RTL-SDR Blog V.3. Dongles User Guide

Version 3 of our customized RTL-SDR dongles brought out some new interesting features. In this guide we explain how to use those feature. If you are interested, we also have the V3 feature datasheet available here.

Feature 1: Direct Sampling HF Mode

This feature allows you to listen to HF signals between about 500 kHz to 28.8 MHz.

To use direct sampling mode

  1. Connect an appropriate HF antenna to the SMA antenna port (this is the same port where you connect your VHF/UHF antenna). 
  2. In SDR# select the Q-branch in the configure menu (the cog icon next to the play button). (If it is greyed out make sure you stop the SDR first, by clicking the stop button in SDR#)
  3. Press Play and tune to 500 kHz - 28.8 MHz.

Q-branch

VHF antennas like small discones or short whip antennas will probably not pick up HF signals very well, if at all. If you have one of our dipole antennas, try connecting a long 5 meter or longer wire to the element connected to the coax center wire. To check which element is connected to the center coax you can open the lid on the black dipole base. Ideally you should use a 9:1 unun with the long wire antenna for optimal reception. Even more ideally you'd use an antenna tuner, though this is expensive.

HDSDR/GQRX and Other Software

Other software like HDSDR and GQRX can also support direct sampling. It may entail setting a device string, and for the Q-branch, the value should be 2 (or sometimes 3). In GQRX the device string would be "rtl=0,direct_samp=2" (without the quotes). In some installs that use different drivers it may be "rtl=0,direct_samp=3" instead. Make sure that there is no space after the comma. For SDR-Console please see this linked post for a modified ExtIO that can enable direct sampling. SDR-Touch on Android has a direct sampling option available in its settings page.

To go back to listening to frequencies above 28.8 MHz remember to change the sampling mode back to "Quadrature Sampling".

Note that this feature makes use of direct sampling and so aliasing will occur. The RTL-SDR ADC samples at 28.8 MHz, thus you may see mirrors of strong signals from 0 - 14.4 MHz while tuning to 14.4 - 28.8 MHz and the other way around as well. To remove these images you need to use a low pass filter for 0 - 14.4 MHz, and a high pass filter for 14.4 - 28.8 MHz, or simply filter your band of interest. (Note that that 28.8 MHz is downsampled on chip resulting in the 3.2 MHz bandwidth)

Modified rtl_tcp for direct sampling

The standard Osmocom version of rtl_tcp only allows for direct sampling on the I-branch, which is useless as we need direct sampling on the Q-branch. Please see our RTL-SDR-Blog Drivers for a version that includes a -D direct sampling flag. The Releases page has a Windows release.

Forcing Direct Sampling To be Always ON

In some cases you may want to force direct sampling to be always on. For example, not all programs expose the direct sampling controls to the user, so in those programs it can be impossible to turn direct sampling mode on. To force it on, use our RTL-SDR-Blog driver branch, and use set the direct sampling always on flag in the EEPROM with the command "rtl_eeprom -q y". To disable forced direct sampling do the opposite command "rtl_eeprom -q n"

Feature 2: Software Selectable Bias Tee

V.1. and V.2. of our dongles included a bias tee which could manually be enabled by opening the case and soldering two pads on the PCB together. V.3. introduces a 4.5V bias tee that can be toggled entirely in software. The bias tee can continuously pull up to 180 mA of current.

WARNING: Before using the bias tee please ensure that you understand that you should not use this option when the dongle is connected directly to a DC short circuited antenna unless you are using an LNA. Although the bias tee circuit is dual protected against accidental shorts with a thermal self-resetting fuse and overcurrent protection on the LDO, short circuiting the bias tee for an extended period of time (days) could damage the LDO or fuse permanently. Only use it while connected to an actual powered device, like an LNA, active antenna or the SpyVerter.

To make things clearer: DC Short Antenna -> LNA -> Coax -> V3(bias tee on) is absolutely fine. What's not good and makes no sense anyway is DC Short Antenna -> Coax -> V3(bias tee on). DC Short Antenna -> Coax -> V3(bias tee off) is fine.

Note that the legacy DVB-T TV drivers will activate the bias tee by default. On Linux ensure that you have properly blacklisted the DVB-T drivers. More info on how to blacklist on the Linux section on the quickstart guide.

Optional Video: Bias tee tutorial by SignalsEverywhere available here.

To enable the bias tee in Windows:

  1. Download and extract all the files in this zip file to a folder on your PC. It contains two batch files that can be run.
  2. Make sure all SDR software like SDR#/HDSDR/SDR-Console etc is fully closed.
  3. Run the biastee_on.bat file to turn the bias tee on. It will run and open a CMD prompt that will briefly say "Found Rafael Micro R820T Tuner". The CMD prompt will close soon after upon success.
  4. The bias tee is now on. To turn it off repeat steps 2 & 3, but instead run the biastee_off.bat batch file. Alternatively, simply disconnect and then reconnect the SDR to turn the bias tee off.

If you have multiple dongles connected you'll need to edit the batch file to specify what dongle's bias tee you want to activate. Open the bat file with any text editor, like Notepad, and add the dongle selector "-d" flag. For example to activate the bias tee on the dongle that was plugged in second you'd need to change it to "rtl_biast -b 1 -d 1".

If you get a Smart Screen message, click on More Info, and then on Run Anyway. Also note that some versions of Windows may fail to run batch files due to misconfiguration or aggressive antivirus software. If you cannot fix these problems with Windows or your antivirus, run the command manually on the CMD line.

To run it manually on the CMD line first browse to the directory where the bias tee software is stored using "cd" (e.g. cd C:\SDR\bias_tee_folder), and then run:

  1. ON: rtl_biast -b 1
  2. OFF: rtl_biast -b 0
  3. If needed select a particular RTL-SDR device with the -d flag.

To enable the bias tee in Linux:

In Linux or MacOS download the source from git, compile it the same way you do the regular RTL-SDR drivers, and then run ./rtl_biast -b 1 to turn the bias tee on and ./rtl_biast -b 0 to turn the bias tee off. The procedure is:

git clone https://github.com/rtlsdrblog/rtl-sdr-blog
cd rtl-sdr-blog
mkdir build
cd build
cmake .. -DDETACH_KERNEL_DRIVER=ON
make
cd src
./rtl_biast -b 1

If you want to be able to run the bias tee program from anywhere on the command line you can also run "sudo make install".

If you have trouble running the bias tee check with a multimeter if there is 4.5V at the SMA port. Also check that your powered device is actually capable of receiving power. Remember that not all LNA's can accept bias tee power. We recommend Adam 9A4QV's LNA4ALL, as you can order this from his store with the bias tee power option enabled. If you need further help please contact us at [email protected]

Enabling the Bias Tee in PiAware

Please see this link for instructions, or see below to see how to force the bias tee to be always on.

Forcing the Bias Tee to be Always On

If you are using our RTL-SDR-Blog driver branch you can force the bias tee to be always on by setting a flag in the EEPROM. The rtl_eeprom command is "rtl_eeprom -b y". Run the opposite command "rtl_eeprom -b n" to disable the forced bias tee.

Feature 3: Selectable Clock & Expansion Headers

This is for advanced users who need to daisy chain clocks together for coherent experiments, or need to access other ports. You can either bridge the clock selector the directly with a solder bridge, or solder on a 1.27mm 2x2 header pin jumper.

To add a jumper to the CLK selector header.

  1. Carefully remove the 0 Ohm resistor.
  2. Very carefully solder a 1.27mm 2x2 header onto the clock selector pads.
  3. You can now select your clock input.

How to connect the CLK jumpers:

CLK_1

 The first position allows you to output the dongles clock to the CLK pads. The second position allows you to input an external clock.

CLK2

An example of CLK daisy chaining is shown below. One dongles TCXO is connected to two other dongles who have disconnected clocks.

CLK3

Feature 4: Additional GPIO Ports

Please see the guide written by Rodrigo Freire here.

LF/MF Improvement / Bias Tee Disable Mod:

If you want to improve the performance at LF/MF (below 500 kHz) and do not require the bias tee, then you can remove the bias tee inductor at L13. Of course remember that if you are interested in VLF/LF, it might be a better idea to use an upconverter like the SpyVerter, which can be powered by the bias tee on the dongle.

Notes to be aware of:

I opened my RTL-SDR V3 dongle and found that the thermal pad has a small air gap between it and the enclosure, is this normal?

This is normal. The purpose of the thermal pad is to fix L-band VCO lock problem that are related to PCB heat build up. The RTL-SDR V3 only requires very minor heat sinking to overcome this issue, and a small air gap does not reduce the thermal transfer enough to cause issues. In fact the V3 PCB has already been redesigned to dissipate heat better, so the thermal pad is not strictly required, except in very warm climates.

My RTL-SDR V3 is getting hot.

Please remember that these units do get hot to the touch especially when used in warm climates. This is not an issue and is normal. The temperature will normally be about 20 - 25C above ambient. We have improved the thermal bonding and heat transfer between the chips and the metal case. This results in making the metal case hotter, but it keeps the chips much cooler, resulting in better performance. To lengthen the life of the dongle we recommend keeping the unit away from direct hot sunlight.

Current Known Issues:

We're constantly trying to improve our units and we always make note of what issues exist and how to fix them.

2019 Onwards:

No known issues.

2019 and earlier units (no longer shipping):

Note that the following problem has been fixed in newer batches with a new design.

0.2 - 0.3% of units may have a faulty RTL2832U chip. This is characterized by higher than normal USB currents (normal is 0.28A - 0.3A), and often random disconnections from the USB as well as increased heat. The same problem affects all brands of RTL-SDR.

2018/8 Batch (no longer shipping):

A small number of these units (~approx 300 units) had faulty bias tee LDO chips which caused the bias tee to be permanently on. The cause was bad silicon in the LDO chip. These units run normally in all other ways, except that the bias tee cannot be turned off. They can continue to be used normally, without the bias tee. The thermal fuse will protect against short circuits.

If you have one of these, feel free to contact us at [email protected] for a replacement, or if the bias tee is not important to you and you can solder, removing the L13 inductor will fully disable the bias tee.  

Known V3 Batch 1 Issues (limited quantity batch, no longer shipping):

  1. Increased sideband noise on very strong narrowband signals. This should not be a significant problem as it only affects very strong signals. The hardware fix is to add about 100-220uF of capacitance on the 3.3V power line. Batch 2 will reduce this noise.
  2. The bias tee when turned on adds a large spur in direct sampling HF mode. This may be problematic only if you intend to use a bias tee powered HF LNA in direct sampling mode. This can be fixed by adding about 2.2uF of capacitance to the output of the LDO, before the inductor. Batch 2 will fix this.
  3. The bias tee can be damaged by accidentally short circuiting the output for a few seconds while it is on. This damage only occurs on USB3.0 and USB2.0 ports that can provide up to 1A or more or current. Batch 2 will add a resettable fuse to prevent damage.

 

Posted in

257 comments

  1. KD9MAP

    Thanks to Bertie for the quick replies! I got it working on HF again, although the gqrx device select menu still switches me back to device “Other” when I change the device string to ‘rtl=0,direct_samp=3’. Here’s what gqrx says when I change the string:

    gr-osmosdr 0.2.0.0 (0.2.0) gnuradio 3.8.1.0
    built-in source types: file osmosdr fcd rtl rtl_tcp uhd miri hackrf bladerf rfspace airspy airspyhf soapy redpitaya freesrp
    Using device #0 Realtek RTL2838UHIDIR SN: 00000001
    Found Rafael Micro R820T tuner
    [R82XX] PLL not locked!
    Enabled direct sampling mode, input 3

    To get gqrx working on HF again I did two things: upgraded to gqrx-2.14.4, and upgraded to the latest osmocom rtl-sdr drivers and tools. I built both from the git source packages. Probably it was the driver upgrade that fixed it.

    Thanks Again Folks!
    KD9MAP

  2. KD9MAP

    Hi! I’ve been using RTL-SDR v3 for a long time, for HF and VHF, using both SDRSharp on Win and gqrx on Linux Mint. All of a sudden gqrx won’t let me set direct_samp=3 anymore. If I do, it changes the device type to Other. If I try changing the device type back to “Realtek RTL2838…” then it removes the direct_samp=3 from the device string. Sometimes while I’m trying to configure it, gqrx crashes. I didn’t change anything with gqrx that I am aware of. I’ve tried gqrx 2.12 and 2.11.5. My dongles still work fine on HF with SDRSharp on Win10. Something got misconfigured on gqrx or linux I guess 🙁 Does anybody have any suggestions? Thanks Very Much! KD9MAP

  3. Yves

    Hello
    I have an sdr blog V3 since 3 years, i went in a new home a few weeks ago with 10 Kw FM emitter at 300 meters of home and 3 V/m field. The sdr has burn out on IQ , i have only spurs now. It works on Q branch only for HF.
    I think the protection is not enough, may be 2 diodes like rtlsdr key is better protection.

  4. Nicholas

    > Forcing the Bias Tee to be Always On
    >
    > If you are using our RTL-SDR-Blog driver branch you can force the bias tee to be always
    > on by setting a flag in the EEPROM.
    > The rtl_eeprom command is “rtl_eeprom -b y”.
    > Run the opposite command “rtl_eeprom -b n” to disable the forced bias tee.

    This method is absolutely not working!!!

    Already there are two complaints about this trouble.
    https://github.com/rtlsdrblog/rtl-sdr-blog/issues/8 (Sep 24, 2020 )
    https://github.com/rtlsdrblog/rtl-sdr-blog/issues/9 (New)

    Why is it taking you so long to fix this annoying trouble??

    • admin

      The problem is just that you must ensure that the rtl-sdr-blog drivers are the currently active drivers on your system. If you didn’t remove the previous drivers properly, then the system may still be using the old drivers which don’t recognize the EEPROM flags. The instructions for fully removing the old drivers is on the Git readme.

      • Nicholas

        Thank you for your answer, admin.
        Well, I removed the existing drivers.
        Then I installed osmocom drivers:
        https://github.com/rtlsdrblog/rtl-sdr-blog

        Now I check the status of the dongle:

        ~$ rtl_eeprom
        Found 1 device(s):
        0: Generic RTL2832U OEM

        Using device 0: Generic RTL2832U OEM
        Found Rafael Micro R820T/2 tuner

        Current configuration:
        __________________________________________
        Vendor ID: 0x0bda
        Product ID: 0x2838
        Manufacturer: Realtek
        Product: RTL2838UHIDIR
        Serial number: 00001006
        Serial number enabled: yes
        Bias-T Always ON: no
        Direct Sampling Always ON: no
        __________________________________________

        Here Bias-T Always ON: no

        Well, now I’m making a write Bias-Tee Always ON = yes

        ~$ rtl_eeprom -b y
        Found 1 device(s):
        0: Generic RTL2832U OEM

        Using device 0: Generic RTL2832U OEM
        Found Rafael Micro R820T/2 tuner

        Current configuration:
        __________________________________________
        Vendor ID: 0x0bda
        Product ID: 0x2838
        Manufacturer: Realtek
        Product: RTL2838UHIDIR
        Serial number: 00001006
        Serial number enabled: yes
        Bias-T Always ON: no
        Direct Sampling Always ON: no
        __________________________________________

        New configuration:
        __________________________________________
        Vendor ID: 0x0bda
        Product ID: 0x2838
        Manufacturer: Realtek
        Product: RTL2838UHIDIR
        Serial number: 00001006
        Serial number enabled: yes
        Bias-T Always ON: yes
        Direct Sampling Always ON: no
        __________________________________________
        Write new configuration to device [y/n]? y

        Configuration successfully written.
        Please replug the device for changes to take effect.

        At this moment, a voltage of +4.5V appears on the SMA connector.
        So the dongle is serviceable.

        Next, I make a reconnection USB of the dongle.
        But after that, the voltage on the SMA turns to 0 !!!

        I check the status of the dongle again:

        ~$ rtl_eeprom
        Found 1 device(s):
        0: Generic RTL2832U OEM

        Using device 0: Generic RTL2832U OEM
        Found Rafael Micro R820T/2 tuner

        Current configuration:
        __________________________________________
        Vendor ID: 0x0bda
        Product ID: 0x2838
        Manufacturer: Realtek
        Product: RTL2838UHIDIR
        Serial number: 00001006
        Serial number enabled: yes
        Bias-T Always ON: yes
        Direct Sampling Always ON: no
        _______________________________________

        Here Bias-T Always ON = yes

        This means that the writing was completed successfully.

        But why is there no voltage on the SMA ???

          • chill pill

            You really expect the man to drop everything right away to deal with you above all else? I have no doubt your issue has been seen. Patience is a virtue.

          • admin

            Could I please have more information about your system setup? I’ve just retested the EEPROM driver hack on a few systems and it’s working as expected. Does the bias tee run if you activate it manually via rtl_biast?

            One thing to note is that with the EEPROM hack the bias tee won’t turn on until a program that accesses the rtl-sdr-blog drivers is loaded. So when you plug it in the bias tee won’t automatically activate until you run some software.

            • Nicholas

              Ok. So, I use Debian 10.7 / 64 bit.
              When I run the this command –

              ~$ rtl_biast -d 0 -b 1
              Found 1 device(s):
              0: Realtek, RTL2838UHIDIR, SN: 00001006

              Using device 0: Generic RTL2832U OEM
              Detached kernel driver
              Found Rafael Micro R820T/2 tuner
              Reattached kernel driver

              a voltage of +4.5 V appears on the SMA connector.

              But when after that I run Gqrx or OpenWebRX, this voltage turns to 0.

              A similar situation occurs when executing the command -

              ~$ rtl_eeprom -b y

              • device

                Add ,bias=1 to the device string in gqrx (which otherwise turns off the device bias-tee when it starts).
                The device string should then look a bit like
                rtl=0,bias=1

                • aikd

                  I am finding similar issue. After enabling bias-T with rtl_biast -d 0 -b 1, I can measure voltage on dongle’s SMA. However starting rtl_power (after enabling bias-T through rtl_biast command) the voltage disappears. Host is RPI4 and dongle is rtl-sdr-blog v3 bought recently.

  5. Confused user Confuser

    Is there a technical description of how direct sampling mode works? I don’t get why it should matter if you’re reading “I branch” or “Q branch”. Additionally in direct sampling mode can we sample more than 2.5 MHz of instantaneous bandwidth?

  6. Maurizio

    Hello.
    I have a problem with my V.3 with the latest software sdr # (17.38) after a few minutes it crashes. with an old version (13.10) it works perfectly. For what reason?
    Maurizio

  7. Timothy Martin

    I am using an RTL SDR V3 with a Ham it up plus upconverter. I found that the V3 received HF signals very well on its own using direct sampling Q branch. However now that I have added a Ham it up Upconverter that offsets by 125 mhz, it is receiving very poorly, and only receives the strongest of HF signals. I changed the SDR sharp settings to Quadrature for use with the upconverter. If I switch the ham it up to passthrough, and change back to Q sampling, it receives fine again. Is there some other setting that I need to change? RF gain is set to max.

    • admin

      Optimizing gain is the main one for an upconverter, no other settings need to be changed apart from the offset and making sure you’re in quadrature sampling mode. Could it be a faulty upconverter, or adapter? What antenna are you using with it? How are you powering the upconverter?

      • Timothy Martin

        I am powering the upconverter with a USB cable hooked up to my computer. The antenna is a 10 / 20 meter fan dipole that I use for ham radio communications and works fine. If I switch the upconverter to bypass mode, and set the SDR to direct sampling Q branch, it picks up 10 and 20 meter ham signals as well as my ham radio. But if I switch the upconverter on, set the software for the SDR v3 to quadrature mode, and offset to -125,000,000, I get nothing on 20 meters, and on 10 meters I can only faintly receive a very strong local 10 meter beacon.

        If I switch the RTL SDR to quadrature sampling, it tunes in FM radio stations on its own just fine. Also picks up weather radio no problem either and AM airport tower signals. But using it with the upconverter, its near deaf.

  8. Sudhir Phakatkar

    Hello,
    I am using 100 KHz-1.7GHz Full Band UV HF RTL-SDR USB Tuner Receiver R820T + 8232 Ham Radio with software SDRsharp on my windows 10 laptop. I have found this working only for funcube dongle pro and NOT for RTL-SDR (USB). I am interested to use this set up for Radio meteor recording.
    Please guide me regarding this.

    • G7SYT

      hope this helps I use srd# community package with plugins
      wide fm 120 khz bandwidth METHEOR DEMODULATOR
      qpsk
      7200
      output to a file this will get you a S file put this though the LRPT off lind decoder and then finerley SMOOTH meteor to get the rectfide jpg hope this helps you can email me

  9. Dave

    @Jam – “usb_open error -12”

    I had the same problem. Look at the .bat files. You’ll find they are trying to control device 0 (parameter -d 0). For whatever reason, my RTL-SDR installed as device 1, so try change -d 0 to -d 1 or higher. See if that works? It did for me. Nice strong signals now 🙂

  10. Dave

    I had the same problem. Look at the .bat files. You’ll find they are trying to control device 0 (parameter -d 0). For whatever reason, my RTL-SDR installed as device 1, so try change -d 0 to -d 1 or higher. See if that works? It did for me. Nice strong signals now 🙂

  11. John M. POLARD

    Hello, can you be more specific how to use rtl-sdr v3 with HDSDR ? I use the latest version of it, when clicking on sdr device, I see my v3 but the direct sampling is in grey and I cannot activate it. Thank you for your reply
    John

    • Dave F

      it may have been “gray’ because it was in use ….. if You have the radio on Your unable to change some settings like under the COG (the pirates wheel thingy) but if Your turned off the radio and went back in Yours would allow You to chang modes sorry it took 2yrs to reply ;p

    • Dave

      I had the same problem. Look at the .bat files. You’ll find they are trying to control device 0 (parameter -d 0). For whatever reason, my RTL-SDR installed as device 1, so try change -d 0 to -d 1 or higher. See if that works? It did for me. Nice strong signals now 🙂

    • Ripley

      “usb_open error -12”

      I ran into this when I attempted to enable the bias tee via epromm command. Thought it bricked my device. I had to reinstall the driver via ZADIG in order to use the V3 again.

  12. john

    Am a novice at this. Have read the user guide. Instructions are vague and misleading. Computer does not recognize my RTL-SDR dongle. Keep getting message “no device selected” when turning dongle on.

  13. Bob

    BiasT, Gqrx on Linux

    I can turn on bias_T with ./rtl_bias -b 1 and measure 5V at the antenna terminal.
    I start up Gqrx and it turns Bias T off, no 5V at the antenna terminal.
    I run ./rtl_bias -b 1 again but now the device has been claimed by Gqrx ( this is normal)
    I changed the Gqrx device string to rtl=0,biast=1 Gqrx runs but no 5V at the antenna terminal.
    Also I notice CubicSDR doesn’t see the rtl-sdr V3 at all.
    I’d rather have it working with Gqrx. Not too keen on CubicSDR although it works well with SDRPlay RSP2.

      • Bob

        Thanks yarda. I actually worked it out by myself by experimenting. The ,bias=1 has to be added to the existing device string created when Gqrx found the rtl-sdr and not created in OTHER device string, my mistake.

        It woks now. but CubicSDR doesn’t see the device at all, but that’s another story.

  14. Al

    Using RTL-SDR V3 with Nooelec Sawbird + Goes. Works fine with my Windows 10 PC. Biast turns on and off as it should. When trying to run on my Windows 10 laptop I can not run the biast program. I get the following error:
    rtl-biast.exe – System Error
    The code execution cannot proceed because MSVCR100.dll was not found.
    Reinstalling the program may fix this problem.
    Tried running manually from CMD line and got same error. The MSVCR dll files are in system32.
    Any ideas for a fix??

  15. Yves

    The FM filter used for Q branch should be usefull also for VHF / UHF reception, pherhaps could you connect it for all configurations in future version. There are 10 $ RTL-SDR if we want to hear FM radio.
    For 500 KHz / 30 Mhz reception i use this loop antenna with 100 Ohms potentiometer at the entry of the RTL Dongle. Works nearly as good as sophisticated receiver, but more noise on audio that you can reduce with IF filter of SDRSharp.
    http://www.techlib.com/electronics/antennas.html

  16. Murray Craig

    you have marked the device with fcc and ce can you provide the letter of conformity as I have been asked for it by customers and if not would you be willing to work with us to get it?

  17. Simon

    Is there a way to enable Bias Tee on the V3 with a hardware mod? I have some gear that runs 24/7 and if there is a power dip, the Bias Tee disables, and it is a hassle to enable again.

  18. Yarda

    It seems the bias tee is supported by the upstream librtlsdr and osmosdr, could you update the instructions to cover it? For librtlsdr there is usually the -T option, e.g.:
    # rtl_fm … -T
    to activate the bias tee

    For the osmosdr the option “bias” can be used in the device string, e.g.:
    rtl=0,bias=1

  19. Al McIntosh

    Question – current version (download 20190329) does not have the option to select hf mode. It is greyed out. Did setup the current install software that came in the download. What step did I miss?

  20. Dave Frandin

    Is there a way to tell if I have a “version 3” unit? I tried adding the “rtl=0,direct_samp=2” to gqrx and it crashes gqrx… Same with “rtl=0,direct_samp=3″…

  21. Robby

    I cant use bais tee on Mac with gqrx… I enable it via ./rtl_biast -b 1 and then when I start Ggrx it turn off bias tee… Anybody had any luck

    • Phil

      In the gqrx device string window, you need to specify something like bias=1,rtl=0 (may need to change around in some cases). Try that.

    • willie

      it ain’t gonna work – used to in earlier versions of Gqrx and then i made the mistake of upgrading OSX and the app – now it won’t work no matter what…

      • Joe User

        willie, do you mean the app fails completely or just HF isn’t working? I’m running Gqrx 2.11.5 right now with OSX 10.14.6, although using an old non-TCXO Nooelec R820T while I wait for a RTL-SDR v3 to arrive. That dongle also works using CocoaRTLServer and SdrDx. Hope its not a fluke and the new one does still, too.

        • willie

          tks for replying! i am using a V3 RTL-SDR (i have a couple), along with Gqrx 2.11.5 under OS X 10.14.6 … the ‘direct_samp=2’ option simply doesn’t work… crashes… Gqrx defaults to ‘other’ – no reception, etc…

          what is frustrating is that it *did* work under older OS X and a previous version of Gqrx)… i have bookmarks that previously worked well… my feeling is that something changed in the underlying drivers/USB code or app?

          i also tried using CocoaRTLServer Version 2.0 (2), but that doesn’t work for me (could be that i’m not configuring/setting up correctly?)

          i would really like to see a step-by-step on how to set up using the current Gqrx and CocoaRTLServer under OS X Mojave – that would make the RTL dongle a real winner!

          (it does work fine for broadcast FM, VHF marine, NOAA WX…)

          regards,

          bill, kg4zqz

  22. Rehn

    Hi
    I bought a SDR dongle V3 from Electrokit in Sweden
    I have a problem i direct sampling mode.
    If I connect the dongle direct to my USB port I get nothing but the noise from the unit itself.
    With or without antenna connected.
    If I connect the dongle using extension cord I get some signal, but almost only very strong noise.
    It seems like its only the USB cord that function as antenna in direct sampling mode and the
    normal antenna connector is not used.

    Am I missing something, or is my unit broken ?

    regards
    John rehn

        • Robert Young

          You had this ” I have a problem i direct sampling mode. ” so if your using Q sampling then it is broken Quadrature is for 30MHz and up Direct Sampling (Q Branch) is for 30MHZ down to 500Hz.

    • Tom

      Sounds like you have noise pickup from the computer. And putting on the extension cable, it lowers the noise coming from it because of its distance. This might be an issue with antenna placement as HF is very susceptible to noise pickup. I would suggest trying coax running outside to the antenna sma connector. And note that an outdoor antenna could be picking up a lot of noise from all kinds of sources like power grid, motors, welders, tv’s and any other electrical noise source. Computers are very noisy as they generate square waves in 5 volt peak to peak signals that they operate on. But the vhf and higher frequencies tend not to pick this up very well as the harmonics are much lower in frequency.

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