December 31, 2014

Techniques for using the RTL Dongle for Detecting Meteors

Back in 2013 we posted about a Dr. David Morgan who had written a tutorial paper discussing how he used the Funcube Dongle Pro+ for radio astronomy. Recently Dr Morgan has also written another paper showing how to use the RTL-SDR together with the Spectrum Lab software to detect meteors.

A software defined radio can be used to detect and count meteors entering the earth’s atmosphere by detecting strong radio waves reflected by ionized trails left by the meteor. If you are unfamiliar with how to detect meteors using radio waves, you should consult Dr Morgans older papers called Detection of Meteors by RADAR, Meteor Radar SDR Receiver (Funcube Dongle), and Antennas for Meteor Scatter. The tutorial shows how to set up SDR# and Spectrum Lab to work together to detect meteors using the Graves Radar in France at 143.050 MHz.

Meteor Scatter Detection in Spectrum Lab

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December 30, 2014

Receiving VLF with an Upconverter and Direct Sampling RTL-SDR

Recently amateur radio hobbyist DE8MSH wrote in to let us know about how he was able to receive VLF (Very Low Frequency) signals using a very rare Refcom FC-VLF upconverter and his direct sampling modified RTL-SDR.

His antenna is the PA0RDT mini whip which requires 12v of power that is delivered directly by the Refcom FC-VLF. He writes that the Refcom upconverter is used to upconvert the 9 to 50 kHz range into the 14.009 to 14.050 MHz range which is receivable by a direct sampling modified RTL-SDR. Using this set up he was able to receive several VLF stations as shown on the waterfall image below.

15 - 70 kHz VLF Received with an Upconverter and Direct Sampling RTL-SDR — 15 – 70 kHz VLF Received with an Upconverter and Direct Sampling RTL-SDR

DE8MSH also writes

Note that I’m not living in a quiet area. As you can see there is a lot of men made noise like from tv sets, lights bulbs etc. pp. Some signals are not very strong becaus I switched the Refcom to 9-50kHz filter. So some stations above 50kHz could be stronger.

Below are some close up shots of VLF signals being received.

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December 30, 2014

Chaos Communications Congress Talks – Iridium Pager Hacking

A few days ago the Chaos Communications Congress (a technology and hacking focused conference) commenced. Among the talks there was one about reverse engineering the Iridium satellite paging system using software defined radio. Iridium satellites provide global communications via special satellite phones, pagers and other transceivers.

In the talk the speaker shows how they used a USRP radio together with a cheap active iridium antenna, a bandpass filter and an LNA to receive the Iridium satellite signals. They also mention that an E4000 RTL-SDR together with an LNA and appropriate home made antenna for frequencies in the ~1.6 GHz region can also be sufficient. Once they were able to receive signals they were then able to reverse engineer the signal and create several pieces of software to decode the pager messages. The code is available on their GitHub at https://github.com/muccc/iridium-toolkit.

Sec, schneider: Iridium Pager Hacking

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December 29, 2014

Freqwatch – RTL-SDR Frequency Scanner and Recorder

Freqwatch is a new Linux based software program that has recently been released by programmer Joshua Davis. Freqwatch makes use of rtl_power to scan a wide swath of RF spectrum and then automatically records and stores in a database sound files of active signals by using rtl_fm.

The software is capable of making use of multiple RTL-SDR dongles in order to efficiently monitor larger bandwidths. After running the software for a while and generating a large database, you can then use a database analyzer like Splunk to find trends in the data or find out when something changes.

The software can be downloaded from its GitHub at https://github.com/covertcodes/freqwatch. Previously we featured some other software called ScanEyes which has a similar logging feature but focused on trunking radio channels and we also featured RTL Airband which monitors multiple airband frequencies simultaneously for logging and streaming.

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December 23, 2014

Chrome RTL-SDR Radio Receiver Updated

Chrome Radio Receiver has been updated and now supports NFM, AM, LSB and USB reception modes. The software can be downloaded for free from the Chrome store. Chrome Radio Receiver is a simple Javascript based RTL-SDR radio receiver without any spectrum or waterfall graphs. It is perfect for quickly listening to saved stations. The software also has the ability to record audio, save stations and automatically scan looking for active frequencies.

In order to receive AM/LSB/USB radio on HF frequencies you will need to use an upconverter and input the frequency offset in the settings menu.

[First seen at http://blog.livedoor.jp/bh5ea20tb/archives/4893438.html]

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December 23, 2014

Listening to SSTV from the ISS with an RTL-SDR

On December 18 and 20 the International Space Station transmitted several SSTV images to celebrate what would have been the 80th birthday of Yuri Gagarin who was the first human to orbit the Earth. SSTV stands for Slow Scan Television and is a method for sending small low resolution images over radio.

Over on YouTube several RTL-SDR users captured these images. UltraTechie shows a video where he captures the SSTV image using a portable set up consisting of a Windows 8 tablet running SDR#. He used a handheld 3 element 2m Yagi antenna to tune into the 145.8 MHz signal. UltraTechie writes that he also used an LNA, but that it was probably not required as the signal was quite strong.

ISS SSTV reception on a portable setup using RTL-SDR

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Another YouTube user Tom Mladenov shows another video where the SSTV image is received. Tom used a QFH antenna.

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December 23, 2014

SDR Comparison: Airspy vs Funcube vs E4000 RTL-SDR vs BladeRF

Over on YouTube user sm5bsz (aka Leif, programmer of Linrad) has uploaded a video showing an in depth technical comparison between the Airspy, Funecube, E4000 RTL-SDR and BladeRF software defined radios. His test focuses on the dynamic range when each SDR is used as a narrowband receiver at 144 MHz with appropriate filtering applied. The video is quite long and technical, but most of the results are summarized at 4:41.

SDRcompareTunersNarrow

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December 18, 2014

Testing Keenerds RTL-SDR Drivers

Keenerd (aka Kyle Keen) recently ran a fundraiser to support him to work on improving the RTL-SDR driver and related software. A few months ago he released an update to the driver which made some improvements including some tweaks by another programmer teejeez that optimized the R820T’s filters which may help with out of band aliasing. The list of issues he is working on and has completed can be found at http://igg.kmkeen.com/.

To use keenerds drivers on Windows with SDR# you can go to http://igg.kmkeen.com/builds/, and download the latest build zip file. Then simply copy all the non .exe files into the SDR# folder and rename librtlsdr.dll to rtlsdr.dll. We recently tested the new drivers and show screenshots of the difference below. Nearby to the marine weather report frequency used in the screenshots is a very strong pager signal which causes significant interference. With the gain turned up on the original drivers the entire band is wiped out when the pager signal is transmitting. With keenerds drivers most of the band is usable and the weather signals can be heard. There do seem to be some issue with what looks like WFM interference appearing now however. Testing at other frequencies with nearby strong signals also seem to show that aliasing is significantly reduced. We also noticed a lower noise floor at some frequencies resulting in about a 2-3 dB better signal. However, we also noticed that the noise floor was raised slightly at some other frequencies. We suggest you give keenerds drivers a try and comment with any improvements or issues you see.

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