With a simple digital TV USB capture card, you can build your own software defined radio or spectrum analyzer. While it may not be as cool as [Jeri Ellsworth]’s SDR, it’s still very useful and only requires $20 in hardware.
The only piece of hardware required for this build is a USB FM/DTV capture device with the Realtek RTL2832U chipset. So far, two USB sticks have been tested and the unit with the largest frequency range (64 – 1700 MHz) is available direct from China for $20.
Turning these cheap capture cards into software defined radios and spectrum analyzers was discovered by [Antti Palosaari] after sniffing the device. These cards demodulate the frequency and send all the data to the computer and is decoded via software. If you have one of these capture cards lying around, you can grab the software and load it up on your *nix box. Right now, the software only writes directly to a file, and may drop a few samples if writing to a hard disk instead of ram. Small problems, but we’re sure this project will pick up steam in the very near future.
via reddit
So… Its the same concept as the Funcube Dongle and seems to use the exact same chip?
@Neckbeard It looks like the same front end, but the FunCube appears to use USB sound card hardware to do the sampling. FunCube website says ~96KHz I/Q, whereas according to the SDR thread, the sample rate in the example was 2.048 MHz. It would have to have a faster ADC to handle video data rates. This also explains why the FunCube is driverless, and this thing is going to require more hacking to make a useful driver.
Wow, this beats the pants off the price of the Funcube Dongle though!
/me excited
You have a broken link there(direct from China).
Cursed WordPress.
Just search dealextreme for “DVB-T Digital TV USB Dongle Stick With FM/DAB/DAB+” It’s $19.50 USD with free shipping, about 16 euros. SKU = 44326.
This was the link they tried to put on there.
http://www.dealextreme.com/p/dvb-t-digital-tv-usb-dongle-stick-with-fm-dab-dab-44326
That would be the one.
A couple of comments:
1) The stick doesn’t have a preamplifier like the FDCP have => Sensitivity is clearly not as good
2) The stick only sends 8 bits IQ sample, so the dynamic range is pretty limited.
3) Beware that not all stick using the RTL2832 have a elonic E4000 tuner. Some have another models and those can be much more limited
4) While the availability of the raw mode was indeed discovered by Antti Palosaari while looking at a FM mode capture, it’s important to note that all the work for finding exactly how to exploit it and write the actual software was done by Steve Markgraf.
It doesn’t look like it would be difficult to add a preamplifier to the front end.
I have one designed here which could take the place of the RF connector: https://github.com/loxodes/rtl-sdr-lna
So does this decode the DVB-T streams in software, or just the FM radio stuff? I’d suspect it’s just FM radio stuff, but curious to know. I ordered one right away when I got the email for this post.
From the software’s webpage “rtl-sdr is a commandline tool that can initialize the RTL2832, tune to a given frequency, and record the I/Q-samples to a file.”
To understand I and Q, I would advise reading the following:
http://www.flex-radio.com/Data/Doc/qex1.pdf
http://www.flex-radio.com/Data/Doc/qex2.pdf
http://www.flex-radio.com/Data/Doc/qex3.pdf
http://www.flex-radio.com/Data/Doc/qex4.pdf
With the I/Q streams you can demodulate AM/FM/PM or hybrid combinations if you write the software based DSP to do the demodulation. Or if you use the software built by others already.
I do understand how SDR stuff works. Not down to the math of it, but I have several softrocks.
My question was more of, does this pass the IQ stream wide enough that the dvb-t is decoded in software or does it decode that itself and pass the bits to the computer?
The RTL2832U has a DVB-T demodulator in it so it just passes the MPEG multiplex and transport to the PC. In radio mode (the mode of interest here) it just passes the sampled IQ baseband to the PC for demodulation in software. The Windows application that comes with it has an FM and DAB+ demodulator in software. This is what makes it such a nice front end for GNURadio.
can this be sued with gnu radio? if so WANT!
for god sake, why does do I always need to click every link in the description for find the article
It’s always the first one*. Yes, there is a style guide for hackaday.
*except in rare cases where it’s obviously not. Such as “Blah blah this is a follow up to link. Now, there’s new build.”
Nice, I’ll try it this weekend with my DigiVox mini II V3.0 stick.
Gotta love it when you find out something cheap can be made useful with a little hacking.
I want this, but dealextreme is 3 weeks behind on my last order (ordered 2/26/12). Has anyone found a local source?
But CRDA restricts you to 5 nano watts of power and channels 5+6! the FCC is my lord and master
That’s funny, they have these licences that you can get that give you all sorts of privileges!
Also: WTF Hackaday!!! “That email address is associated with an existing WordPress.com (or Gravatar.com) account. Please click the back button in your browser and then log in to use it.”
Guys, bad news – they are out of stock at dealextreme, but you can still get them at aliexpress
It didn’t say they were out of stock when I checked
Dealextreme never shows updated stock information.
I canceled my order at dealextreme last night and placed one on aliexpress and it’s now sold out there.
Annoyingly, the seller didn’t process my order when it was still in stock as he saw I was in the USA which uses ATSC.
ETA “15-20 days” for aliexpress; “Who knows?!” for Dealextreme.
For those in Australia Catchoftheday and Zazz have the ezCap dongle for sale every few months.
where you able to get the ezcap to work ?
you can buy directly from easycap
http://www.usbeasycap.info/
and yeah WTF on login ..?
Better story link here: http://dangerousprototypes.com/2012/03/20/introducing-rtl-sdr-a-20-sdr/#comment-34722
I have a dongle and the receiver is quite weak. Even with a DVB transmitter only 5km away I don’t get a TV signal but I do get FM on it using the supplied little antenna.
A good and cheap 70MHz to 2GHz amplifier to go with the dongle might be this:
http://www.minikits.com.au/kits2.html#pha1
Now THIS is the stuff that should be on this site. Cool!
What do you think the odds are that the ATSC version (the one that would work with US TV) would have the same capabilities?
http://usbeasycap.com/index.php?main_page=product_free_shipping_info&cPath=5&products_id=65&zenid=1d4oaldtrfo2mj5u0sog1oa653
Unless you want to use the dongle to watch TV in the USA there is no need to buy an ATSC version – just get the DVB/DAB/FM one. The model I have is EZTV646 but the PCB is exactly the same as the one in the picture – including the EZTV668 1.1 text.
This is nowhere near as useful as the funcube due to the built in ADC converter. It is only 7-bit. You may be able to receive broadcast FM (which is the initial purpose of the device), but not good for much else the resolution is not there.
8, as in 8 bit. not 7.
And as it was already stated 8 bit is enough for fm, dab, dab+, tetra, gsm, gmr.
But hey, i’d certainly take more than 8 bit for 20$ any time…. feel free to suggest something.
Besides what James said, the consequence of having 8 bits versus 16 or 24 bits is that there is not as much dynamic range available (48 dB vs 96 dB and 144.5 dB, respectively). An adjustable preamplifier or attenuator can bring the received signal into the range handled by 8 bits. You can also utilize oversampling and decimation to increase the resolution, hence the dynamic range. For example, to increase the resolution from 8 to 11 bits, oversample the data at a rate 64 times that desired. If the sampling rate is 2,560,000 samples per second, the effective sample rate will be 40,000 samples per second, which is still a useful I&Q sample rate for SDR. There is plenty of information on oversampling and decimation available through Google, so I won’t go into the details here.
I have a broken DVB-T stick here.
Might try and fix it, IIRC it was
broken remote at the time.
The stick shows up but won’t install
and I can’t locate a driver.
Conundrum, you need a DAB stick, I have a DVB-T stick but the requirenent is for the wide band DAB output.
This seems to be moving very fast I’m ordering my DAB stick, an 8 bit 2MHz wide SDR for $20, yes please.
Found that the receiver chip can be used for GPS and I’m sure it’s wide enough for ADS-B, and of course polar orbit weather sats. These could be the handiest radio bits ever.
What about aviation (air) band, ~108 to 137MHz AM (not FM)?
I can confirmn the sticks indeed work well, get anymake, as long as it has the required chip sets.. It compliments the funcube very well
I use my stick for airband, SATs and FM broadcast reception. The available dll will work with Winrad, WR+, HDSDR etc Also works with GNU radio