>Something I've always wondered about regarding harmonics: If a
>harmonic was generated locally by rectification, wouldn't the
>sidebands be harmonics too?
Let's assume that the station at 880 is only transmitting a single 1 KHz
tone. The transmitted AM signal would consist of the carrier at 880 KHz
and two sidebands one at 879 KHz and the other at 881 KHz. Assuming again
that the transmitter output filtering has been compromised or removed for
some reason, then the 2nd harmonic components would be 1758, 1760 and 1762
KHz. For the 4th harmonic, the components would be 14064, 14080, and 14096
KHz.
If the station now transmits a typical audio signal (+ or - 10 KHz and all
the audio frequencies in between!) then the signal components would be
spread out and the result would sound more like power line noise than
anything else.
Harmonics can also be generated outside the transmitter, as Wiley
suggested, by the rectification of the main signal in the vicinity of the
transmitting antenna. This could be, for example, a faulty insulator
allowing a (poor) contact between two conductors.
If the receiver is located very close to the transmitter, then this
rectification could actually be occurring at the receiver due to
overloading of the front end.
-Zyg-
AF4MP
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