[Amps] IMD
Ron Youvan
ka4inm at tampabay.rr.com
Sun Jan 8 06:35:01 PST 2012
Gary Schafer wrote:
> Hi Bill,
> This is not a problem of not producing the square wave itself.
> A perfect square wave has all of the odd harmonics in phase.
> When you modulate an SSB transmitter with a square wave the phase of the
> fundamental and harmonics shift. This produces another fundamental that sums
> together.
This "different delay for different frequencies" is called "group delay."
It is something that messes up dial up modems. (so you don't get 56 kB/s)
> To pass an ideal square wave signal in an SSB transmitter requires infinite
> bandwidth and infinite amplitude. Though the square wave is not the ideal
> one it still requires a high amplitude capability.
> This is pointed out in the Collins "fundamentals of SSB".
> Here is a link to an article on the subject by Wes Stuart N7WS.
--
Ron KA4INM - Did you know ...
... that no-one ever reads these things?
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