Software-Defined Radio For $11

Malvineous writes "Don't have $1500 to drop on a USRP? A Linux kernel developer has discovered that a Realtek digital TV tuner chip has an undocumented mode that turns it into a software-defined radio, with a frequency range of 64-1700MHz. The going rate for one of these USB devices can be as low as US$11. If you're unfamiliar with software-defined radio and have 20 minutes to spare, Balint Seeber has a great video introduction."

Comments

/.'d - google cache

[Anonymous Coward]

http://webcache.googleusercontent.com/search?q=cache:fRixFRVwNjoJ:sdr.osmocom.org/trac/wiki/rtl-sdr+sdr.osmocom.org/trac/wiki/rtl-sdr&cd=1&hl=en&ct=clnk

(which is also slow as zark. anyone manage a mirror?)

Too long

[ebcdic]

I'm unfamiliar with software-defined radio, and I don't want to spent 20 minutes watching a video. I hate this trend of using a video for something that could be explained in text that I could read in a fraction of the time.

Re:Too long

[Bananana]

yep. and the trend is not limited to April fools' pranks.

Re:Too long

[shish]

Watching the video now, it appears to be "dump ALL the radio signals to disk, for later analysis", so you can then use software to pick out audio / text / morse code / etc signals

Re:Too long

[trout007]

I found this great new site you may be unaware of. It's called Wikipedia. It is kinda of like an online encyclopedia that has brief summaries of almost anything. Check it out I'm sure you will like it.

http://en.wikipedia.org/wiki/Software-defined_radio

Re:Too long

[MinusOne]

Would it really have been that hard to embed the Wikipedia link in the article? Sure I can look this some up, but someone is trying to explain it to me and its just one stupid link.

Re:Too long

[Alsee]

In a "normal" radio-using device you have an electronic circuit to detect or create an exact sort of signal at a particular frequency range. For example you have one sort of circuit to detect FM tpy signals and a completely different circuit to detect AM radio signals, and a TV has circuitry that transforms exact-TV-format signals into the needed picture and sound signals. The advantage of these specific electronics is that they are cheaper and use less power.

A software defined radio picks up (or transmits) radio waves basically as a graph. A digitized wave form. A software defined radio uses a CPU to examine (or create) the radio wave. This means that simply by loading in the right software you can detect (or create) absolutely any sort of signal at all. You have one circuit that can handle up AM, FM, TV, cellphone signals, wifi signals, or anything. They can also use advanced digital methods to eliminate various kinds of noise.

The downside of software defined radio is that the circuitry needs to be bigger, faster, and more power-hungry to handle fast computation.

Software defined radio has the government worried and paralyzed. The government is used to individually regulating the frequencies and power levels and signal characteristics of each kind of radio-using device. An AM/FM radio specifically does not pick up police or cell phone frequencies, and things like CBs and walkie-talkies and cellphones and baby monitors all have specific power levels and specific frequencies they can broadcast on, and they only broadcast in specific radio formats. And those limits are hard-baked into the devices by their exact circuitry. Software defined radio throws that entire idea out the window. A software defined radio is going to have some inherent power limit based on the exact hardware, and some minimum and maximum frequency range based on the hardware, but generally it can handle a very broad range from low frequency bands to high frequency bands, and they can send/detect absolutely any radio format over that entire range, and they can do it at full power. There's no way to regulate "don't detect police/cell frequencies", and no way to regulate "don't broadcast FM on what is supposed to be an AM band", and there is no way to regulate different power levels on different bands. Once you sell a software defined radio, the end user can load in any software they want.

Software defined radio is revolutionary. It is incredibly flexible. And that flexibility is exactly the "problem" for government regulators.

-

Re:Too long

[Polo]

I found this particular video showed me what you could do in a visual way I wouldn't have picked up by reading about it.

Yes, I agree that sometimes you can't watch a video where you could read text though.

Re:Too long

[Auroch]

Actually, I think the point the OP was trying to make was something like ... "Why not just explain it in a sentence or two IN THE F*SKING ARTICLE instead of linking a video or an external source".

Re:Too long

[bmo]

Software defined radio has the government worried and paralyzed. The government is used to individually regulating the frequencies and power levels and signal characteristics of each kind of radio-using device. An AM/FM radio specifically does not pick up police or cell phone frequencies, and things like CBs and walkie-talkies and cellphones and baby monitors all have specific power levels and specific frequencies they can broadcast on, and they only broadcast in specific radio formats. And those limits are hard-baked into the devices by their exact circuitry. Software defined radio throws that entire idea out the window. A software defined radio is going to have some inherent power limit based on the exact hardware, and some minimum and maximum frequency range based on the hardware, but generally it can handle a very broad range from low frequency bands to high frequency bands, and they can send/detect absolutely any radio format over that entire range, and they can do it at full power. There's no way to regulate "don't detect police/cell frequencies", and no way to regulate "don't broadcast FM on what is supposed to be an AM band", and there is no way to regulate different power levels on different bands. Once you sell a software defined radio, the end user can load in any software they want.

Anyone with the technical knowledge can do any of these tasks in hardware, for not a lot of money. There are entire libraries of books and technical articles on how to broadcast/receive on any band, even "forbidden" ones like 800MHz cellular. I remember an article in Popular Communications for a down-converter you could build to listen to 800MHz back in the early 90s that simply screwed into the BNC of your scanner in line with the antenna.

BFD.

>implying it's somehow illegal to listen to bands outside of AM/FM

What the hell are you talking about? Beyond the Cellular legislation, any and all bands are open for reception. It's your right to intercept radio waves on whatever spectrum and you don't need a license to do so. You only need a license to transmit on licensed spectrum.

>cannot regulate power levels and bands

As if they weren't able to regulate for the past 80 years?

Protip: If you are transmitting 1kw, and transmitting in a band you shouldn't be in, it won't be the feds who track you down, it will be the licensed operators who will find you and turn your ass in to the feds and they'll be happy to do so.

The only reason why Joe Trucker doesn't get turned in with his 1kw linear on CB is because he's a moving target. Anyone else sitting in his basement throwing shitty harmonics up and down the bands can be found.

Also, software defined radios are not amplifiers. You are conflating one technology with another.

The amount of wrong in your post is staggering.

--
BMO

Re:Too long

[Anonymous Coward]

What the hell are you talking about?

1) The hard bit of any radio, especially important for transmission, is low noise band filtering, precise tuning and mixing to convert to/from AF. This all involves a lot of careful analog design and cannot be replaced by the S of SDR. Sure, the oscillator can use DDS, but that's not going to be done by wasting your computer's CPU cycles and it wouldn't make any difference anyway;

2) For analog modes, it's arguably easier to build a circuit than write decoding software. For digital modes, you're either running software on your desktop/laptop or you're running software on the radio's CPU. The only relevant questions are a) whether the modulation is documented - the answer is usually "yes" except for military; b) the keys for any encryption are available to you - if not, being able to implement an SDR makes not a hoot of difference;

3) Yes, you can do some fine DSP with a modern CPU but only an idiot thinks this is a substitute for a good antenna and (per 1) front-end.

SDR is the e-m equivalent of the "winmodem" in dial-up days: yes, you have the opportunity for a lot more versatility, but only by creating something dumb and offloading the work to a less power-efficient general purpose computer which may or may not have something better to do.

Re:Too long

[girlintraining]

The only reason why Joe Trucker doesn't get turned in with his 1kw linear on CB is because he's a moving target

Actually, it's because the government just doesn't give a sh*t about CB radio frequencies. But given that it uses an incredibly simple modulation scheme, it can easily be traced and tracked in realtime. All you need to catch "Joe Trucker" is three antennas spaced one wavelength or more apart and you can get a fix on their position. They may be a moving target, but they're moving along a fixed path: The road. Find a guy heading northwest in the same direction as the highway and you just hop on the road a few exits up and join the flow of traffic. He'll talk again, and when he does... oh look, it's the guy 50 feet in front of you in the left lane... *flips on lights* Goodbye 1kW transmitter, goodbye trucker.

Be more concerned about frequency hopping mobile devices that use a PRNG to communicate with another device over a range of frequencies and encoding techniques... That requires a LOT more equipment to sort out where the signal is coming from. Actually, that's pretty much what the military does... o_o

Re:Too long

[LWATCDR]

Sorry but why complain because someone didn't know you knew what software radio was? This is Slashdot News For Nerds not CNN. If someone posted a story about AMD would you complain that they didn't include a wikipedia link to AMD?
I just don't think that it is outside of reason to expect someone reading slashdot to google something they do not understand.

Re:Too long

[Grieviant]

The modern definition of 'radio' refers to any device that uses wireless to transmit / receive an electromagnetic signal. Your wifi modem, bluetooth device, smartphone, TV, etc., are all radios. It's not limited to traditional FM radio from 88-108 MHz. Pretty much all radios are using some form of digital communications these days, as opposed to analog modulation with FM radio. Software defined radio really isn't anything special - the low frequency part of the radio (from IF down to baseband) is handled with a digital signal processor that can be programmed to handle many different formats. It's a natural evolution of digital communications that gets tossed around as a buzzword.

Re:Too long

[superdave80]

So you've managed to deduce that software defined radio is a radio defined in software? Awesome.

Re:Too long

[Goaway]

This has nothing to do with April fools', Slashdot is just late on the uptake as usual.

Re:Too long

[DrVomact]

I'm unfamiliar with software-defined radio, and I don't want to spent 20 minutes watching a video. I hate this trend of using a video for something that could be explained in text that I could read in a fraction of the time.

Amen, brother. I figured that my aversion to video "tutorials" or "reviews" or whatever was just cranky old me being out of touch with the rest of the world again, so I wasn't going to say anything. But yeah, I am very sick of people talking and mugging for the camera instead of just writing a couple of clear concise paragraphs. The written word is random access. I can quickly skim a few paragraphs to see if this is what I'm looking for, I can read a lot faster than some fool can talk, and I if I just need one particular piece of information I can find it much more quickly in a written document than a video. I reserve particular disgust for people who try to demonstrate complex procedures, but have no idea about lighting or camera angle, so that the critical stuff is always done either in murky darkness or hidden behind the guy's hand.

Videos suck time. You have to sit in front of the monitor and watch while some guy natters on about whatever the subject is. Even if the video truly contains important reference information, you can't just watch it once, then later quickly go back to the critical part that you forgot. You have to try to find the right place to start playing the video. Again. You can't search a video for key-words. You can't print a video for later reference, or print a page to give to a friend who has a similar problem, and needs just a bit of key information. You can just send him the link, and invite him to waste his time.

What I truly fear is that the trend to videos is just another sign of cultural degeneration: it is part of the decline of literacy, of regard for the written word, and of the analytical thought that is possible only by means of the written word. So I don't look for a reversal of this trend any time soon. It's just going to get worse, along with everything else.

Re:Too long

[ChrisMaple]

SDR makes possible "brick wall" filters that aren't practical with analog circuits, and that are more stable over temperature and time than is possible with analog circuits. Software doesn't drift. Physical inductors have limited "Q", crystals and mechanical resonators have "spurs", and so forth and do on.

Re:Too long

[pz]

Software-defined filters can be arbitrarily good. Hardware filters are much more severely cost-limited. Sofware filters can be a-causal (assuming you are doing post-hoc processing) with characteristics impossible to build in hardware, like zero phase delay for all input frequencies. You can build 100-pole filters in software; sure you can do that in hardware, but it's going to get very expensive, large, and potentially noisy. You can build filters with frequency characteristics that *exactly* match the design parameters, not merely to within the tolerances of the components you use. Software filters *add* *no* *noise*. They have *zero* temperature drift. They have *zero* aging effects. They have essentially infinte power supply rejection. They don't suffer from interference. They can be re-programmed on the fly. They can be crazy non-linear (eg., if you watched the linked video, you can create a softare filter to detect and block whistlers only when they're happening and only affecting the frequencies where the whistlers are, removing only the whistler signal and nothing else, including the background; good luck doing that in analog). You can get close to all of these characteristics in pure analog hardware, but it is far more difficult and far more expensive than doing it digitally.

Given how inexpensive digital hardware has become, most of the assumptions that go into creating standard analog reciever and transmitter hardware need to be re-examined. On the reciever side, for example, the only reason you have an IF stage is because it's prohibitively expensive to use a non-superhet design and get the same performance ... unless the signals are processed digitally.

Have you seen the amazing (and highly non-linear) filters available in Photoshop for processing images? Imagine applying the same sort of technology to radio: difficult things become easy, and radical things become possible.

Re:Too long

[wagnerrp]

I'm sure 99.999% of the population who thinks "radios" are something they're listening to music on have exactly zero reason to know what a software defined radio is. The rest remainder of us who actually understand technology can use whatever terminology we see fit.

Re:Too long

[Technician]

All you need to catch "Joe Trucker" is three antennas spaced one wavelength or more apart and you can get a fix on their position

My rabbit hunting days was done with 4 antennas only 1/4 wave apart. Working in pairs, they were added with a 1/4 wave delay switched in and out of each antenna. If the signal was inline with an antenna pair, one direction added in phase and the other added out of phase. This modulated the carrier based on direction. Signals from the side of one pair remained un modulated, while the pair 90 degrees to the first pair provided maximum modulation. An XY scope display showed the relative modulation and phase info to give a decent relative bearing for mobile turkey hunting. Working with an active partner to flamebait a turkey, the silent DF partner usualy had little trouble finding a mobile or base target.

Re:Too long

[tlhIngan]

Software defined radio has the government worried and paralyzed. The government is used to individually regulating the frequencies and power levels and signal characteristics of each kind of radio-using device. An AM/FM radio specifically does not pick up police or cell phone frequencies, and things like CBs and walkie-talkies and cellphones and baby monitors all have specific power levels and specific frequencies they can broadcast on, and they only broadcast in specific radio formats. And those limits are hard-baked into the devices by their exact circuitry. Software defined radio throws that entire idea out the window. A software defined radio is going to have some inherent power limit based on the exact hardware, and some minimum and maximum frequency range based on the hardware, but generally it can handle a very broad range from low frequency bands to high frequency bands, and they can send/detect absolutely any radio format over that entire range, and they can do it at full power. There's no way to regulate "don't detect police/cell frequencies", and no way to regulate "don't broadcast FM on what is supposed to be an AM band", and there is no way to regulate different power levels on different bands. Once you sell a software defined radio, the end user can load in any software they want.

Not really. You can receive any frequency you want - you can buy equipment that very easily receives 100kHz-3GHz, legally.

The only trouble is with transmit, and the FCC controls intentional radiators. And no, government is not worried about it because there are some Very Nasty Fines for transmitting illegally. And they're levied on you, the operator, not the equipment manufacturer (though they can be found liable for making the equipment as well if its sole purpose was to do it, or even lose FCC certification). Pirate radio? That's really small potatoes.

Heck, the government has allowed many people to build their own radio transmitters legally and encourages people to do so legitimately - for the cost of obtaining the appropriate license (which is really quite minimal - if you can build your own transmitter, you can afford the license). It's called amateur radio and it really gives people full flexibility in building intentional radiators.

But receiving is always free. And the 800MHz cell law is hopelessly obsolete since no one uses AMPS anymore. Decoding digital transmissions is a lot harder, especially since there are now over a dozen frequency bands to which a cell call can be transmitted

And transmitters also have the limitation that they're fairly narrowband devices because the amplifiers tend to not have huge bandwidths. At least if you don't want to generate such crappy output that makes it even easier for people to find you.

SDR is revolutionary, yes. Even the government is using SDR technology as part of their SIGINT programs because they're very effective at scanning huge swaths of frequencies at once and isolating signals. And they're quite cheap - a whole bank of SDRs packed into a rackable unit isn't that expensive and can gather easily 24+ different freqeuncies at once (at 192kHz bandwidth each - using cheap-ass 192kHz/24bit audio ADCs used for consumer electronics). The beauty of this is as long as the signal you're looking at is less than 192kHz wide, you can pick it up. And TV's pretty much one of the few signals that requires a bit more bandwidth (6MHz).

Re:Too long

[Anonymous Coward]

Software-defined filters can be arbitrarily good.

Only for sufficiently small bandwidth and sufficiently small variation in signal power.

Ideally we'd plug an antenna straight into an ADC of infinite resolution to simultaneously pick up everyone from the broadcaster across the street to the QRP Siberian ham, sample at twice the highest frequency desired, and have infinitely cheap CPU cycles to deal with the 600 million samples a second which result up to VHF (good luck with UHF and beyond!).

In practice, like I said in my first post:

The hard bit of any radio, especially important for transmission, is low noise band filtering, precise tuning and mixing to convert to/from AF.

For receiver-only applications, an imprecise tune could be mitigated against with more CPU-wasting software processing.

If you wanted to go wild you could try to transmit by connecting a DAC directly to your matched antenna. Explaining why this isn't done is left as an exercise for the reader.

On the reciever side, for example, the only reason you have an IF stage is because it's prohibitively expensive to use a non-superhet design and get the same performance ... unless the signals are processed digitally.

Yeah, and the reason my DAB receiver costs ten times as much and sucks up at least ten times the power of my FM broadcast receiver is because simple analog circuitry is insufficient. Meanwhile good IF filters may still allow you to reject a loud adjacent channel and crank up the gain to give a better amplitude on the signal of interest for your ADC.

Imagine applying the same sort of technology to radio: difficult things become easy, and radical things become possible.

Yes, I'm a ham with a math background and last year I had a bit of an obsession with writing DSP filters, motivated by some horrible local use of PLT. A good frontend and especially a good antenna remain your primary aims - no amount of DSP with a bad front-end will give you a comparable output and we're back to the theoretical ADC of infinite resolution to pick up those minute changes in the presence of overwhelming noise.

Moving to the digital domain for AF filtering and demodulation is fine, but an FPGA is a better option than stressing a generic CPU, making it less an "S"DR anyway.

tl;dr no.

Re:Too long

[Anonymous Coward]

How do you think that a modern mobile phone works? Look at the radios in them. They are all SDR: a saw filter, an I/Q mixer and an analog to digital converter. Then it goes into a DSP. There are billions of mobile phones using SDR today.

WTF is that Acronym?

[Anonymous Coward]

How difficult would it have been to type Universal Software Radio Peripheral to avoid the obvious confusion with the Ukrainian Socialist-Revolutionary Party?

google cache link

[Nyder]

https://webcache.googleusercontent.com/search?q=cache:fRixFRVwNjoJ:sdr.osmocom.org/trac/wiki/rtl-sdr+&cd=1&hl=en&ct=clnk&gl=us

funny thing about this google cache link though, it's trying to load stuff from sdr.osmocom.org, which is currently slashdotted, so not sure if google knows what cache means anymore...

yes, sorry, https because that's how i roll baby...

Some info from the page

[Nyder]

rtl-sdr

DVB-T sticks based on the Realtek RTL2832U can be used as a cheap SDR, since the chip allows transferring the raw I/Q samples to the host, which is officially used for DAB/DAB+/FM demodulation. The possibility of this has been discovered by the V4L/DVB kernel developer Antti Palosaari.
Specifications

The RTL2832U outputs 8-bit I/Q-samples, and the highest theoretically possible sample-rate is 3.2 MS/s, however, the highest sample-rate without lost samples that has been tested so far is 2.8 MS/s. The frequency range is highly dependent of the used tuner, sticks that use the Elonics E4000 offer the best range (64 - 1700 MHz).
Supported Hardware

So far, the following devices are supported:

        ezcap EzTV668 USB 2.0 DVB-T/DAB/FM stick (Elonics E4000 tuner) (sources: AliExpress, Dealextreme)
        ezcap EzTV666 USB 2.0 DVB-T/DAB/FM stick (Elonics E4000 tuner, picture Download)
        Hama nano DVB-T stick (Elonics E4000 tuner)
        Terratec NOXON DAB/DAB+ USB-Stick (Fitipower FC0013 tuner)

People over at reddit are collecting a list of other devices that are compatible.

Other sticks based on the RTL2832U might be added in the future as well.

Re:Some info from the page

[Formalin]

The only one from the page with a link is $19.50 (dealextreme).

Where is the $11 one the summary refers to?

Not Searchable.

[solios]

Time isn't the issue for me. The issue for me is the fact that video "tutorials" feature voices that frequently grate on my nerves. Worse, the video tutorial cannot be quickly searched for the relevant information.

Seriously. I can find out if a text tutorial is relevant to the issue at hand in seconds. With video tutorials, I've typically closed the tab before the "host" finishes talking about how great he is, how great the software is, and what the tutorial is going to cover.

Re:Not Searchable.

[ColdWetDog]

I agree and feel like complaining this morning.

Come on, world. Shaky, unedited cell phone cam 'videos' are only slightly worse than slick, over prepared 'tuts' with dippy techo music in the background and pointless transitions (yeah, the ones on the very bottom of the picklist that nobody has used since 1981).

Just write it down. Show a static picture if you need to. Video is for things that move, not talking heads, not pointing fingers.

Now, if you don't mind. I shall take a nap. That was exhausting.

Re:Not Searchable.

[jamesh]

Time isn't the issue for me. The issue for me is the fact that video "tutorials" feature voices that frequently grate on my nerves. Worse, the video tutorial cannot be quickly searched for the relevant information.

Seriously. I can find out if a text tutorial is relevant to the issue at hand in seconds. With video tutorials, I've typically closed the tab before the "host" finishes talking about how great he is, how great the software is, and what the tutorial is going to cover.

Is the term "tl;dw" in common use? It would apply to any video over about 30 seconds (or any porn video over 60 minutes).

Re:better get

[Anonymous Coward]

Don't be a retard.

It's a TV receiver, it has no transmit capability. No FCC license is required to receive (almost) anything with a Class 15 device, which these are. The exception would be cellular telephony, but AFAIK there is no FCC license permitting eavesdropping on those -- you're either the (licensed) carrier who's actually handling the call, or you can't listen.

If you add a transmitter, well, the fact that you're listening via TV dongle obviously doesn't eliminate the licensing and equipment requirements for whatever radio service you're operating in, so a warning specific to this case is unneeded. Anyone "freebanding" or otherwise operating illegally probably knows exactly what they're doing, and if they don't care about what the law says, I very much doubt they care what you say either.

Re:better get

[fuzzyfuzzyfungus]

The widgets with this chip are all designed as TV-receiver USB widgets. I'm sure that there are some $11 electronics out there that are... um... totally FCC part 15 compliant; but no intentional radiating is going on.

Challenge Accepted

[Gordonjcp]

In a conventional radio receiver, you start by filtering off the wanted signal with a broad filter, mixing it with another locally-generated signal (the Local Oscillator) to make a lower Intermediate Frequency (IF), then filtering the IF to extract a single "channel" of information. Then you demodulate this, possibly after mixing it down to an even lower IF.

In a software-defined radio, you convert directly down to a much lower frequency (audio frequency, even), but - and this is the clever bit - you do it with two local oscillators, 90 degrees out of phase. This gives you a complex sample, a pair of samples representing In-phase and Quadrature, or the real and imaginary components of your signal.

From there you can apply digital signal processing techniques to extract the wanted signal, show an FFT of the chunk of band you're capturing, and so on. This lets you do very sharp filtering, because you're no longer constrained by the physical realities of trying to implement electronic filters with practical components.

Shameless plug - if you want to try SDR out, go here:
https://github.com/gordonjcp/lysdr
Follow the instructions in the README, then either post a reply or bug me in irc.freenode.net ##electronics for further instructions.

Re:Challenge Accepted

[YoopDaDum]

What you described is the difference between an old two stages RF architecture going from the target frequency to a base band signal through an intermediate frequency and a direct conversion / zero IF RF architecture. All recent RF chips for wireless are zero IF nowadays.

But SDR usually refers to the digital processing part. Some modem implementations use custom digital logic to do the processing. A SDR approach will use a big DSP (vector DSP even) to do the processing in software. Although typically some heavy parts like the FEC and FFT (for OFDM/OFDMA) can still be done with custom hardware for better efficiency.

In any case, the dream of a purely generic hardware is still only a dream. We can have flexible software modem (if you're not too concerned about die size and power efficiency), we have also wide band radios. But in front of that you still require a RF front-end (FE), comprising filters (not to be blinded by adjacent channels in Rx, or not to kill adjacent channels in Tx) and power amplifier in the transmission side. And there's no much flexibility there. You can have wide-band PAs, but it's limited and efficiency will suffer (so burn more power, heat more than a narrow band PA). And filters are not configurable. If you want to support many bands combinations, you end up with many different filters and a switch.

So the post is too optimistic. You may be able to toy a bit with this hardware, but don't expect making anything solid (product quality) based on that. Still for hacking and the fun / learning value, why not?

Re:Challenge Accepted

[pakar]

You should probably do a bit more fact-checking before saying stuff like that..

http://www.linuxfordevices.com/c/a/News/Embedded-Linux-powers-first-handheld-software-radio/
http://www.electronicsweekly.com/Articles/17/12/2007/42781/intel-targets-wimax-with-software-radio-device.htm

There are already chips that do direct-if conversion for DVB-T.. It's not a generic chip they use but a specialized that will have a high-speed ADC and then have hardware that do the 'tuning' to the wanted frequency...

So... There is stuff already doing this on a large scale...

If you want something that works with any type of protocol then you need some type of generic CPU that can be loaded with software that can be reprogrammed, and this is probable something that don't exist outside some specific circles, but it do exist and is available commercially. This stuff is usually done on FPGA's to reduce the powerusage and get good performance....

Re:Challenge Accepted

[colsandurz45]

All recent RF chips for wireless are zero IF nowadays.

Not true, super heterodyne is still very popular.

A SDR approach will use a big DSP (vector DSP even) to do the processing in software.

Not really. Depending on your platform the industry trend is actually going away from DSPs. DSP operations are being implemented in FPGAs these days (since they're faster and the newer Virtex 6 or 7s (and whatever Stratix whatever) are really huge).

subreddit dedicated to the RTL-SDR project

[citizenr]

http://www.reddit.com/r/RTLSDR

has all the info, list of tuners that work, tutorials and more.

Been there, done that

[ctrl-alt-canc]

A few years ago, together with a friend, we reverse engineered a DVB-T usb pen by Hauppauge, and we were able to extract the raw data stream skipping the demodulation process. We did it since we wanted to test if it the device could be used as a DSP IF strip in a homemade spectrum analyzer. The device worked, but the analog IF strip we wanted to replace was actually drawing circles around its digital replacement, so we abandoned the project. 8 bit of resolution and an hardware designed for a very specific purpose couldn't bring us too far, as we feared.
It is nice to see that somebody else was capable to reverse engineer these devices, but as you can see from their results, they aren't actually that good. I saw somewhere that a USB pen for DVB had to hit the market, and its ADC has been announced to be 12 bit wide.This could be an interesting device to hack for SDR applications, hoping it isn't vaporware...

Re:knowing he did that with an 11 dollar TV card

[Anonymous Coward]

You realize that if a significantly-sized company is selling you a radio for $1K that has $150 worth of parts in it, for an item that isn't mass-market consumer
    (and ICOM/Kenwood/Yaesu radios intended for the HAM market aren't "mass market", compared to, for example, cell phones), that they are on the edge of
    *losing money*. I've run two different manufacturing businesses in the last 20 years, and really, if you only look at the raw BOM costs of something, and don't
    factor in all the other costs of bringing a reliable product to market, you'll go out of business.

Many of the so-called "high dollar" SDRs out there are "high dollar" for fairly good reasons. They are typically sold into markets where economies of manufacturing scale don't really apply, they often have feature sets that are *vastly* larger than what we're seeing in these "rtl-sdr" devices, and they tend to use higher-quality components. These DVB-T devices, for example, use a master clock that is good to about 100PPM--which for radios is rather seriously crappy. They won't have features like a DDC (usually FPGA resident) for fine-tuning the RX signal. The 8-bit resolution may be fine for some applications, but for others requiring higher dynamic range, that 8-bit resolution will be a killer. Plus many of the "high dollar" SDR devices offer TX chains as well as RX chains, and all the other comments apply for the TX chain as well.

But one of the big things about "high dollar" SDR devices is that they're primarily designed as *development platforms* for developing SDR applications across a wide "spectrum" of fields of endeavour. So they include large FPGAs, those FPGAs allow you to perform part/all of your DSP algorithms at insane speeds inside the FPGA--speeds/sample-rates that would be impractical for a host-software implementation. Large/fast FPGAs are expensive, and that cost has to be passed on. Further, the "high dollar" SDRs typically offer bandwidths into/out-of the host at much higher sample rates than 3.2Msps. Yes, 3.2Msps, RX-only, 8-bit resolution, no-fancy features is entirely-adequate for a lot of different hobbyist work. But it's inadequate for a lot of other types of work for which the so-called "high dollar" SDRs are supremely-well suited.

Re:better get

[MichaelSmith]

> The FCC put rules into place a long time ago forcing manufacturers of receivers to block analog cellular frequencies from being received by the tuner

Do those frequencies seriously exist where you live? They were closed ten years ago here in Australia.

Re:knowing he did that with an 11 dollar TV card

[Anonymous Coward]

Jesus tapdancing christ, a finished product is more than the sum of its parts - you sound like the people who whine because Apple's making $x "profit" based on $sale_price - $parts_price.

1) Much higher quality hardware filters for the band and for the particular AF signal required, giving the sort of selectivity needed for amateur levels of power;
2) Low noise amps, again essential for amateur levels;
3) DDS or PLL tuners accurate to a few Hz at worst, not ones which vary by at least 100Hz on the tuned frequency;
4) Well-documented open or semi-open RS232/USB interface;
5) Higher resolution ADC;
6) DSP running on-board rather than wasting the CPU cycles of your far hotter desktop/laptop;
7) Good, local vendor support for a small market keen to get the most use out of a well-built product, rather than zero vendor support for a consumer market buying a throwaway item;
8) Sometimes an on-board UI.

Finally, you're ignoring that "Icom etc" make transceivers, whereas this is firmly receiver-only. And a shitty receiver is one thing, but someone operating a transmitter with shitty parts isn't only being a dick to fellow spectrum users but may be breaking the law.

eBay

[ArchieBunker]

But the sellers have sold out days ago along with all the other retailers. Looks like one is left and they ship direct from Hong Kong so expect a few weeks wait. I'm kinda pissed about only finding out now.

I've been toying with the idea of getting an entry level SDR for a while just to see what all is out there on the airwaves. This USB tuner chip appears to do the same thing as the $100+ Funcube Dongle.

Ask Slashdot: Mesh Networks?

[Bob9113]

Help a noob out; I'm just poking around on Wikipedia reading about SDRs and software defined antennas. These sound kind of like a magic pill to solve decentralized mesh networking. Stick an SDA on the roof, wire it up to an SDR, seek some marker signal identifying a freenet mesh node, focus in directional point-to-point comm to anyone in range who is running a compatible sda/sdr/router.

Does that about sum it up, or am I just being an over-excited noob?

Re:Ask Slashdot: Mesh Networks?

[Anonymous Coward]

AMPRnet has been around since the late '70s, various forms of packet radio existing before and after. The first TCP/IP stack I ever used was KA9Q.

1) lack of bandwidth;
2) legality of high power transmissions for non-hams;
3) legality of encrypted transmissions for hams.

"Radio" defined

[tepples]

there's still internet on radio. So what really is SDR useful for? For the common user -- and I understand this would require some bureaucracy -- mp3/ogg streaming over normal SW might be enough.

Perhaps you misunderstand what "radio" means. It's much broader than just "transmissions of popular music using frequency modulation in the 88.0 to 108.0 MHz band". See Grieviant's comment.

Re:better get

[pla]

Don't worry, friend - I only broadcast using 45KV sparkgap, not some wussy soft-tunable USB dongle.

GNU Source block code and ExtIO plugin for Windows

[balint256]

Hi folks,

If you want to start using the USB stick for SDR, please check out the follow options:

GNU Radio Source block 'rtl_source_c' in 'gr-baz' module: http://wiki.spench.net/wiki/gr-baz#rtl_source_c
Demo video: http://www.youtube.com/watch?v=FUQd9HOVTk8

ExtIO plugin for Winrad/HDSDR/WRplus: http://wiki.spench.net/wiki/USRP_Interfaces (grab the beta)
Demo video/install guide: http://www.youtube.com/watch?v=Z0hEquzLsWU

Let me know how you go!

Wrong link?

[Ozoner]

I think he posted the wrong link.

Perhaps he meant this one
"$20 ultra-cheap Software Defined Radio with RTL2832 DVB-T USB stick"

at http://www.youtube.com/watch?v=Z0hEquzLsWU

The original article is at
http://sdr.osmocom.org/trac/wiki/rtl-sdr

Re:Wikipedia the online encyclopedia

[Guy Harris]

"I found this great new site you may be unaware of. It's called Wikipedia. It is kinda of like an online encyclopedia that has brief summaries of almost anything", trout007 Is this the same Wikipedia that says Windows NT wasn't designed for the Internet?

No, it's the same Wikipedia that says

Consumer versions of Windows were originally designed for ease-of-use on a single-user PC without a network connection, and did not have security features built in from the outset. However, Windows NT and its successors are designed for security (including on a network) and multi-user PCs, but were not initially designed with Internet security in mind as much, since, when it was first developed in the early 1990s, Internet use was less prevalent.

which is not the same as "Windows NT wasn't designed for the Internet".

Re:better get

[maxwell demon]

Some interesting quotes from that article:

Four days later a gleeful letter confessing to the hack was printed by The Times. The writer justified his actions on the grounds of the security holes it revealed for the public good.

But, as author Sungook Hong relates in the book Wireless, his ambitions were frustrated by Marconi's broad patents, leaving him embittered towards the Italian.

Hackers disclosing security flaws, people hampered by broad patents ... seems the times haven't changed as much as we might believe!