Hi,
Now that the first steps are underway for chosing and implementing better FEC systems, work also has to be done to create a lower bitrate version of the GMSK modem. The GMSK-modem uses two DSP FIR filters. Both come from the pcrepeatercontroller project of Jonathan G4KLX - in the "modulation" chain, there is a filter that applies a gaussian filter. It seams to be created using this mathlab function: gaussfir(0.5, 2, 10) - in the demodulation chain, there is high-order filter blocking everything below 2400 Hz. (A 4800 bps digital signal sending "10101" has a maximum frequency of 2400 Hz). I do not have the exact parameters of that filter. Is there somebody with more DSP knowledge then myself who can do the create the same kind of filters for 3600 and 2400 bps modems? (perhaps we even do still lowerbitrate modem later). The audio is sampled at 48000 Hz. (I have some basic DSP skills and I know there are certain websites which can be used to create FIR filters, but I prefer this is best done by somebody who has some more background knowledge of DSP then myself). If somebody is interested in doing this, feel free to let us know. 73 Kristoff - ON1ARF ------------------------------------------------------------------------------ Don't let slow site performance ruin your business. Deploy New Relic APM Deploy New Relic app performance management and know exactly what is happening inside your Ruby, Python, PHP, Java, and .NET app Try New Relic at no cost today and get our sweet Data Nerd shirt too! http://p.sf.net/sfu/newrelic-dev2dev _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
