Intro to RTL-SDR & SDR#

Posted by admin on Mar 16, 2015


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Overview:

RTL-SDR uses a realtek digital television tuner and an antenna to receive radio signals, turning your PC or other device into a software defined radio.

This is not a new concept and SDR apps have been available even for smartphones for some time, but it's a great place to start if you are interested in RF. There are some great in-depth articles and other resources available over at RTL-SDR.com, or if you are looking for hardware to get started you can find some inexpensive starter kits at NooElec.

As an introduction to RTL-SDR this guide will show you how to set up SDR Sharp (SDR#) on Windows with a usb RTL-SDR dongle and use it to pick up FM radio stations.


You will need...

Hardware:

RTL-SDR reciever dongle - For this tutoial I'm using a NooElec NESDR Nano SDR & DVB-T USB Stick that uses the chip sets: RTL2832 + R820T with an aproximate frequency range of 25MHz - 1750MHz. You should be able to find these or a similar starter reciever for around $20/£15.

Antenna (RTL-SDR dongles usually come with a small antenna suitable for getting started, but you will probably want to replace this as you progress with sdr#)

Software:

SDR# (SDR Sharp)


1. Installing SDR#

Download SDR# from the downloads page at http://www.sdrsharp.com/ then extract it to a folder. Open this new folder and run the 'install.bat' file. When this has completed it will create a new folder called 'sdrsharp' containing the SDR# program files and the file zadig.exe.

2. RTL-SDR Dongle Set Up

Plug in your RTL-SDR dongle - it's best to choose a spare USB port that is not in the way and will be convenient for your antenna as once you have installed the WinUSB drivers you may have to use the same USB port for it to work next time. Now run the 'zadig.exe' file from the 'sdrsharp' folder as administrator. When Zadig opens you should get a screen similar to the one below but with blank boxes.

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If you try the drop-down device box you will probably find that there are no devices listed. To get our RTL-SDR device to show up you must open 'options' from the menu and check the option 'List All Devices', now when you look in the device drop-down list you should find the various devices attached to your computer. Select the device 'Bulk-In, Interface(Interface 0), then in the driver box select WinUSB and click 'Install Driver'. If windows has already loaded a driver then the 'Install Driver' button will read 'Reinstall Driver', so click that instead. If you get a warning box about driver verification, select 'install the driver software anyway'.

3. SDR# 

Run SDR# by running the 'SDRSharp.exe' found in the 'sdrsharp' folder.
Once the program has loaded you should see the default screen set up for SDR# similar to the following image. In the column on the left side of the window there should be a scrollable list of settings, and at the top of this list is the 'Source' setting where there should be a drop-down list. The RTL-SDR dongle should now show up in this list as 'RTL-SDR/USB' so now select it.

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Above the sources box are buttons for the menu, starting/stopping receiving, configuration, volume, and frequency. Turn on your speakers, click the play button and if you have correctly set up your RTL-SDR dongle you should see some movement in the FFT and Waterfall view ports.


Open the configure menu by clicking on the cog icon. Near the bottom of the window as a slider for the RF Gain. By default this is set to 0 so turning it up to around half way should allow you to receive more.

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Back on the main SDR# screen you can start seeking signals by dragging the top half of the screen and looking for peaks.
If you have adjusted the gain and you're now getting too much noise in the waterfall view it can make it hard to see weaker signals. You can fix this by adjusting the 'range' slider located under the 'FFT Display' panel to bring the noise floor down.

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Underneath the Source panel is the Radio panel which contains 8 radio buttons:

NFM - Narrow FM
WFM - Wide FM
AM - Amplitude Modulation
DSB - Double Side Band
LSB - Lower Side Band
CW - Continuous Wave
USB - Upper Side Band
RAW - Unprocessed IQ Data

For a quick test you can select WFM and then at the top of the screen type in the frequency of an FM radio station of your choosing. You should now be able to hear your radio station.You can drag the FFT or the IF Spectrum left and right to tweak the tuning. 

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Tuning to a local FM radio station is a quick method to check that your RTL-SDR setup is working without any major problems.

I will extend this post in the future to add more detail and cover more of the features of SDR sharp.


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