Hi David Helmut and I are doing experiments with all available modes of freedv (700,700b,700c,800xa and 1600) on 80 metres. This band is very difficult because I have a lot of local noise. We will report on our results as soon as possible, currently, we have problems with the transmission, so we could not yet make systematic experiments.
But I have some questions: From my point of view, we have two different parts for the HF DV problem: 1) the codec2 for the encoding of the voice. 2) the modulation for sending over the highly disturbed path over the ionosphere. In local experiments, I have heared, that the codec 700c sounds quite comparable with the 1600, the audio is quite "voluminous" in contrast to 700 and 700b. To me, this is a question only of the features of the codec2 but not of the modulation. Is that true? On the other hand, the modulation decides, wether the codec2-data can be successfully decoded even in critical HF conditions. Is it true, that the decoding mainly depends on the demodulation capability of the selected modulation? So, I think, that the codec2 mainly decides on the amount of digital bits which has to be transmitted and decoded and the modem decides how and if one can reconstruct the bits for the codec2. Is it true then, that one can concentrate on the modem technique for best HF results? Or is the relation between the codec2 and the modem so entangled, that one has to see both at the same time? The question arouse, when Helmut and I used the codec2 in 700c, but switched from 700c to 800xa, which in my understanding is just a different modem, not a different codec2. Greetings Alfred ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
