SDR Radio: Getting started with lo-buck Software Defined Radio

Software Defined Radio is popular among computer and radio enthusiasts. It’s still a radio but uses a computer interface as opposed to traditional knobs and dials. Entrance fees for this hobby vary from ~$20 to well over $2000. In this article, I’m going to focus on the lower end of that scale using a repurposed DVB-T dongle.

DVB-T stands for Digital Video Broadcasting – Terrestrial. It’s the European based standard for OTA (Over-The-Air) digital television broadcasts from local mountain-top transmitters. It is not satellite. Low cost DVB-T dongles are available that plug into a USB port and turn a computer into a television. They’re essentially broadband receivers. While they don’t work for receiving TV in the US, with the right software they can receive many kinds of transmissions in the VHF-UHF range such as broadcast FM stations, NOAA weather radio, Ham/Amateur radio, Aircraft and much more. Just like a radio scanner, but with a cool spectrum display.

 

SDR does more than a conventional radio scanner and looks a lot cooler.

 

Be sure to get the right one as there’s a few variants to choose from. Most use the RTL2832 demodulator and USB interface and that’s why they’re called RTL-SDR dongles. There’s several choices of tuner chipset, the more popular ones are:

R820T 24-1766 MHz One of the original chipsets
R820T2 25-1750 MHz Increased sensitivity and SNR over the R820T (Preferred)
E4000 55-2300 MHz Greater freq range but not ideal for ADS-B
FC0013 22-1100 MHz Fiticomm Tuner

You’ll also want to make sure the unit you purchase has ESD protection, otherwise they’re reported to be sensitive to failure by static during routine handling. Look for a reference to BAV99, it’s a diode. I have one based on the R820T2 tuner from RTL-SDR.com which also hosts a great deal of how-to and tech support information. nooelec.com is another good source.

Once you’ve gotten a hold of your dongle, plug it into an available USB 2.0 port. If possible, use a dual-core or better PC. While Linux is my OS of choice, configuration can be a bit of a hassle and the preferred software for working with these gizmos is SDR# (pronounced SDR Sharp) for Windows. It’s fast, simple, stable, easy to configure and has a variety of plug-ins available to extend capability.

SDR# is available at sdrsharp.com and a good installation guide is available at rtl-sdr.com under the Quick Start tab.

 

A few tips for installation:

– Don’t install any drivers that came with the dongle. SDR# has everything you need.

– It doesn’t seem to work in a virtualized Windows nor under Wine in Linux. Bummer!

– SDR# doesn’t add itself to the menu, but you can place the folder anywhere you want and create a shortcut.

– A dual-core CPU or more is preferred. For modestly powered PC’s, click the ‘configure’ icon and adjust the ‘Sample Rate’ to a lower value.

– If you’re not receiving much, click the ‘configure’ cog icon and turn up the RF gain. Experiment with the ‘RTL AGC’ and ‘Tuner AGC’ settings. AGC = Automatic Gain Control and different settings work best depending on what you’re trying to tune in.

 

Once everything is working, it should look like this example receiving a Broadcast FM station.

 

Each peak is a radio station.

Each peak is a radio station.

 

So there you have it, a wide-band general coverage VHF-UHF receiver capable of receiving analog transmissions for a total investment of about $20! And that’s just the beginning. With additional plugins and software, one can receive many types of digital transmissions such as ADS-B aircraft transponders and more.
-Kenn Ranous

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