Posted: 12/30/2014 7:25:50 PM EDT
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Tell me about it.
http://freedv.org/tiki-index.php Digital voice for HF. Anyone play with this yet? A local that I chat with on 2m simplex was telling me about this last night, so I downloaded it. I did hear a guy on 14.236 just a couple minutes ago, so it looks like I did get the receive configured correctly, but I wont have time to hit the PTT until later tonight at best. |
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Yes, I have played with it.
I worked a few people on it. It required much more signal than SSB. FWIW: the next release of SmartSDR (Flex Radio) due for release at the end of January is going to have FreeDV as a mode on the control panel. It's very simple to operate: you download the software and install it on your PC. You configure it. Receive Audio: From Radio and to Speakers Transmit Audio from Mic to radio So there are four audio settings unlike something like software for PSK or whatever. For a regular radio this will be the input to your sound card, then out to whatever you are going to listen on (speakers........) Then on transmit you will have your microphone and then the signal going back to the radio. Then you configure PTT on a com port. You plug a mic into your PC soundcard And you should be good to go. YOu can operate either digital or analog using the software and the PC mic. |
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I did this about six months ago or so. I got a new PC since then and didn't have this set up until you just asked about it.
So now of course I am having trouble getting PTT (what else is new ?) But am receiving and I can transmit by manually putting the radio into transmit but I have to figure out why I have no PTT> |
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There is also an online "QSO Finder" that you can use to make skeds for FreeDV
I started out playing with this, with a local guy. We got everything figured out and then I went on this QSO Finder, logged in and worked a few people from there. |
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I've used it, in fact I was one of the early adopters. I quickly lost interest. It requires substantially better than average band conditions, good enough that normal analog SSB will work with no trouble at all. Even under ideal conditions voice quality is inferior to even mediocre analog SSB.
IMHO the developers have concentrated too hard on achieving narrow bandwidth. This has limited the bit rates to 1600 bits/sec, which is why the voice quality is so poor. It would be much better at 2400 bits/sec. Their argument is that moving to a wider bandwidth just causes a more severe PAPR (crest factor) problem. I'm not sure I agree the trade-off is that pat. Also, like most digital voice comm's, it does not exhibit graceful degradation under marginal conditions. This leads to some nasty sounding squeak and garble rather than the noise fades experienced with analog comm's. One thing they have to get major credit for, however, is the development of the "CODEC2" voice codec. At equivalent bit rates it sounds nearly as good as the gold standard for low bit rate codecs, MELP, and also nearly as good as AMBE (the P25 codec). Unlike MELP and AMBE, it is open source and free to use. There's been some rumblings on the Google Group about doing a VHF version, but again they are going for low bandwidth which, IMHO, is just dopey. They are missing a chance to do in MELP and AMBE. If only they'd come out with 2400 and 3600 bits/sec versions for VHF and above. |