April 3, 2015

New Web Based RTL-SDR Remote Control Software: YouSDR

Recently Kristian, a reader of our blog wrote in to let us know about a new software project he found that allows you to use your RTL-SDR remotely through a web interface. The web interface runs on Linux and uses mysql and the Apache server to work. Currently it can be used to access options for rtl_fm, rtl_tcp, dump1090 and can also be used to create an icecast audio stream.

The software can be downloaded from its Git at https://github.com/sixuniform/yousdr. The instructions on the GitHub page show how to set it up on a Raspberry Pi running Raspbian, but the instructions should also be valid for other Linux distributions. As the software is new the authors are welcoming any improvements and feedback.

Some similar web based RTL-SDR remote control software that you may be interested in includes WebRadio and rtl_fm_python.

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April 1, 2015

Spyverter Sneak Preview

The Spyverter is being developed by the creators of the Airspy software defined radio to be a high performance upconverter. It is designed for use with the Airspy, but may also be compatible with other SDR devices too.

Compared to most other upconverters which use a diode ring mixer architecture, the Spyverter uses a different, as of yet undisclosed architecture. The main claimed advantages over other upconverters will be it’s low loss and high IIP3 performance, which means that the Spyverter will not saturate in the presence of strong signals as easily as other upconverters.

Recently a photo of a Spyverter alpha board was released, indicating that the Spyverter is getting close to release.

Also, a few months ago W9RAN posted a YouTube video about a prototype HF upconverter for the Airspy and we believe he was using an early version of the Spyverter.

Airspy HF Converter Sneak Peek by W9RAN

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April 1, 2015

Direct Sampling 14 MHz Low Pass Filter and Galvanic Isolator for the RTL-SDR now for sale in Japan

Previously we posted about Japanese RTL-SDR experimenter Nobu and his work in prototyping a new 14 MHz low pass filter and galvanic isolator for use with the RTL-SDR. The low pass filter improves reception when using the RTL-SDR in direct sampling mode by reducing out of band interference and the galvanic isolator (isolation transformer) reduces computer and other noise when using the RTL-SDR with an upconverter.

The products can be bought from the Japanese Amazon store [Galvanic Isolator] [Low Pass Filter], however to purchase from outside of Japan you will need to use a third party shopping service available at http://agent.jzool.com/.

If you are interested in Nobu’s products, he also has direct sampling modified RTL-SDR dongles and dongles with 10 ppm crystals available, as well as his own upconverter for sale in Japan.

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March 31, 2015

Decoding and Plotting VOR Signals with an RTL-SDR: Part 4

Previously we posted about Will’s (aka hpux735) project [1] [2] where he has been using an RTL-SDR dongle to help understand and decode aircraft navigation VOR signals. VOR is an acronym for VHF Omni Directional Radio Range and is an older method of navigation used by aircraft which is used to provide a heading towards a VOR transmitter.

In his latest video, Will has been able to finish his code which allows him to actually plot some VOR data that he obtained from a flight on a map. In the video the VOR data is used to draw a heading line between three recorded VOR transmitters and the aircraft. The video clearly shows the accuracy of the VOR signals (about 1 degree) and shows what happens to the heading accuracy when reception is bad.

VORs and SDRs Part 4: Fusion!

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March 31, 2015

Some E4000 RTL-SDR Noise Figure Measurements

Over on Avian’s blog author Tomaz has posted about some noise figure measurements he has done with an E4000 RTL-SDR dongle. To do the measurements he used a vector signal generator and used the “Y-factor” and “twice-power” measurement methods with the output measured in GNU Radio.

In his results Tomaz saw some odd peculiarities as the twice-power and Y-factor measurements disagreed, coming out with noise figure values of 17.0 dB and 13.6 dB’s respectively. He isn’t sure what could be causing this disagreement but speculates that there must be some sort of physical process within the dongle causing these differences. He was also concerned about the larger than expected noise figure values, since the E4000 datasheet specifies a noise figure of 4 dB, though he points out that these datasheet values may be best case values only.

Measuring the noise figure of an E4000 RTL-SDR. — Measuring the noise figure of an E4000 RTL-SDR with a vector signal generator.

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March 29, 2015

RTL-SDR Front End Filter Demonstration

Over on YouTube user kugellagers has uploaded a video demonstrating the effect of some front end filters he constructed in order to reduce the effects of intermodulation from strong local AM and FM broadcast radio stations.

To attenuate strong broadcast FM signals, he used a very cheap FM trap from MCM Electronics. An FM trap (aka FM bandstop filter) is designed to attenuate signals in the FM band only. However, as a single FM trap was not strong enough for him, he took two FM traps out of their original casing and connected them together in a larger box for increased attenuation.

To attenuate strong broadcast AM signals he designed and created a home made 7th order LC elliptic high pass filter. With the filter in place he is able to receive a station at 2.5 MHz, but without it he shows that is unable to receive it clearly due to broadcast AM intermodulation.

RTL SDR Front End Filter Demonstration

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March 29, 2015

Analyzing the Radio Spectrum in Hong Kong with an RTL-SDR

Over on his blog, Gough Liu has made a post showing an analysis of the Hong Kong radio spectrum that he made while he was on a trip. In his analysis Gough used a locally bought DMB-T TV dongle (not RTL-SDR) for receiving digital TV and DAB+, a Dengen DE1103 for receiving AM and FM Broadcast and an RTL-SDR dongle for all other signals.

In his post Gough first talks about how he received DTM-B digital TV broadcast (similar to DVB-T and ATSC), and he does a full analysis of this service in another post. Next Gough talks about the Hong Kong digital radio DAB+ service and his finding where he saw that there was significant multipath selective fading in the DAB+ signal. He also found out that the HK DAB+ service broadcasts still images along with the audio.

Next Gough received the broadcast FM band and found that it was extremely crowded, providing poor distorted audio quality. He also attempted shortwave listening, but massive amounts of local interference prevented him from doing so.

Finally Gough took advantage of his harbour view hotel room to use his RTL-SDR to receive marine AIS transmissions. He used AISMon and OpenCPN to plot the boat positions on a map.

DAB+ Multipath Selective Fading in Hong Kong

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March 26, 2015

New Airspy Review from Radio User Magazine

Update: Note that we also now have our own comprehensive review available here which compares the Airspy, SDRplay RSP and HackRF.

A new review of the Airspy (store) software defined radio has been published by Mike Richards in the March 2015 edition of the Radio User magazine. Although the magazine is for sale, the publishers have allowed the Airspy team to release the review for free. The review goes over the Airspy architecture, features, use of the software and presents a favourable tone towards the Airspy.

The Airspy is an software defined radio that costs $199 USD and comes with a 24 – 1800 MHz tuning range, 10 MHz of bandwidth and 12-bit ADC.

Previously Mike Richards also reviewed the SDRPlay, a competitor to the Airspy in Radio User and that review is also available for download.