Re: Amplitude characteristic and harmonic spectrum

On Sep 25, 6:49 am, "pApAk" <n...@xxxxxxxxx> wrote:
What is the difference between these two terms:
amplitude characteristic and harmonic spectrum?

Some references (links, books) would be very, very helpful to me!

Thanks in advance!

While you can check anything from the ARRL Radio Amateurs Handbook to
the latest textbooks on electromagnetics and electrical engineering,
you will find the same general level informaton.

In modulation theory, no method of imposing information on a carrier
does no produce secondary frequency radiation. When you modulate a
carrier with information content, digital, music, or vido, the result
is a product that contains not only the fundamental carrier frequency
but in addition the product and difference frequencies. Any textbook
(take your pick) on modulation theory will tell you this. It's
somewhat related all modulators multiply the fundamental carier
frequencies and as a result produce the original carrier frequencies
plus sum and difference frequencies as well. Simply trig demonstartes
this. If you multiply A(sin) -- the modulation frequency -- with
B(sin) the carrier frequency, you get a produce with three compnents,
and these will not in the genral case be harmonically related.

Any simple spectrum analyzer will demonstrate this for you. Modulate a
1-Mhz carrier with a 440-Hz signal, and your spectrum analyzer will
display peaks centered on the carrier frequency, and at frequences 440-
Hz below 1-Mhz, and 44-Hz above. This is not exactly rocket science.

In the amplitude spectrum, more or less that same rules apply. If the
amplitude overloads the capacity of the amplifier, non-linear results
will be produces, and this is what we normally desicribe as
distortion, or in the extreme when diodes are employed to deliberately
induce this effect, is is or once what was called the "fuzzbox"
sound. Don't know about you, but I consider this sound offensive to
my ears! :-)

Hope this helps.

Harry C.







.

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