Wikipedia has a definition and discussion of software defined radios. The page also has a link to a list of software-defined-radios, obviously incomplete as it does not include Flex. The link is at the bottom of the article in the section "See Also". It also has a link to a list of web-based software-defined receivers in the section "External Links".
A Google search turns up more definitions of SDR. There seems to be a difference of opinion whether code stored in a ROM (fixed or reprogrammable) qualifies as software. The military JTRS (Joint Tactical Radio System) program is a long running program to produce a common radio platform (the hardware) to run all the military radio waveforms (the software). Their experience provides solid evidence that the software is not necessarily easier to create or to change than is the hardware. For what it's worth, JTRS is understood to be an SDR and the software is stored in ROM. As this discussion thread has highlighted, there are many ways to implement some of the functions of a radio in software. I happen to be quite fond of the way Flex Radio Systems does it. Thurman Irving, AA5KK -----Original Message----- From: flexradio-boun...@flex-radio.biz [mailto:flexradio-boun...@flex-radio.biz] On Behalf Of Dave Gomberg Sent: Monday, December 12, 2011 12:55 PM To: flexradio@flex-radio.biz Subject: [Flexradio] SDR defined At 15:10 12/11/2011, Jim Jerzycke wrote: >We're discussing it because a lot of people don't have a clear >understanding of what a Software Defined Radio actually is. Well, when I wrote a talk about SDR I defined an SDR this way (talking about rcvr, but xmit is similar): A radio has five jobs: 1. Amplification (picowatts from the antenna to watts to the headphones or speakers) 2. Band selection (to permit adapting some later functions to a narrower frequency range) 3. Frequency reduction (from MHz to KHz) 4. Tuning (to reduce the region of focus from many KHz to a few Hz or KHz). 5. Demodulation (to recover the signal from its processed form (think FM for example)) A conventional radio accomplishes ALL these functions in hardware. Because of speed/bandwidth restrictions, ALL current radios do 1, 2, 3 in hardware or special purpose microchips. I said it was an SDR if it used software or upgradable firmware to accomplish any of 1-5. Notice that the FCC appears to believe that software is easier to upgrade than hardware. If you think about most MARS mods, this is clearly wrong, but the FCC gives diode-lifting a free ride because it is a hardware mod. And nowhere does the FCC consider data mods. If band frequency and mode limitations are governed by a table, then changing the table is NOT a software mod. Hmmmm. And firmware mods are apparently considered hardware because they are implemented in a ROM, not code on a hard disk or floppy or CD. Suppose it is an EAPROM? This is clearly an area that needs rethinking by minds more technologically competent that those used so far. -- Dave Gomberg, San Francisco NE5EE Programming since 1959 All addresses, phones, etc. at http://www.wcf.com/ham/info.html ----------------------------------------------------------------- _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flexradio.com/ Homepage: http://www.flexradio.com/ _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flexradio.com/ Homepage: http://www.flexradio.com/
