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[aprssig] APRS Bandwidth

Steve Noskowicz noskosteve at yahoo.com
Wed Jun 24 01:23:32 UTC 2009

--- Curt, WE7U wrote:
>   http://www-personal.engin.umd.umich.edu/~richarpc/ch2_5_modems.ppt
> -- Curt, WE7U.       

This PPT completely looses me with his subscripts, HOWEVER.

Simply looking at his spectrum it is clear. Considering the two "carriers" as being amplitude modulated by the Baud "square wave".  Then, only take the first bair of AM sidebands (band limit the square wave).  You get the bandwidth is the shift plus the "modulation frequency" on the high side (upper sideband) plus another on the low side (lower sideband) for  Bw = Shift + 2 * Fmod.  The ignored sidebands are between the two carriers.

Shift = 200
Fmod = 150

Still gets 500 Hz.

73, Steve, K9DCI


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