[RTTY] RttyCompare

[Jerry Flanders]

Way cool stuff. Thanks.

Maybe we can include some numbers in some of our discussions now.

Jerry W4UK

At 18:17 1/29/05, VE3NEA wrote:
>I was wondering how the popular RTTY programs compare to each other in terms
>of decoding accuracy. To my surprise, a search on the Internet proved that
>such a comparison had never been performed, and I had no choice but running
>a series of tests myself. I downloaded PathSim from the AE4JY web site and
>generated a set of messages with AWGN, flat and selective fading, flutter,
>and multi-path delay. Then I decoded these messages with MMTTY, MixW and
>TrueTTY, and tried to count the errors.
>
>It was immediately obvious why no one did such tests before. Counting errors
>was a very time consuming task and, more importantly, was possible only at
>low error rates. At CER = 10% or so it was virtually impossible to match the
>two sequences of characters and tell the correct letters from the wrong
>ones.
>
>To solve this problem, I wrote an RTTY message comparison tool, RttyCompare.
>The program converts the transmitted and received text to the Baudot code
>and compares the two sequences using the standard dynamic programming
>algorithm, counts the missing and incorrect codes, and instantly calculates
>CER. It is robust enough at error rates as high as 50% and even higher.
>
>Equipped with RttyCompare, I had no problems completing my tests. The
>comparison results are available at http://www.dxatlas.com/rtty with a
>description of the testing procedures. RttyCompare can be downloaded from
>the same site, with source code.
>
>I am far from drawing any conclusions from the tests, this is just a request
>for a discussion. The procedures that I used must be verified by other hams,
>and the results must be independently reproduced. Now that the testing
>procedure is documented and a complete list of required tools is identified,
>everyone can do a similar test - perhaps with longer messages, more
>realistic PathSim profiles, and for a wider variety of RTTY programs
>(cocoaModem ?).
>
>73 Alex VE3NEA
>
>
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