GNU Radio

Max Hyre writes "Apropos (!= man -k :-) RIAA, web radio, and other such data-dispersal disagreements, here's a new way to do it your way: a fully software-driven radio receiver; just strap some off-the-shelf DAC hardware into a generic computer, and let the software do the rest. While I can just barely spell `sideband', this looks like it could be more fun than any set you ever had before, especially after those in the know build up some kewl apps for the great unwashed like me. They're also dreaming of GPS, cellular phones, &c.. My only gripe is that the web pages proper don't seem to have any cookbook recipes for the hardware; maybe that's in the docs with the source, or maybe this is strictly for the experienced, for now."

Comments

Sounds interesting, there is a similar project out

[rickthewizkid]

Check out tapr.org and the DSP-10 project. It's a 2 meter ham radio that is defined in software, using the DSP board to handle modulation. I am saving my nickels and dimes to buy a kit, and it seems interesting. Also, since it's all defined in software, it can be connected to a transverter and the output can be SSB, FM, etc and the software for the PC can be programmed to take into account that the transverter is making the 2 meter rig into say a 10 meter or microwave rig.

-RickTheWizKid

Re:Cool, but pointless

[Lumpy]

Great! you are right on....

so where do you get DSP's that are field programmable in C?
and connect easily to a computer costing less than $200.00 in parts to cover from DC to 10Ghz?

DSP's are good for end products that are to be released to the sheep. This is better than any DSP ever created and will do it better than any DSP ever created for research and expierimentation. doing that with a DSP is near impossible for the amateur and is 100% impossible without breaking the law for poor expierimenters.

DSP's suck for research by the hobbiest..This process is best.

be sure to include the entire costs of development before offering your opinion as to weither an expensive alternative is better. (DSP's are ungodly expensive after you factor in the programming software,devkit, and required hardware all purchased legally... TI's devkit costs over $20KUSD that has all the tools available (the student kit doesnt do 1/2 of the pro devkit.)

Hardware Geeks

[Alien54]

This looks like it very much as hardware geek think. very cool, very esoteric.

It is not pointless, however, but it is very bleeding edge. I can see this being more practical as processor speed improves.

Maybe eventually there will be something like a box with a firewire connection or something.

You know some companies will freak if people start producing software to receive HDTV, Satellite Radio, etc. HDTV is supposed to be the standard nation wide by 2006(??). This ties in with the ability in HDTV to block recording of certain programs, etc. if you have a digital recorder. This will also tie into that bill Sen Hollings introduced.

So this is all part of a somewhat larger picture.

Re:The forbidden fruits of radio

[gbnewby]

In the US, radio receivers and scanners are forbidden from receiving in the cellular phone bands (not that hard to get around by buying a radio elsewhere or modifying your own).

Spread-spectrum technology, as used in wireless phones, especially 3G wireless and other communication, is generally inaccessible to your generic home scanner or ham setup. Also, it's often digital, which again means a home scanner or ham is out of luck.

Enter GNU radio. This sounds like it will easily enable receiving the "forbidden" bands, and give a lot of computer power to re-assemble the spread-spectrum signals. I don't know if this is the intent of the developers, but the potential for bypassing existing radio "security" (really, security through obscurity & legalese) seems strong.

This won't let you listen to cellular.

[wowbagger]

I do this for a living, and I can tell you this won't help you listen to cellular.

First, all they are doing is taking the 455kHz IF from an existing radio, digitizing it, and using the computer to do the demodulation. Thus, if your radio won't receive the cellular band, your computer won't either. And if your radio can tune into the cell band, you can listen to AMPS without a computer - it's just narrowband FM.

Now, if you are talking about GSM, PCS, CDMA, or anything other than AMPS, then you will need more than just a receiver that can tune those bands. CDMA is spread over 1.5MHz of spectrum - unless your radio has an IF that wide you are out of luck.

GSM and PCS (which is just GSM at a different frequency) is narrowband, but it's still more complicated than FM- you need to be able to receive the complex (in the a + (srqt(-1))w sense of the word) waveform, and pull the bits out of the air. Then, you need to decode the protocol, run the vocoder algorithm, and generate the audio. We use TI C6X DSPs capable of 1.6BOPS, with special opcodes to help the decoding, and Special chips to do the grunt work and it still takes a lot of work to get it to run in real time.

Now, if you are a ham, and you want to do sideband, PSK31, or other modes, this is a great thing. But don't expect to be able to monitor your neighbor's phone with it.

Besides, if you ever HAD monitored cellular, you't realize it's about as interesting as watching grass grow.

Heh.

[Chris Johnson]

I'm sorry, but this is real wimpy for GNU.

My notion of GNU Radio would be simple and inexpensive free FM BROADCASTING. Of course, the FCC has issues with that... if you pay attention to the micropower FM scene, it's actually quite similar to what GNU stands for. It's about empowering people.

The catch is, it's pretty easy to screw up an adjacent station if your signal is screwy and out of spec.

The low-power FM movement is worth your attention- if you're even reading this article you probably 'get' the importance of micro/local broadcasting. It should come as no surprise that corporate radio has been using Congress and the government to try to stamp out even the possibility of people using local FM broadcasting to provide alternatives- it mirrors what other content industries have been doing with more Slashdot attention. In December 2000 Congress passed an appropriations bill with a rider that was snuck in to halve the number of low power FM licenses the FCC could legally issue. Not only was corporate radio behind this- NPR also supported the illegalization of low power FM broadcasting. McCain (R-AZ) has introduced a bill to counter this and support low power FM again. Furthermore, on February 8, 2002, the Court Of Appeals struck down language in this anti-LPFM act which had prohibited the FCC from issuing a license to anyone who had ever previously been involved with pirate radio. The court held that this was unconstitutional. (funny how both in the judiciary and Congress, these guys are forced to deal with all types of injustice and power grabs, not just the sorts that are close to the hearts of Slashdotters ;) )

These people are the other side of the coin: transmitters from microwatt to 500 watts and kits for all kinds of nifty things like subcarrier decoders, shortwave, the aviation band etc. I don't know anything about them but their catalog but it would make any true geek absolutely drool, with all the build-it-yourself devices to do arcane and amusing things, and the flashy computerised rackmountable transmitters. Too cool.

Multiple channels

[Animats]

Software radios can receive multiple channels at once, provided enough compute power is available. Cell sites use this to receive hundreds of channels without having hundreds of separate receivers.

This has some possibilities. One is a radio that listens to the entire FM band and, quickly and automatically, builds an MP3 music library of popular music. Legal, too. (Audio Home Recording Act)

Add-ons to this project could include automatic song identification (there are song-signature databases for this), use of multiple copies to recognize and remove announcer blithering, and intelligent audio cleanup from multiple copies.

Great open-source project for audio people. Nice device for cars, too.

Watching grass, er, multiply

[leonbrooks]

Besides, if you ever HAD monitored cellular, you't realize it's about as interesting as watching grass grow.

That depends on whether you've got a `transmit' button or not.

One place I worked at left a scanner running in the main office (the boss was more than a bit weird), and one day we got an entire 20-minute conversation between husband (on mobile) and wife (on land-line) discussing the previous weekend's partner-swapping exercise, ratings and so on, exploring the prospects for a repeat and so on.

Towards the end wife asked if it was wise to discuss this on the 'phone and husband returned copious assurances that since he was on a mobile (but evidently sitting still) the conversation would be chopped up across channels and nobody could make head or tail of it.

And me with no transmit button. Sigh.