National messaging system

[Curt, WE7U]

On Tue, 18 Jan 2005 dubose at texas.net wrote:

>    Pactor III is 2.4 KHz wide and has a thoughtput of close to 200 WPM at a
>    -5dB SNR on a poor CCIR channel.
>
>    MT63 has a 2 KHz mode that provides 200 WPM throughput and will provide
>    this throughput down at -5dB SNR on a poor CCIR channel.
>
>    Rick's, KN6KB, SCAMP is about 2.4 KHz wide (maybe 2.7) and has a
>    throughput averaged multi-path poor CCIR channel and -5dB SNR about the
>    same as PIII
>
>    The advantage of MT63 is it runs on a soundcard not proprietary hardware.

And it's slightly narrower than the other two mentioned.  I see why
you were focusing on that protocol as a possibility for a more open
system.  That plus the fact that it can run from a soundcard.


>    Sure a lot of Pactor III and MT63 2 KHz signals on 30M is going to crowd
>    the band...but I've never heard 30M crowded.  I may just have missed the
>    pileups. Hi Hi.
>
>
> Isn't it comparing apples and oranges between the narrow and the
> wideband signals?
>
>       Sure, but Pactor III, SCAMP and MT63 are  all wideband
>       signals...between 2 and 3 KHz.
>
> It seemed from earlier discussions that Pactor-III was going to have
> limited uses except perhaps in emergency situations where of course
> they could take priority on the bands (where the emissions are
> authorized) to get traffic through.

I recall some earlier discussions somewhere that talked about
Pactor-III being too wide from some band segment or other.  I guess
I was under the impression that it was wider than what you specified
above.  My mistake.  It's similar to a SSB signal in bandwidth.  Not
all that wide.


>    I think that the WinLink folks and the ARRL expect it to be running all
>    the time.  The limiting factor is that Pactor II and III require an
>    expensive controller and Pactor I doesn't...that is if the KAM controller
>    isn't considered expensive.  Pactor I can also be run using a PK-323 that
>    has been upgraded.

Pactor-I can also be run with the "hfmodem" driver in Linux and a
soundcard, the ultimate in cheapness.  Has anyone on the list done
so and compared the performance to Pactor-I via a TNC?


> If we can use narrow signals or perhaps multiple narrow signals we
> might be able to use the system much more, on more bands (frequency
> agile depending on MUF and distance of QSO), and get more practice
> during non-emergency times with the system.
>
>    Maybe but right now the the wider the bandwidth the more data you can
>    push though.  If you have several narrow signals, you will have overhead
>    with each one so put the overhead on just one signal.

--
Curt, WE7U.   APRS Client Comparisons: http://www.eskimo.com/~archer
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