ARLA/CLUSTER: Novo decodificador para RTTY.

[João Costa > CT1FBF]

*GRITTY 1.2*

RTTY decoder for Windows XP/7/8, 32/64-bit

*FREEWARE*



GRITTY is an RTTY decoding program based on the technology developed for
the RTTY Skimmer Server <http://www.dxatlas.com/RttySkimServ> project. This
is not a skimmer, it decodes a single signal in the 3-kHz audio coming from
the transceiver via a soundcard, just like any other RTTY program.





*Fig.1. GRITTY is decoding weak signals. Unreliable characters in the text
are printed using light colors, many of them are errors, but the program
still determines the correct callsign and shows it on the callsign stack.*




How It WorksThe decoding algorithm in GRITTY is based on the methods of
Bayesian statistics. This results in a better decoding accuracy than other
algorithms, created by the trial and error method, typically achieve. In
the Bayesian framework, all information is represented in the form of
probabilities. In particular, the Bayesian decoder computes not only the
5-bit Baudot codes, but also the probability of error in each of the bits.

One obvious use of these extra data is to compute the error probability for
each character in the text, and color-highlight the unreliable characters.
Another use is smart squelching. In GRITTY, the squelch function is based
not on the signal amplitude but on the error probability. This works better
than the traditional squelch since it allows decoding of very weak signals
but suppresses strong signals when interference makes accurate decoding
impossible. The net result is very little garbage in the output.

The bit error probabilities are also used in other, more interesting ways.
GRITTY not simply prints what was decoded, but performs some intelligent
analysis of the decoded text. When similar callsigns appear in the message,
an experienced operator can often tell which call is correct and which one
is corrupted. GRITTY can do the same, but more accurately than a human,
because it can compare the calls bit by bit and merge the probabilities
using the Bayes formula. Quite often the program is able to determine the
correct callsign and put it on the call stack even if all received copies
of the call are corrupt.

A similar approach is used to find and correct the errors in other parts of
the text, such as exchange numbers and CQ/DE keywords, to fix incorrect
shift state, etc.





Copyright © 1998-2015 Afreet Software, Inc.

Em 29 de abril de 2015 12:43, João Costa > CT1FBF <ct1fbf  gmail.com>
escreveu:

> Olá pessoal,
>
>  O GRITTY é muito superior ao decodificador do DM780. Nos testes que
> eu fiz, decodificou sinais que o DM780 não conseguiu.
>
>  Eu pretendo usá-lo em conjunção com o DM780, assim eu consigo usar
> todas as facilidades da suíte Ham Radio Deluxe.
>
>
> Forte 73,
>
>  André - PY3IT
>
> **************************
>
> Bom ver que outros colegas estão confirmando as minhas primeiras
> impressões sobre o GRITTY.
>
> Quando comparei a GRITTY com o FLDIGI, a diferenca foi tão grande que
> achei suspeito. Vou comparar com o Airlink Express também, para ver o
> que acontece.
>
> Alguém já integrou com outros programas?
>
> 73 de Vince, VA3VF
>
>
> Fonte: Araucaria mailing list
>
>
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>
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