[aprssig] I'm brainstorming, so don't beat me up!
Wes Johnston
aprs at kd4rdb.com
Thu Jul 7 21:39:26 EDT 2005
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!"
>>
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>
>
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