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Author Topic: $20 USB Dongle SDR Receiver  (Read 132233 times)
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ta3as
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« on: July 24, 2012, 07:10:27 19:10 »

DVB-T dongles 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.
Dongles that use the Elonics E4000 offer the widest possible range (64 - 1700 MHz with a gap from approx. 1100 - 1250 MHz). When used out-of-spec, a tuning range of approx. 50 MHz - 2.2 GHz is possible (with gap).

It is now possible to listen to:

  • FM: both narrow band and wideband. (stereo FM too!!!)
  • AM:
  • Upper/Lower Sideband (USB/LSB).
  • CW: Continuous wave for morse code enthusiasts.
  • GPS reception:
  • Satellite reception including receiving ham transmissions from the International Space Station are possible to.

With GNURadio you can receive and demodulate digital modes such as pagers (POCSAG), ADS-B (aircraft positions), AIS (ship positions), AP25 and TETRA (digital trunk radio) and many others.
A USD 20 device is all thatís needed for receiving signals.

Regards,
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bobcat1
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« Reply #1 on: July 28, 2012, 10:38:53 10:38 »

HI

Sound interesting

Where to buy this type of device?

Bobi
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metal
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« Reply #2 on: July 28, 2012, 01:17:57 13:17 »

TBO, I am wondering about the quality?
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LabVIEWguru
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« Reply #3 on: July 28, 2012, 03:38:45 15:38 »

http://sdr.osmocom.org/trac/wiki/Hardware
http://sdr.osmocom.org/trac/wiki/rtl-sdr

http://sdrspace.com/
This is an access point of people that have their SDR connected to the internet. (If you were referring to reception quality) the ability to receive is incredible.

It is very cool to be able to "see" and hear your signal from different parts of the world. I was working with DDS to ultimately build my own SDR because of the cost of the commercial units (about $500 USD) but I have heard people are buying these up as fast as they can make them. People are using them for SAT-TV (with a down converter, I suppose)
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metal
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« Reply #4 on: July 28, 2012, 03:47:39 15:47 »

sorry, but what is "down converter" used for?
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LabVIEWguru
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« Reply #5 on: July 28, 2012, 04:48:49 16:48 »

Very high frequency signals are difficult to work with - requires precision expensive components and very expensive cable to bring the signal in to your bench and you still lose most of the signal. So, right at the antenna you amplify the signal and mix it with another signal (result is Hi frequency + mixer frequency, Hi frequency - mixer frequency) so then you use the lower frequency component because it is easier to experiment with.

A few years ago here in the US they passed a law that you couldn't make a radio that would receive some frequencies. Manufacturers programmed radios that "blocked" those frequencies. Some people got out their soldering irons and made a board (receive RF amplifier + mixer + oscillator) = blocked frequencies / 2 = a unused portion of most scanner radios.

Most people never cared to listen until the politicians said "you can't listen to that" then everyone started listening.
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CocaCola
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« Reply #6 on: July 29, 2012, 05:20:20 05:20 »

Where to buy this type of device?

The no brains way is to just hit up Ebay and search for 'Realtek RTL2832U' or 'Elonics E4000'

Retailers like Amazon.com have them, again search 'Realtek RTL2832U' or 'Elonics E4000'

As well as most of the larger 'Asian' based "We have everything in cheap electronics!" companies will have them as well, again search for 'Realtek RTL2832U' or 'Elonics E4000'
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ta3as
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« Reply #7 on: July 29, 2012, 01:50:32 13:50 »

sorry, but what is "down converter" used for?
Hi @metal,
These USB TV sticks have two chips generally. One is Elonics E4000 TV Tuner. It is capable to receive 64 mhz to 1700 mhz (with minor gaps approx. 1100-1250 mhz). So there is no need to use "downconverter" at this frequency range. This TV tuner chip uses zero IF architecture.

Regards,
 


Posted on: July 29, 2012, 01:06:52 13:06 - Automerged

Hi @metal,
I'm attaching  E4000 TV Tuner's internal diagram.

Regards,


Posted on: July 29, 2012, 01:42:11 13:42 - Automerged

HI

Sound interesting

Where to buy this type of device?

Bobi
Hi @bobcat1,
I'm using USB TV Tuners which have Elonics E4000 and Realtek RTL2832U chip.
I'm attaching a picture that I'm using.

Regards,

« Last Edit: July 29, 2012, 02:03:55 14:03 by ta3as » Logged
LabVIEWguru
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« Reply #8 on: July 29, 2012, 03:29:41 15:29 »

That is very interesting. What type of antenna do you use - probably a small dish? Is there a Low Noise Amplifier and downconverter at the dish? It is just incredible they are doing this in a USB dongle. Do you know what "zero if" is? Do they mean like a "no conversion" receiver? ..... infinite bandwidth, (almost) infinite response. I haven't looked into this yet, but do you know why there is a gap in the receive frequency? Is this a design restriction or because of the US restriction on receiving cellular frequencies?

I see the pics OK also

(later) I just checked Ebay and there are possibly 20 vendors - all in the 20 - 30 US Dollar range. The antenna is a small "whip" antenna - some even had a remote.

Very cool ta3as for bringing this up! This looks like a new toy!

One more question - are the units you show potted or can you remove the case and have access to the PC board and components? The unit like yours shown on Ebay looks like it just snaps apart.
« Last Edit: July 29, 2012, 04:10:14 16:10 by LabVIEWguru » Logged
ta3as
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« Reply #9 on: July 29, 2012, 04:14:52 16:14 »

That is very interesting. What type of antenna do you use - probably a small dish? Is there a Low Noise Amplifier and downconverter at the dish? It is just incredible they are doing this in a USB dongle. Do you know what "zero if" is? Do they mean like a "no conversion" receiver? ..... infinite bandwidth, (almost) infinite response. I haven't looked into this yet, but do you know why there is a gap in the receive frequency? Is this a design restriction or because of the US restriction on receiving cellular frequencies?

I see the pics OK also
Hi @LabVIEWguru,
I have two antennas. One is Diamond X50 ( http://www.diamondantenna.net/x50a.html ). It is a dual band antenna and it is working on 144 and 440 mhz. The other is ICOM AH-7000. It is a discone antenna which has wide coverage. AH-7000 discone antenna covers 25 mhz to 1300 mhz. ( http://www.eham.net/reviews/detail/985 )
There is no dish, there is no downconverter. I'm connecting my discone or dual band antenna directly to USB TV receiver stick. That's it :-))
USB TV receiver stick comes with a small antenna. You can listen a lot of stations with it but it's performance is not good so I'm preffering to use an external antenna.
USB TV stick's performance is good enough while using it with an external antenna. But you can add LNA ("Low Noise Amplifier") for better reception. At this time, it is enough for me working with an external antenna.
This is a real SDR (Software Defined Radio) A software-defined radio system, or SDR, is a radio communication system where components that have been typically implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented by means of software on a personal computer. So they are called "Zero IF"
What you thought 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.
I don't know why there is a small gap exactly. But I'm sure it is a technical restriction. Because this frequency range is not a blocked range in US or not a GSM frequency.
I hope I could answer your questions.

Regards,
PS: I'm attaching some screen captures. You can see FM broadcast activity at first picture and you can see 70cm (440 mhz) amateur band activity at second picture. As you can see you can monitor 2 mhz bandwidth. It is amazing.



« Last Edit: July 29, 2012, 04:37:08 16:37 by ta3as » Logged
metal
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« Reply #10 on: July 29, 2012, 04:46:02 16:46 »

This is really convincing indeed. The problem is that you will have to use a good quality antenna. I used FM radio cards in the past, you a re right, quality was poor till I used an FM antenna I bought from radio shack.
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DreamCat
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« Reply #11 on: July 29, 2012, 05:43:47 17:43 »

I already have a plan to buy one, just about 76 yuan. but I really want to build a low frequency SDR, employ the analog Switch/Multiplexer as Phase Detector I/Q....
once I done the work, I will start paly them. Grin
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May be I expressed the wrong meaning, sorry for my bad english. Please correct it for me if you can.
ta3as
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« Reply #12 on: July 29, 2012, 05:47:58 17:47 »

This is really convincing indeed. The problem is that you will have to use a good quality antenna. I used FM radio cards in the past, you a re right, quality was poor till I used an FM antenna I bought from radio shack.
You are right. You need good antenna and good coax transmission line for better reception.
BTW, I think this topic is a real "project" which combines RF electronics and computer. So is it possible to re- move this topic to "projects" section?  I'm planning to write some hardware mods about this usb stick.
Thanks...
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metal
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« Reply #13 on: July 29, 2012, 06:32:15 18:32 »

Project moved ta3as.
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ta3as
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« Reply #14 on: July 29, 2012, 06:49:48 18:49 »

Hi,
Elonics E4000 tuner can tune 64mhz to 1700 mhz. What about below 60 mhz?
There is a modification now. You can solder a longwire antenna for SW (shortwave) reception to pin 1 of the RTL2832U chip.
Now you can receive DC to 30 mhz.   Wink This is direct sampling mode modification of USB TV dongle.
No downconverter plugged in. Wire is directly soldered to pin 1 of RTL2832
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solutions
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« Reply #15 on: July 29, 2012, 11:03:25 23:03 »

GPS L2 falls into the gap at 1227.60 MHz.  Looks like it's aviation nav (see attached chart clipping), though the stuff I'm used to for aircraft is at 1xx MHz - some of the gap is TACAN at 960-1215 MHz, though I'm not sure why the Chinese would care about blocking it.

A nice USA frequency allocation (2003, so maybe a bit dated) chart here:  www.ntia.doc.gov/files/ntia/publications/2003-allochrt.pdf
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« Reply #16 on: July 29, 2012, 11:12:23 23:12 »

Fascinating.  I previously owned an Icom PCR1000 that was a $1000.00 device with about the same capabilities.

I just ordered "Realtek RTL2832U & Elonics E4000-Based USB DVB-T Receiver..." via eBay $27.00, will be fun!
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ta3as
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« Reply #17 on: July 29, 2012, 11:16:50 23:16 »

GPS L2 falls into the gap at 1227.60 MHz.  Looks like it's aviation nav (see attached chart clipping), though the stuff I'm used to for aircraft is at 1xx MHz - some of the gap is TACAN at 960-1215 MHz, though I'm not sure why the Chinese would care about blocking it.

A nice USA frequency allocation (2003, so maybe a bit dated) chart here:  www.ntia.doc.gov/files/ntia/publications/2003-allochrt.pdf
Hi @solutions,
Thanks for the chart. Tuner chip (Elonics E4000) designed in UK so I don't think that the Chinese blocked it.

Regards
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borberk
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« Reply #18 on: July 29, 2012, 11:58:37 23:58 »

First pins on RTL2832U are 1. I+, 2. I-, 4. Q+ and 5. Q- inputs. Normally they are connected to E4000 I and Q outputs through 100nF capacitors.
Reference schematics for E4000 is here superkuh.com/gnuradio/e4000_refsch_rev4.pdf
« Last Edit: July 30, 2012, 12:18:21 00:18 by borberk » Logged
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« Reply #19 on: July 30, 2012, 02:31:51 02:31 »

http://www.ct1ffu.com/site/index.php?option=com_content&view=article&id=178:coverter&catid=38:artigos

Very nice upconverter - allows receiving from DC to 1700 Mhz

-----------------------------------------------------------------------------------------------------

Seems some people have damaged their SDR dongles because the E4000 was missing a protection diode on the input:

"They have BAV99 (labelled A7t) for ESD protection on the antenna input, so there is less need to worry about burning out your tuner than with other cut-rate devices."
------------------------------------------------------------------------------------------------------
http://sdr.osmocom.org/trac/wiki/rtl-sdr

Apparently THE site for dongle SDR
---------------------------------------------------------------------------------------------------------
http://www.reddit.com/r/RTLSDR/

very recent Discussion threads
---------------------------------------------------------------------------------------------------------
If you are in the US, I would carefully consider admission that you listen to cellular or decode POSAG transmissions. This was made a federal crime a few years ago.
--------------------------------------------


Ta3as - can you recommend any really useful sites?
« Last Edit: July 30, 2012, 02:42:23 02:42 by LabVIEWguru » Logged
solutions
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« Reply #20 on: July 30, 2012, 04:16:11 04:16 »

---------------------------------------------------------------------------------------------------------
If you are in the US, I would carefully consider admission that you listen to cellular or decode POSAG transmissions. This was made a federal crime a few years ago.
--------------------------------------------

I think, in the past two years or so, listening in on cellphones and snooping emails has become "legal" in the US. If the Feds can do it without a warrant, you can, IMO.

So, the discussions went from Realtek (Taiwanese) to Elonics. If Elonics has the wider range, why bother with Realtek at all?

@Borberk - thanks for the schematic and picture - I find it amazing that they are hand soldering those boards....
« Last Edit: July 30, 2012, 04:26:00 04:26 by solutions » Logged
borberk
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« Reply #21 on: July 30, 2012, 06:32:25 06:32 »

@solutions, Realtek product RTL2832U is DVB-T demodulator. It accepts I and Q signals coming from tuner E4000, EC0012 or EC0013. Receive bandwidth depends only on type of tuner and they all are Elonic products. Both parts are essential and do not mix them.

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ta3as
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« Reply #22 on: July 30, 2012, 05:05:48 17:05 »

Ta3as - can you recommend any really useful sites?
Hi @LabVIEWguru,
I'm running SDR#  ( http://www.sdrsharp.com/ ) for receiving and controlling the USB TV stick.
This page ( http://rtlsdr.org/softwarewindows ) explains the installation step by step.
This is the another interesting web page. ( http://www.rtlsdr.com/ ) Users are sharing their experiences. There are a lot of videos.
You can run "Release of K5DEV SDRSharp Fork" if you want to add "scanner" and " frequency manager" facility to SDR#. ( http://www.k5dev.com/ )
I'll add some site address for decoding digital transmissions such as AIS, ADS-B, RTTY,TRUNK....

Regards,
 
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Cain
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« Reply #23 on: July 30, 2012, 06:37:44 18:37 »

I'm running SDR#  ( http://www.sdrsharp.com/ ) for receiving and controlling the USB TV stick.

Interesting topic and I've had a ezcap on laying my desk for some months so now it's the time to get it up running!

Tried to download the program from link above but looks like the version available no longer have "RTL2832U / RTLSDR" support. What version are you using and where to find a version that support RTL2832U?

Thanks in advance!
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ta3as
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« Reply #24 on: July 30, 2012, 08:10:35 20:10 »

Elonics E4000 white paper Please see attached text file.

Posted on: July 30, 2012, 08:06:05 20:06 - Automerged

Interesting topic and I've had a ezcap on laying my desk for some months so now it's the time to get it up running!

Tried to download the program from link above but looks like the version available no longer have "RTL2832U / RTLSDR" support. What version are you using and where to find a version that support RTL2832U?

Thanks in advance!
Please download sdr#dev not sdr#stable. SDR#dev  (build 514) has RTL2832U support. Please let me know if you have any installation problems.

Regards,
« Last Edit: July 30, 2012, 09:15:41 21:15 by ta3as » Logged
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