The modem program fldigi has been updated to version 3.21.69 and has
been posted for Windows, Linux, Puppy and OS X operating systems,
http://www.w1hkj.com
Improvements to the program which might be of interest to this forum:
* Transmit waveform shaping improved with a narrower spectrum.
* Transmit precursor signal (toggled space mark signal) to allow ATC
estimators apriori tracking.
* Receive filter and optimized ATC bit detector, provides a CER of
0.0892 when receiving a CPFSK signal at -9 dB s/n.
* RTTY signal browser uses identical filtering and tracking as the
primary decoder.
These improvements were the joint effort of Stefan Fendt, DO2SMF, and
myself, W1HKJ. We had encouragement and welcome guidance from Kok Chen,
W7AY, and David G3YYD. Thanks for the steerage.
Hope to work you on the air.
73, Dave, W1HKJ
Notes:
1. ATC - Automatic Threshold Correcting
2. CER - Character Error Rate
3. CPFSK - Continuous Phase Frequency Shift Keying
4. Test signal generated using fldigi's wav recording and PathSim.exe.
Errors checked using RTTY_compare.exe and a yet to be released Linux
program, comprtty.
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