2013-06-17

Naked hardware #11: unbranded RTL2832U + R820T

RTL2832U + R820T bulk DTV stick teardown

That stick is Realtek RTL2832U reference design with Rafael Micro R820T RF tuner . USB ID is 0bda:2832, which is chipset default reference design ID. Why there is still eeprom?

Linux support has been added since the Kernel 3.10.

unbranded RTL2832U + R820T

unbranded RTL2832U + R820T stick

Key components:

Realtek RTL2832U
Rafael Micro R820T

Hardware internals

RTL2832U + R820T stick PCB

All components are assembled to that side of the PCB. Very standard RTL2832U stuff with nothing extra. Main components from left to right are: power LED, IR-receiver, MCX antenna connector, A7 - BAV99 diode, R820T RF tuner, 28.800 MHz crystal, 24C02 serial eeprom, RTL2832U DVB-T USB interface + demodulator, FS1117 voltage regulator and type A USB connector.

28.800 MHz clock is shared with RTL2832U and R820T - saving one component. BAV99 diode is used for ESD protection. It protects RF tuner possible ESD coming from antenna connector. RTL2832U devices having that RF tuner are very popular currently, especially in SDR usage.

There is not much to explain as I have already teardowned two devices build upon RTL2832U, but having different RF tuner. Look these first:
Naked hardware #6: ezcap USB 2.0 DVB-T Stick
Naked hardware #7: TerraTec Cinergy T Stick Black

R820T RF tuner

That RF tuner is quite new as it appeared devices less than one year ago. It is the latest tuner added to the RTL2832U reference designs until now (what I know).

Tuner is designed for digital terrestrial standards. Frequency range is from 42 to 1002 MHz, but it is said to to perform far more over that. Wide frequency range makes this tuner interesting, otherwise it is rather similar than typical DTV RF tuners nowadays. Everything but crystal is integrated, which mean less external components. No need for external LNA nor SAW filters (SAW filters are not needed since 1st generation silicon RF tuners, QT1010, MT2060, etc.).

R820T differs from the trend seen during last few years as it is not direct conversion aka zero IF tuner. That tuner is so called low-IF tuner, which means it uses intermediate frequency (IF) 5 MHz or less. Over the years, IFs used by DTV tuners has gone down from the ~50 MHz to few MHz or even zero (baseband). Compared to traditional superheterodyne architecture, direct conversion has many advantages like simpler architecture, lower power consumption and no harmful image frequency. Whilst direct conversion has many advantages it has some disadvantages too, most notable DC offset.

R820T power consumption

As this RF tuner has different architecture than all the other modern tuners used with the RTL2832U I decided to take some measurements to see how much more power it consumes than those which are based of direct conversion architecture. I used live 634 MHz DVB-T signal which has 8MHz bandwidth. That is very typical DVB-T transmission condition.

Here are the results, measured from the USB, nominal voltage 5V:
fc2580: 183mA
e4000: 176mA
fc0012: 166mA
tua9001: 186mA
r820t: 313mA

Architecture complexity has a price. It seems to drain around 135mA more current than Zero-IF tuners compared. I could assume it is pretty much same for all the the other low-IF tuners too that are designed during last 3 years or so.

PCB bottom side is empty

a lot of room for components
There is not much to say from that side of PCB. Few wires and two hole arrays, under the RTL2832U and R820T chips located other side. Those are for cooling. That device has a lot of empty room :)

USB interface

IDLE current drain without a driver: 110mA



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10 comments:

  1. I have one of these. I am using SDRsharp S/W
    It clearly has a dc offset. About -200uV on both I and Q channels.
    Why is this?
    This chipset is meant to use a low IF rather than zero IF.
    Could it be that SDRsharp is not configuring the down conversion frequency correctly.
    I know the offset voltage from looking at recorded time domain data having calibrated with a known amplitude signal.
    When I look at the data in the time domain I can see the dc offset.
    (Also, when I look at the spectrum in SDRsharp the dc spike appears at about +47.6kHz which is weird. I have no frequency offsets set.)

    O

    ReplyDelete
  2. I have one of these on order. I am looking to put it in an enclosure. Any chance you could publish dimensions of the PCB?

    ReplyDelete
    Replies
    1. Device case is very easy to open. Usually you will break some brackets when opening such device, but that one opens without any damage.

      78.5 * 25.0 mm. Whole device. Including USB-connector and antenna connector, but without case.

      63.2 * 22.1 mm. PCB only. That is dimensions of plain PCB. Imagine it like all components are removed.

      Maximum thickness is 9.3 mm. It is measured from only LED visible.

      Delete
  3. Do you guys know if this dongle works with linux ?

    ReplyDelete
    Replies
    1. Yes it works.
      " Linux support has been added since the Kernel 3.10."

      Delete
  4. This comment has been removed by the author.

    ReplyDelete
  5. I have just a small problem with this one. SDR# works great and so othe rprograms, but I also wish to use the infrared receiver. Blazedvd works (with original drivers) but I can't seem to get IR keys/data from any other program. Any clues?

    ReplyDelete
    Replies
    1. Remote controller should be work, but I haven't tested it still. Remote controller keytable is not load automatically as device uses chipset default USB ID and due to that it is impossible to map correct keytable (many different devices and remote controllers used by same ID). So you have to load keytable manually. That remote controller looks very popular, there is likely correct keytable already, but I don't know name :-)

      ir-keytable
      Found /sys/class/rc/rc0/ (/dev/input/event16) with:
      Driver dvb_usb_rtl28xxu, table rc-empty
      Supported protocols: NEC RC-5 RC-6 JVC SONY SANYO LIRC other
      Enabled protocols: NEC RC-5 RC-6 JVC SONY SANYO LIRC other
      Name: Realtek RTL2832U reference desig
      bus: 3, vendor/product: 0bda:2832, version: 0x0100
      Repeat delay = 500 ms, repeat period = 125 ms

      Could someone else point command to load correct keytable for this device?

      Delete
    2. Hello,

      I have a problem with usb tunner RTL2832u R820T, ID 0bda:2832 .

      Problem is in the read signal and quality with femon.

      Ubuntu 14.04, kernel 3.13.

      Femon out:

      Problem retrieving frontend information: Operation not supported
      status SCVYL | signal 0% | snr 0% | ber 0 | unc 1 | FE_HAS_LOCK

      Tunner testing with Ubuntu 12.04, kernel 3.2 with driver from:

      http://linbay.blogspot.cz/2012/05/hassle-almost-free-rtl2832u-linux.html

      files: http://upload.hidemyass.com/files/L7xsZ/

      femon out:

      Problem retrieving frontend information: Operation not supported
      status SCVYL | signal 40% | snr 100% | ber 0 | unc 1 | FE_HAS_LOCK


      Please fix the driver for rtl2832 in media_tree.

      Thanks

      Delete