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[hfsig] Performance of 24/192 soundcards? USB Soundcards

Lyle Johnson wa7gxd at fidalgo.net
Wed Sep 22 00:20:59 UTC 2004


> After a short search I could not find the G3RUH circuit 
> although I'm sure I've seen it before somewhere.

http://www.amsat.org/amsat-new/archive/index.php?t=./articles/James_Miller

You want the figures for, and the article, "9600 Baud Packet Radio Modem
Design"

> As I said, it's a modem implementation issue :-)
>
> > James is a very careful engineer, and he did some pretty extensive 
> > work with all this when he designed the modem and specified the 
> > required passband response.  The BER goes up pretty quickly 
> > as the LF response of the system degrades.
> 
> If he noted that the LF demands are increased compared to 
> plain old HDLC, why didn't he care to fix it?

He was making a modem compatible with the K9NG modem, so the scrambler
algorithm and its place in the grand scheme of things were already
constrained.

73,

Lyle KK7P






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