[RTTY] LMS Notch filter

Dave AA6YQ aa6yq at ambersoft.com
Fri Feb 24 17:19:40 PST 2012

>>>AA6YQ comments below

-----Original Message-----
From: rtty-bounces at contesting.com [mailto:rtty-bounces at contesting.com]On
Behalf Of Kok Chen
Sent: Friday, February 24, 2012 7:46 PM
To: RTTY Reflector
Subject: Re: [RTTY] LMS Notch filter

On Feb 24, 2012, at 3:38 PM, Dave AA6YQ wrote:

> It's parameters were chosen empirically to
> optimize decoding of a -10db SNR (AWGN) .wav file produced by Moe AE4JY's
> PathSim application, with results assessed by Alex VE3NEA's RTTYcompare
> application. This configuration yields a 16% character error rate (CER),
> compared to the standard profile's 41% CER, the hypersensitive profile's
> CER, and the EU1SA profile's 53% CER.

As seen from Figure 4 of the Extended Nyquist Filter article that I just
posted a few minutes earlier, the Raised Cosine and Matched filter both
comes up with better than 13% character error rate for a -10 dB SNR.  So
there is another level of improvement you can easily make if you can modify
the FIR filter coefficients in MMTTY.

>>>I have the MMTTY source code, but since Mako-san JE3HHT re-engaged to
develop MMTTY 1.68A, I am reluctant to initiate a major effort within his
code base without his approval -- which I have requested, but not yet
received. As your posts have pointed out, there are many opportunities to
improve MMTTY's RTTY decoding.


         Dave, AA6YQ

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