One important reason is that, in the real world, you can't have too much
gain in any one amplifier section, (in other words, on one frequency),
because the output of the amplifier can leak back to the input and the
circuit becomes an oscillator.

?And what makes a linear device different?
Are any commonly used radios linear devices?

The audio amplifier is designed to be a linear circuit. Another
word for heterodynes in an audio amplifier is "intermodulation
distortion".

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)