[VHFcontesting] FreeDV digital voice
acutler22 at yahoo.com
Thu Dec 13 12:52:21 EST 2012
Some of you might find this interesting: freedv.org
It's a ham-developed digital voice software implementation (open source/free). While targeted for HF, it's got potential on VHF/UHF/SHF SSB - it uses existing radios, just requires a soundcard interface hookup (If you're setup for FSK441 or PSK31 you're all set). Because it's digital voice though, it needs a USB headset or a second soundcard.
it's got some interesting benefits/features (copied from the site):
* Codec 2 voice codec and FDMDV modem
* 50 baud 14 QPSK voice data
* 1 Center BPSK carrier with 2x power for fast and robust synchronisation.
* 1.125 kHz spectrum bandwidth (half SSB) with 75 Hz carrier spacing
* 1400 bit/s data rate with 1375 bit/s open source Codec 2 voice coding and 25 bit/s text for call sign ID
* No interleaving in time or FEC philosophy resulting in low latency, fast synchronization and quick recovery from fades.
* 44.1 or 48kHz sample rate sound card compatible Key Features:
* Cross platform, runs on Linux or Windows
* Open source, patent free Codec and Modem that anyone can experiment with and modify
* Waterfall, spectrum, scatter and audio oscilliscope displays.
* Adjustable squelch
* Fast/slow SNR estimation
* Microphone and Speaker signal audio Equaliser
* Control of Transmitter PTT via RS232 levels
* Works with one (receive only) or two (transmit and receive) sound cards, for example a built in sound card and USB headphones.
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