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[aprssig] I'm brainstorming, so don't beat me up!

scott at opentrac.org scott at opentrac.org
Fri Jul 8 02:37:22 UTC 2005


Is that really suitable for FM?  I'd think it'd be more appropriate for SSB.

I'd really like to see how 4800 bps GMSK compares to 1200 and 9600.  I think
it might work better with voice radios, with plenty of bandwidth for APRS.
Yeah, there's not much out there that supports it... But I'm working on
that.

Scott
N1VG 

> -----Original Message-----
> From: aprssig-bounces at lists.tapr.org 
> [mailto:aprssig-bounces at lists.tapr.org] On Behalf Of Wes Johnston
> Sent: Thursday, July 07, 2005 6:39 PM
> To: TAPR APRS Mailing List
> Subject: Re: [aprssig] I'm brainstorming, so don't beat me up!
> 
> What about q15x25? mix32 (or is it mix-w) supports it... 
> agwpe is supposed to Real Soon Now. q15x25 is 15 PSK carriers 
> with an aggregate bit rate of 2500 baud on normal channels, 
> and FEC. It's just a tweak processor intensive to encode and decode.
> 
> Wes
> 
> 
> Gerry Creager wrote:
> 
> > Actually, the 2-tone modem history pertains to telephone line 
> > optimization for tone detection.  Preemphasis and deemphasis were 
> > rampant, and tone detection was done with LC lumped 
> constant filters.
> > A single tone detector had a higher error rate.  Once you 
> get to two 
> > tone systems (remember RTTY?) one can start thinking about 
> different 
> > encoding and modulation schemes.  When one is thinking in terms of 
> > bits/transition, multiple tones or constellations thereof 
> start making 
> > sense.
> >
> > I suspect we could create a high performance CW system 
> using DSPs but 
> > we're talking now about transitions per bit rather than bits per 
> > transition.  For what we're talking about, does it make sense?
> >
> > gerry
> >
> >
> > Curt, WE7U wrote:
> >
> >> On Thu, 7 Jul 2005, Earl Needham wrote:
> >>
> >>
> >>> At 10:40 AM 7/7/2005, Curt, WE7U wrote:
> >>>
> >>>> While we're at it, would some other non-standard rate _between_ 
> >>>> 4800 and 9600 work?  What is the maximum rate we could 
> get through 
> >>>> voice-grade rigs without modification, even if we have 
> to change to 
> >>>> a different type of modulation?
> >>>
> >>>
> >>>         If we're going to consider another form of 
> modulation, I'd 
> >>> like to enter my vote for 100 WPM (or faster) CW.  Maybe a LOT 
> >>> faster -- can we design a system that does 1200 WPM CW?
> >>
> >>
> >>
> >> That's extremely fast!  What you're describing is (assuming 5-char 
> >> words and a space between each one) 6 * 1200 chars per second, or 6
> >> * 1200 * 8 bits per second.
> >>
> >> I assume you mean something equivalent to 1200 baud packet 
> speed in 
> >> terms of characters transferred.  That's 1200 bits per second.
> >>
> >> I don't know whether a CW system could be designed that 
> would compete 
> >> with 1200 baud AX.25 packet.  There must be a good reason 
> that people 
> >> went with the 2-tone modem originally.  Perhaps coherent CW would 
> >> suffice for this idea, which I think is a two-tone modem 
> anyway isn't 
> >> it?
> >>
> >> -- 
> >> Curt, WE7U.   APRS Client Comparisons: 
> http://www.eskimo.com/~archer
> >> "Lotto:    A tax on people who are bad at math." -- unknown
> >> "Windows:  Microsoft's tax on computer illiterates." -- WE7U "The 
> >> world DOES revolve around me:  I picked the coordinate system!"
> >>
> >> _______________________________________________
> >> aprssig mailing list
> >> aprssig at lists.tapr.org
> >> https://lists.tapr.org/cgi-bin/mailman/listinfo/aprssig
> >
> >
> 
> 
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