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Nearly all of the guides that I used for reference I found through the /r/RTLSDR subreddit, there are many helpful people and a lot of ideas about ways to improve the performance of the system, including pre-amp designs, metal cases and USB-cable filters.

I will endeavour to keep this page updated but please let me know of any updates/errors/additions you find.


The software and fragmented instructions can be found on the spench.net Wiki USRP Page.

  1. Install ExtIO_USRP+FCD+RTL2832+BorIP-BETA_Setup.zip (Direct Link) - Install both HDSDR and ExtIO in the same folder.
  2. When the Zadig installation begins (part of the automatic process), look in the devices drop-down box. Then plug in your rtl-sdr dongle and look again. For the first subdevice that appears (sometimes it will be one, most times two), install the WinUSB driver.
  3. After the installation completes, download the updated librtl2832++.dll (Direct Link) and replace the copy existing in the folder where you installed HDSDR.
  4. Launch HDSDR.
  5. Select ExtIO_USRP.dll for ExtIO source in the Options menu. This will allow connection to the USRP/FCD/RTL-SDR devices.
  6. Click the 'ExtIO' button to bring up the Device Options if it hasn't appeared already and add RTL tuner=e4k to the Device Hint, click 'Create'.

Assuming your tuner is plugged in, this should set up the relevant options. From here you can tune/mess with the 'Sample Rate' as well as 'Gain/Attenuation' of the front-end.

Click Start on the main HDSDR window and RF should start rolling down the waterfall! Have Fun!

Modem Programs

As a Radio Ham interested in Digital Modes, I often use HDSDR with a Digital Modem program, such as APRSISCE, fldigi or dl-fldigi for High Altitude Ballooning telemetry. To feed the audio output of HDSDR into a Modem Program there are 3 methods.

  1. Connect an Audio cable from Line-Out to Line-In - This is the simplest, and will work when nothing else does, but is not ideal, as noise can be added and signal lost in the Digital => Analog => Digital conversion.
  2. Stereo Mix (requires Windows 7 and decent drivers) - If you are using Windows 7, open your Sound control panel, go to the 'Recording' tab and right click on the background to make sure both options to Show Devices are checked. If there is a 'Stereo Mix' object visible then you can use this as an input for the Modem Program, enable it and it will pipe through whatever is audible on your Line-Out.
  3. Use Virtual Audio Cable - In order to use this legally, you will have to buy it, as the trial version mixes in a human voice every few seconds, corrupting most digital data. This effectively creates an object similar to the 'Stereo Mix' previously described and allows tweaking of the sample rate as well as many other options.

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