The problem is that the "smearing" is additive.  The transmitter 
adds some, the ionsphere adds more, then the receiver even more.  In 
order to maximize the phase coherence, the ionsphere should be the 
only contributor.  I recognize that economic costs may impact this.  
But again, I just wanted to point out that dealing with the computer 
side, i.e. modem, is only one part of the system.   
 
--- In digitalradio@yahoogroups.com, KV9U <[EMAIL PROTECTED]> wrote: 
> 
However, I think that the ionosphere is  
> even worse than most amateur equipment. 
>  
> Here is a URL that helps explain it: 
>  
> http://www.rfengineer.cc/pdf/group_delay.pdf 
>  
> 73, 
>  
> Rick, KV9U 
>  
>  
> DuBose Walt Civ AETC CONS/LGCA wrote: 
>  
> >Rick, 
> > 
> >Please explain "group delays".  I am unfamilar with that term in 
reference to transmitting equipment. 
> > 
> >Walt/K5YFW 
> > 
> >-----Original Message----- 
> >From: digitalradio@yahoogroups.com 
[mailto:[EMAIL PROTECTED] 
> >Sent: Wednesday, September 20, 2006 4:28 PM 
> > 
> >[stuff deleted] 
> > 
> >Another thing that I came across in my web searching was that 
amateur  
> >equipment generally has group delays that make it difficult to 
even  
> >employ some of the modems we have been discussing. 
> > 
> >I wonder if any of the modem experts might comment on that. 
> > 
> >73, 
> > 
> >Rick, KV9U 
> > 
> > 
> >   
> > 
> 
 





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