[VHFcontesting] FreeDV digital voice

Anthony Cutler 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.

73, AD7N

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