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Open Source Two Way Radio

This talk will describe how an open source codec, modem, and open hardware can be used to improve two way VHF radio by a factor of 10.

Push to talk two way radio is commonly used for police, emergency services, and the construction industry, with a world wide market of 50 million units/year. It can be used with or without base stations, and has a range of 10s of km.

Several two way digital radio systems exist and are in common use today, however these are hobbled by the use of closed source codecs, which add significantly to the radio costs, and prohibit experimentation. There is frustration throughout the radio industry with closed source codecs.

A team of open source developers has been working on open two way radio systems. The team has demonstrated a performance increase of a factor of 10, which can be used in a variety of ways:

Transmit power can be reduced
Battery life can be extended
Relatively high bit rate digital data can be sent
High quality speech, or variable rate speech coding and quality
The range of the radios can be extended
The cost of the radio hardware can be greatly reduced due to low power, simple hardware, smaller batteries, and no codec license fees.

The use of Software Defined Radio (SDR) hardware is bringing the price of the hardware down, and open software is improving the functionality and performance. The new, open two way radio protocol requires a new, open hardware radio design. Fortunately, this can be relative simple, as most of the signal processing can be done in software.

David Rowe

David Rowe has 25 years experience in the development of DSP-based telephony and sat-com hardware/software. David has a wide mix of skills including software, hardware, project and business management, and a PhD in DSP theory. In 1968 at age 9 months he was crawling towards power points, and it’s been all downhill since then. He received his first Amateur Radio license at age 13, and was programming assembler on his first Z-80 based computer in 1982. In 2006 he quit an executive position in the satellite communications industry to become a full time open source developer. Since then David has worked on open hardware and software projects in VOIP, developing world communications (, echo cancellation, speech compression, and digital voice over HF radio. David's other interests include his popular blog (, Electric Vehicles, travel, the Skepticism (critical thinking) movement, Amateur Radio, and swanning around Adelaide on his bike drinking lattes. David has been a popular speaker and red wine drinker at every since 2008, and in 2012 his presentation on Codec 2 was voted best of conference.

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