Analyzing GSM with Airprobe/GR-GSM and Wireshark

The RTL-SDR software defined radio can be used to analyze cellular phone GSM signals, using Linux based tools GR-GSM (or Airprobe) and Wireshark.

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RTL-SDR for Budget Radio Astronomy

With the right additional hardware, the RTL-SDR software defined radio can be used as a super cheap radio telescope for radio astronomy experiments such as observing the Hydrogen Line and meteor detection.

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Receiving NOAA Weather Satellite Images

Everyday multiple NOAA weather satellites pass above you. Each NOAA weather satellite broadcasts an Automatic Picture Transmission (APT) signal, which contains a live weather image of your area. The RTL-SDR dongle combined with a good antenna, SDRSharp and a decoding program can be used to download and display these live images several times a day.

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Decoding Digital Voice (P25, DMR, NXDN, D-STAR) with DSD+

Learn how to decode digital voice communications like APCO P25, DMR MotoTRBO, NXDN and D-STAR with DSD+ and an RTL-SDR dongle.

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Decoding DRM Radio

Digital Radio Monodial (DRM) radio is a type of digital shortwave radio signal that is used by international shortwave radio broadcasters. It provides superior audio quality compared to AM signals by using digital audio encoding. With an upconverter, good antenna, and decoding software the RTL-SDR software defined radio can receive and decode DRM signals.

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List of SDRSharp Plugins

There are a number of SDRSharp plugins that extend its functionality. Here is a collection of all the plugins and download links that we know of.

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Receiving Weather Balloon (Radiosonde) Data with RTL-SDR

Use your RTL-SDR to decode data from weather balloons (aka Radiosondes) that are launched twice daily by meteorological agencies all around the world.

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POCSAG Pager Decoding

Decode POCSAG pager messages with an RTL-SDR. Even in the modern day pagers are still popular with doctors, some fire and ambulance agencies and various service companies, as they tend to be more reliable and have greater coverage.

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Roundup of Software Defined Radios

New software defined radio (SDR) products are popping up every few months these days so we thought we’d compile a big list of available SDRs.

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The BIG List of RTL-SDR Supported Software

There are now dozens of software defined radio packages that support the ultra cheap RTl-SDR. In this post we will attempt to list, categorize and provide a brief overview of each software program.

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SDR Soundcard Mod

Yesterday we got an email from a reader (Tom) about a soundcard capacitor mod that is useful for SDRs. Tom writes

First you buy one of these sound cards: Creative Soundblaster X-Fi Surround 5.1 Pro USB (various internet sources)

Then you make the following mods: http://www.rfsystem.it/shop/download/SB_Creative_XFi_Pro_USB.pdf

I did the capacitor mod and it makes a HUGE difference, and there is a bonus. Not only do you get an excellent, very low noise sound card, but the drivers include a “what u hear” mixer that works find on Windows 7 so you don’t need to buy a separate virtual audio cable.

The unmodified  Soundblaster X-Fi had somewhat fewer noise spikes showing up across the spectrum on SDR# than my internal soundcard. However when I did the capacitor mod, they decreased by a drastic amount. Before I realized the extent of the original internal noise spikes, I wasted time trying to “decode” them – worked about as well as my attempts to communicate with aliens via my dental work.

So now my SDR# display looks really clean and most everything that looks like a signal is a signal. I don’t have before and after pictures, but the ones in the pdf file look like mine.

BTW the capacitor values are probably not all that critical. I used a couple I had laying around – a 1000 uF 16v and a 120 uF 16v. Anyone with some soldering experience and a reasonably small tip can do the mod but it’s a little tricky to position the caps and have the case close properly. The unwary might get polarity confused – the tantalum caps on the board are marked on the positive end and the electrolytics you add are marked on the negative end.

The capacitor mod essentially involves soldering in two more capacitors onto the soundcard PCB. The improvement is more useful for soundcard based SDRs such as the SoftRock, however, in Toms case he found that the capacitor mod also improved his RTL-SDR reception by removing numerous unwanted noise spurs he was seeing.

Since the RTL-SDR is not a soundcard based SDR, in Toms case the external soundcard was probably causing strong interference that the RTL-SDR was picking up, and the capacitor mod treated the noise source.

The mod may also help by giving you a cleaner audio signal, which may help when decoding digital signals.

SDR Soundcard Mod

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