AISRec: Windows and Android AIS Decoder

Back in 2015 we posted about the free trial version of AISRec a few times, but we never really saw a full completed version get released. So far this year the full version is still not released, but the programmer Jane Feverlay has created a website and uploaded the latest Windows version of their trial version software. 

AISRec is an RTL-SDR compatible AIS decoder that is made for Windows and Android. AIS is an acronym for Automatic Identification System and is a system used by ships to broadcast position and vessel information. By monitoring AIS transmissions with the RTL-SDR we can build a boat radar system. We have a tutorial on this here (using other software).

The last time we tried AISRec we found that it had very good ability at decoding AIS messages, especially very weak ones and was by far the easiest AIS decoder to set up and use on Windows. The features include:

1. Work with all rtlsdr dongles. Allow future support for other SDR devices.
2. Stable reception of AIS signals at as low as SNR 7 dB.
3. Tolerance to frequency drifts > 30 ppm.
4. Dual-channel reception at 161.975 MHz and 162.025 MHz.
5. Channel selectivity > 56 dB.
6. Low CPU usage. No problem for Atom CPU and above.
7. Output all types of AIS messages (including Class A and Class B) in NMEA formats to UDP ports.
8. Convertion of AIVDM to AIVDO messages for your own ship.
9. Display of the received NMEA messages and the statistics.

The author of AISRec writes in an email to us an explains that the trial version has a time limit and an RX message count limit for each run, whereas the registered lite version will not. The pro version will have some additional features. Currently the author has no method for taking in paid registrations, but plans to have this ready in the future. We will post again once registration is available.

AISRec Running with OpenCPN
AISRec Running with OpenCPN

 

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Nooelec + AmateurRadio.com RTL-SDR Competition now Running

Hot on the tails of our own competition which has now closed, Nooelec and AmateurRadio.com have teamed up to create a giveaway for a HackRF One and 40 RTL-SDR dongles (some even bundled with upconverters)! They are giving away:

  • 1x HackRF One HF SDR Bundle (Includes upconverter and adapters)
  • 3x NESDR XTR+ HF bundles (a.k.a E4000 RTL-SDR + Upconverter)
  • 2x NESDR Mini 2+ HF bundles (a.k.a R820T2 RTL-SDR w/ TCXO + Upconverter)
  • 10x NESDR XTR+ sets (a.k.a E4000 RTL-SDR Dongles)
  • 10x NESDR Nano 2+ sets (a.k.a R820T2 w/ TCXO RTL-SDR in small “nano” package)
  • 15x NESDR Nano 2 sets (a.k.a R820T2 RTL-SDR in small “nano” package)

To enter all you need to do is comment on their blog post (not ours!). Their competition runs from 24 January 2016 20:00 UTC to 31 January 2016 20:00 UTC.

nooelec_comp

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Competition Winners Announced!

Firstly, thanks to all who entered our competition. We saw a huge response and learned a great deal about what the RTL-SDR community is up to these days. I encourage everyone to take a look through the comments on the competition post if you’re looking for project inspiration.

We ran competitions on Twitter, Facebook, the competition post itself and on our mailing list. We randomly chose 5 winners from each competition and will be sending them each one of our RTL-SDR Blog dongles. The 20 winners have now been selected. If you missed out, don’t worry – we hope to do more competitions like this again this year!

Facebook Winners!

Winners, please check your Facebook private messages. If you don’t see it, the message may be hidden in the spam inbox.

Zim Zimmerman – Currently working hard to overcome the NOISE related to living in an apartment complex in a Seattle suburb! TWO band pass filters; shielding via Al foil wrap and a directional antenna have helped. As hams say; “Good luck in the contest OM!” 73 K4IES

Sammy Truong – Exploring quickpass highway toll system.

Jimmy Vance – Just getting started with SDR dongles. For now will use them as general purpose receivers and spectrum analyzers

Amy Cstar – I’m a newbie and I’m hoping to use this to listen to the ISS 

Cezar Lesanu – Already running a radio meteor detection setup on RMOB and frequency stability and shielding are issues:http://www.rmob.org/livedata/main.php#Cezar Lesanu_ROAN@USV

Twitter Winners!

Winners, we’ve publicly tweeted you asking you to please email us directly. Please also tweet back at us confirming that you’ve received our notification.

Xizt ‏@RECEPTORR – Will use RTL-SDR dongle for learning wide band signals and monitoring Ham radio bands.

Rooster Mcdoogle ‏@RoosterMcdoogle – My first SDR project is going to be identifying/decoding local signals, and then satellites.

Sparkie Nelson ‏@SparkieNelson – Need a cheap spectrum analyzer for balloon beacon transmitter development.

DPini ‏@DPini – Right now, I’m trying to build a QFH antenna. My intention is to recieve NOAA and CubeSats

D M Miller ‏@bentmg – Hoping to set up a dedicated sdr to decode some DMR and NXDN signals in my area for streaming if I win the giveaway!

Blog Comment Winners!

We’ve emailed all blog comment winners using the email address that was provided. Please check your spam folder if you don’t see it, or contact us directly.

Jeff – Portable rf spectrum analysis

Stephen McBain – Starting out at the basics and using a dongle to decode different signals and just learning radio.

Matt – I’m working on building a WebSDR in Bucharest with full coverage from ~15mhz to ~1700mhz (R820T2 upper limit)

John Wilkerson – I use dual dongles for monitoring p25 trunked systems, as well as aircraft tracking.

Bryan – I’m pairing the RTL-SDR with my TS-940SAT and DXLab Commander + SDR# FTW.

Mailing List Winners! (Emails obscured for privacy)

We’ve obscured the winning emails for privacy, but we’ve emailed these winners now. Please check your spam inbox too!

g___e__e.r_i___i@____.com

j____p__a@____.com

v___o_t@________.ca

m_r___n@________.net

d_b___l_+_t_s_r@_____.com

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Reverse Engineering Cheap Chinese Radio Firmware

This post isn’t related to SDR, however it may interest many readers as it has the potential to become the “RTL-SDR” of handheld hardware radios. Recently at Shmoocon 2016 (a yearly hacking and security themed conference), hardware hacker Travis Goodspeed showed how he was able to reverse engineer the firmware of a cheap Chinese made Tytera MD380 DMR digital handheld radio transceiver.

The reverse engineering feat essentially means that custom firmware can now be written to the radio. They’ve already managed to add a promiscuity mode that allows the radio to be able to receive from all talk groups on a known repeater and timeslot. Access to he firmware now also means that custom decoders for protocols such as P25, D-Star or System Fusion can potentially be added to the radio’s features in the future. In the end this could turn this cheap $140 radio into a more featured radio that would be worth much more.

See the full story over at Hackaday and the white paper here (start at page 76) and the video of the talk below.

Jailbreaking a Digital Two Way Radio Travis Goodspeed travisgoodspeed

Inside the Tytera MD380
Inside the Tytera MD380
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SDRDX Now supports the RTL-SDR on OSX

SdrDx is a free software defined radio application that was originally written to support SDRs built by RF Space. However these days it appears to support multiple other SDRs including the Funcube, Andrus, Peaberry/Softrock and AFEDRI SDRs.

In the latest update they have also added support for the RTL-SDR on OSX. An RTL-SDR dongle is able to connect to the SdrDx program via a special OSX based RTL-SDR server called CocoaRTLServer. At the moment it appears that rtl_tcp is not supported as it does not use the protocol required by SdrDx, so Windows and Linux computers cannot use this software.

Compared to other general purpose SDR receiving software SdrDx has some interesting features not seen in most SDR software that supports the RTL-SDR. The full feature list and list of currently supports SDRs can be found here.

The SdrDX main screen.
The SdrDX main screen.
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Airspy and Spyverter using a GPSDO

Recently Tim Havens (NW0W) wrote in to use to let us know about his work in connecting the Airspy and Spyverter to a very accurate GPS disciplined oscillator (GPSDO). Usually the drift on the Airspy and Spyverter is completely negligible, however Tim uses them together with his Yaesu FTDX-5000 for monitoring CW signals. He wanted to be able to click on a CW signal and have his FTDX-5000 tune to the signal perfectly every time, so even very small oscillator drift offsets could affect his tuning.

To get a high accuracy clock signal from a device such as a GPSDO can be used for both the Airspy and Spyverter. Tim was able to find a very nice GPSDO from Leo Bodnar that comes with two clock separate outputs that can be configured to output any frequency between 450 Hz and 800 MHz. 

The Airspy already contains an external clock input for 10 MHz, however the present version of the Spyverter contains no such external input. To get around this Tim carefully removed the oscillator on the Spyverter and then added a second SMA connector to connect to the GPSDO.

His final setup consists of the Leo Bodnar GPSDO outputting a 10 MHz and 120 MHz GPS disciplined clock signal that feeds the Airspy and Spyverter respectively. With this Tim found that he needed no initial offset and zero drift was noticed over two days of testing.

Finally Tim also writes that this Leo Bodnar GPSDO could just as easily be used to create a 28.8 MHz clock signal for an RTL-SDR, or any other SDR or upconverter that needs it. 

Modded Spyverter with external clock input.
Modded Spyverter with external clock input.
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Receiving AERO-H on L-Band with an RTL-SDR

Over on YouTube Adam Alicajic (9A4QV – creator of the LNA4ALL and upcoming MIX4ALL) has uploaded a video showing his reception of AERO-H signals from an Inmarsat satellite. A few days ago we posted about how the JAERO decoder had recently been updated to be able to decode these AERO-H signals. These signals contain various messages meant for airplanes, but also sometimes contain news messages.

In the video Adam uses a satellite dish antenna together with his MIX4ALL, an RTL-SDR dongle and the JAERO software. With decent reception he is able to easily decode the AERO-H messages.

Receiving AERO-H on L-band (Inmarsat AOR-W)

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Demonstrating Radio Frequency Interference with an Airspy

Over on YouTube user Ejo Schrama has uploaded a short video showing a demonstration of radio frequency interference (RFI) from various Arduino based devices he’s built. The interference comes from the local oscillators within the devices which are common to many electronic devices. He writes in the video description:

RFI simply means that there is a part in the radio spectrum that we wouldn’t like to see, it is usually unintentionally caused by devices around us (computers, televisions, radios, clocks, watches, etc etc) that carry local oscillators which are low power transmitters. Sometimes it is caused by illegal transmissions, so a deliberate action.

The oscillators of devices around us oftentimes feed digital circuits, sine wave become block wave, as a result higher order harmonics of the block wave pollute the spectrum. If your receiver is sensitive enough then you will pick up the RFI at some point.

In this video I’m two meter away from an antenna and I tuned the receiver to 48 MHz which is the 3rd harmonic of the 16 MHz oscillator used by all nearby Arduino experiments. Lets see what the spectrum does by turning on and off some arduino’s. The worst RFI generator was a 16 MHz atmel 328p multiplexing four 7-segment LEDs displaying the value of a IR temperature sensor. But also a nearby clock experiment clearly caused some RFI.

The receiver that I used was an airspy, and I’ve put the decimation factor high enough to get some resolution in the spectrum. The frequency offset between the different arduino’s is clearly visible. This is caused by the fact that cheap quartz oscillators are used, their accuracy is usually around 100 ppm, and this mostly determines a frequency bias.

Nowadays it is very difficult to clean up your local shortwave spectrum. For this reason reception conditions under 30 MHz and even 2 meter nowadays face the RFI problem. Only when we go to UHF frequencies like 430 MHz, better known as the the 70 cm amateur band, the RFI problem sort of disappears, apparently because higher harmonics have become insignificant.

I do not think that a lot of effort is put into keeping LW, HF but also VHF spectra clean, the worst violators are usually tracked down but only when many listeners start to complain.

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