{"id":835,"date":"2012-12-18T07:56:59","date_gmt":"2012-12-18T05:56:59","guid":{"rendered":"http:\/\/dh5ym.hopto.org\/wiki\/?p=835"},"modified":"2013-02-08T18:43:37","modified_gmt":"2013-02-08T18:43:37","slug":"freedv-fdmdv2-digital-voice-shortwave","status":"publish","type":"post","link":"https:\/\/dh5ym.hopto.org\/wiki\/?p=835","title":{"rendered":"Freedv \/ FDMDV2 – digital voice shortwave"},"content":{"rendered":"

Since a long time David Rowe VK5DGR works on a open-source low-rate voice codec. This project is called codec2.
\nNow a variant of this codec is used in a amateur radio digital voice mode that was evolved out of the well known FDMDV software.
\nThe mode uses OFDM with 14 carriers DQPSK and 2 pilot carriers with twice the power modulated in DBPSK.
\nThe bandwith is 1kHz, so 2 of the signals would fit to 1 SSB channel. The datarate of the voice is 1375 Bit\/s + some data bits for callsign information etc.
\nIts intended that in the end this mode can also be used for DX connections. Lets see what live tests will bring. On 20m obviously the frequency 14.236MHz is used as center of gravity.
\nFor using the mode you would need either a two-soundcard PC (one for connecting a headset and one for creating the digital modulation signal) or a SDR setup with virtual soundcards. Currently a windows beta release can be downloaded as binary. For Linux you have to download the source and compile it on your own. David created a nice Makefile that downloads and compiles all dependecies.
\nYou find further information on the project page http:\/\/freedv.org\/tiki-index.php<\/a>.
\nAlso some videos are linked that show the operation and the audio quality of this digital mode.<\/p>\n

\"some<\/a>

some experiments with FreeDV and Quisk<\/p><\/div>\n

How the digital signal of Freedv\/FDMDV2 sounds like:
\nfreedv-test<\/a><\/p>\n

How the decoded audio sounds like (its only 1375bit\/s with 1kHz bandwidth!):
\nREC-0003<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Since a long time David Rowe VK5DGR works on a open-source low-rate voice codec. This project is called codec2. Now a variant of this codec is used in a amateur radio digital voice mode that was evolved out of the … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2,5,8],"tags":[],"class_list":["post-835","post","type-post","status-publish","format-standard","hentry","category-amateur-radio","category-digital-voice","category-linuxandcomputer"],"_links":{"self":[{"href":"https:\/\/dh5ym.hopto.org\/wiki\/index.php?rest_route=\/wp\/v2\/posts\/835","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dh5ym.hopto.org\/wiki\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dh5ym.hopto.org\/wiki\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dh5ym.hopto.org\/wiki\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dh5ym.hopto.org\/wiki\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=835"}],"version-history":[{"count":1,"href":"https:\/\/dh5ym.hopto.org\/wiki\/index.php?rest_route=\/wp\/v2\/posts\/835\/revisions"}],"predecessor-version":[{"id":863,"href":"https:\/\/dh5ym.hopto.org\/wiki\/index.php?rest_route=\/wp\/v2\/posts\/835\/revisions\/863"}],"wp:attachment":[{"href":"https:\/\/dh5ym.hopto.org\/wiki\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=835"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dh5ym.hopto.org\/wiki\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=835"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dh5ym.hopto.org\/wiki\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=835"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}