| Don Bowey 2007-07-05, 10:33 am |
| On 7/5/07 12:00 AM, in article 468c96c3$0$16567$4c3
68faf@roadrunner.com,
"Ron Baker, Pluralitas!" <this@aint.me> wrote:
>
> "Don Bowey" <dbowey@comcast.net> wrote in message
> news:C2B1DFAF. 6D6BD%dbowey@comcast
.net...
>
> Copying from my original post:
>
> Suppose you have a 1 MHz sine wave whose amplitude
> is multiplied by a 0.1 MHz sine wave.
> What would it look like on an oscilloscope?
> What would it look like on a spectrum analyzer?
>
> Then suppose you have a 1.1 MHz sine wave added
> to a 0.9 MHz sine wave.
> What would that look like on an oscilloscope?
> What would that look like on a spectrum analyzer?
>
>
>
So the first (1) is an AM question and the second (2) is a non-AM
question......
(1 A) On scope will be a classical envelope showing what appears to be the
carrier amplitude voltage varying from the effects of the sideband phases
and voltages. It's an optical delusion, but is good for viewing linearity
and % modulation.
(1 B) The spectrum analyzer will show a carrier at 1 MHz, a carrier at
999.9 kHz (LSB), and a carrier at 1.1 MHz (USB).
(1 C) Not asked, but needing an answer here, is "if the .1 MHZ modulation
were replaced by a changing signal such as speech or music what would the
analyzer show?" It would show an unchanging Carrier at 1 MHZ with frequency
and amplitude changing sidebands extending above and below the unchanging
carrier.
(2 A) The scope would display a 1.1 MHz sine wave and a .9 MHz sine wave.
They could be free-running or, depending on the scope features, either one
or both could be used to sync a/the trace(s).
(2 B) The spectrum analyzer will show a carrier at 1.1 MHz, and a carrier
at .9 MHz.
Don
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