Your example is not a measure of a an amplifier but a system that has other
frequency determining components.
You also are mixing or combining the products of RF IF and AF in the
receiver. But a simple non-frequency dependent (no filters affecting
sidebands) non-linearity will always produce equal products above and below
the test signals. As I said, that is why they test amplifiers with RF
two-tone generators.
73
Bill wa4lav
At 10:28 PM 3/6/2003 -0500, Tom Rauch wrote:
>There sure is a difference! I have to be very careful doing two-tone
>receiver tests to make sure the levels are equal, otherwise one 3rd order
>product will be much stronger than the other.
>
>The stronger signal generally becomes the local oscillator and is more
>limited (gain compression), while the other is a linear product of the
>mixing. So 2f1-f2 is not the same level as 2f2-f1 when either F2 or F1 is
>stronger.
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