Wow Adrian it's really coming along quickly! Well done :-) Combined with the latest crop of duplex SDRs, I can see this work opening up experimentation in the VHF/UHF bands.
Some thoughts: 1/ Codec 2 2400A and 2400B were designed to work on VHF/UHF, and 2400A to substantially outperform FM and current digital voice systems at low SNRs: http://www.rowetel.com/wordpress/?p=5219 They're in the FreeDV API already. 2/ Have you done any BER versus SNR (Eb/No) tests to evaluate the performance of the modems you are using, e.g. comparing performance to theoretical? We have found many existing VHF/UHF digital voice systems have modems that perform poorly. Gains of 10dB are possible with the right modem/waveform design. 3/ RpiTx would be an interesting option for the TX side: https://github.com/F5OEO/rpitx Cheers, David On 17/10/19 10:30 pm, Adrian Musceac wrote: > Hi, > I made some more progress working on my application[1]. > First of all, it is now possible to run it headless (maybe even > daemonized) and control it remotely using a telnet client. > Second, I have added support for mixed mode repeater (Codec2/FM or > viceversa or any combination of modes like wideband > Opus/Codec2/FreeDV/SSB etc.). > > The repeater can be connected to a VOIP server using the low latency > Mumble voice protocol (known especially for high-performance gaming). So > it is possible now to connect multiple repeaters together by putting > them on the same VOIP channel (this can be controlled via telnet as > well, although it's stil work in progress). They operate in full duplex > mode, so a VOIP user can talk at the same time as a radio user and the > two audio streams will be mixed together and broadcast. The > FreeDV/Codec2 radio frames are transcoded to Opus at very high bitrates > (~48 kbit/s) for VOIP transport. This may cause some small delays. > > I haven't really had time to test the cross-mode repeater so could use > some help there from interested parties. > > [1] http://qradiolink.org > > Cheers, > Adrian > > > > > _______________________________________________ > Freetel-codec2 mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
