Category: RTL-SDR

CubicSDR v0.1.4 Beta Released

CubicSDR is a new and upcoming multi platform open source SDR software package that is compatible with the RTL-SDR. It is similar to programs like SDR#, HDSDR and SDR-Radio. Recently the programmers have released version 0.0.4-beta which adds several new features which we have listed below:

  • Audio Spectrum visuals, drag the A/V visuals area to toggle between audio Scope and Spectrum
  • Waterfall speed can now be controlled between 1 and 1024 lines per second
  • Waterfall now continues to render while minimized or in background
  • Waterfall/Spectrum can now be zoomed to 30khz window with improved resolution
  • Spectrum averaging speed can now be controlled between 1% and 99%
  • I/Q mode for piping decimated I/Q to other applications at audio sample rate
  • Spectrum peak and floor decibels now displayed (can toggle off/on with ‘B’)
  • Can now mute demodulator with ‘M’ button or pressing ‘M” while hovering
  • Save and recall device Offset, I/Q swap, Direct sampling, Waterfall/Spectrum speed, Window state
  • Performance and UI responsiveness improvements
  • Can now use direct input for demod bandwidth
  • Direct input < 3000 now assumes Mhz
  • Additional device input sample rates
  • Improved waterfall keyboard controls via arrow keys
  • Can now specify alternate configuration name via -c (name) or -config (name) at command line
  • Automatically reduce unused buffer memory over time
  • Several crash fixes

CubicSDR is compatible with Windows, Linux and MacOS. It can be downloaded from www.cubicsdr.com.

CubicSDR v0.1.4 Demonstration

Showing how the R820T stops receiving at 1.4 GHz+ with increasing temperature

Over on YouTube RTL-SDR experimenter Adam 9A4QV has uploaded a video showing how the R820T dongle can fail to receive properly at frequencies above about 1.4 GHz as the temperature in the dongle rises. This is a known problem that may cause issues when trying to receive satellite signals like Inmarsat at 1.541450 GHz. In our own tests, the R820T2 chip appears to be much less prone to this behaviour when compared with the R820T, but still fails if the ambient temperature gets too hot, for example if left in direct sunlight. We’ve had several R820T2 RTL-SDR’s running at 1.5 GHz+ for over 48 hours when left in the shade, but not one R820T ran for more than a few minutes at those frequencies. Of course the E4000 tuner is the best RTL-SDR tuner for these GHz level frequencies, but that tuner is now rare and expensive.

Over on Reddit, some people have been discussing this issue, and have proposed that the likely cause is related to the PLL failing to lock properly at higher temperatures. A fix may be to apply a blob of solder to the vias underneath the R820T chip, and then attach a heatsink. The problem also does not occur on the Airspy, a higher performance SDR that also uses the R820T2 chip in its design. This may be due to better drivers for the Airspy, or better heat dissipation in the Airspy’s hardware design.

R820T stop receiving @ higher frequencies

Reverse Engineering Bus Telemetry Data with an RTL-SDR

Bastian recently wrote into us at RTL-SDR.com to let us know that he’s been working on reverse engineering the bus telemetry system used in his hometown of Paderborn, Germany. Bus telemetry is often used to update live signs at bus stops that indicate based on GPS data how long a bus user needs to wait for the next bus.

Bus sign: Wireless bus telemetry updates this sign.
Bus sign: Wireless bus telemetry updates this sign.

A similar reverse engineering of bus telemetry was performed before by Oona Raissan in Helsinki, Finland. Oona found that in Helsinki bus telemetry was transmitted as a DARC subcarrier embedded in regular broadcast FM radio. In many countries bus telemetry runs through GSM or TETRA communications as well, which are encrypted and would be very difficult to decode.

However in Paderborn, Germany Bastian discovered that the bus telemetry system used a different protocol which he discovered by noticing that some very strong signals appeared on his spectrum at 150.9 MHz whenever a bus drove by his flat.

After making a recording of this signal in GQRX, bastian analysed it in Audacity and discovered that the binary data bits were encoded by the presence or absence of a half sine wave. After discovering the encoding he was then able to determine the bit rate and build a decoder in GNU Radio. His post goes into further detail about concepts he used in his GNU Radio program such as frame detection, bit stuffing and error detection.

Finally, with all his decoder program written he was able to gather lots of data from each packet such as the bus ID, line, bus stop, distance from last bus stop, delay, position and even the orientation of the bus. Bastian has also uploaded a video showing everything in action, which we have embedded below.

Bus position heatmap from data obtained via the RTL-SDR
Bus position heatmap from data obtained via the RTL-SDR

A new AIS Decoder for the RTL-SDR on Android

A reader of our blog, EBC81, has written in to let us know about a new RTL-SDR based AIS decoder that he has written for the Android OS. AIS stands for Automatic Identification System and is used by ships to broadcast their GPS locations, to help avoid collisions and aid with rescues. An RTL-SDR with the right software can be used to receive and decode these signals, and plot ship positions on a map.

EBC81’s program is called rtl_ais_android and can be downloaded from this GitHub link. It decodes the AIS data into NMEA messages, which can then be sent via UDP to mapping programs in Android or a program like OpenCPN on your PC. To use the app you will need a USB OTG cable to connect your Android device to the RTL-SDR.

In the future EBC81 hopes to create a second app which will display the ship positions on a map.

RTL-SDR Tutorial: Decoding Inmarsat STD-C EGC Messages

Inmarsat is a communications service provider with several geostationary satellites in orbit. They provide services such as satellite phone communications, broadband internet, and short text and data messaging services. Geostationary means that the satellites are in a fixed position in the sky and do not move. From almost any point on earth at least one Inmarsat satellite should be receivable. 

Inmarsat transmits in the L-band at around 1.5 GHz. With an RTL-SDR dongle, a cheap $10 modified GPS antenna or 1-2 LNA's and a patch, dish or helix antenna you can listen to these Inmarsat signals, and in particular decode one channel known as STD-C NCS. This channel is mainly used by vessels at sea and contains Enhanced Group Call (EGC) messages which contain information such as search and rescue (SAR) and coast guard messages as well as news, weather and incident reports. More information about L band reception is available at UHF-Satcoms page. See the end of this post for a tutorial on modifying a GPS antenna for Inmarsat reception.

Some examples of the EGC messages you can receive on the STD-C NCS channel are shown below:

Military Operations: Live Firing Warning 
STRATOS CSAT 4-AUG-2015 03:21:25 436322
SECURITE
FM: RCC NEW ZEALAND 040300 UTC AUG 15

COASTAL NAVIGATION WARNING 151/15

AREA COLVILLE, PLENTY
CUVIER ISLAND (REPUNGA ISLAND), BAY OF PLENTY
1. LIVE FIRING 060300 UTC TO 060500 UTC AUG 15 IN DANGER AREA NZM204. 
ANNUAL NEW ZEALAND NOTICES TO MARINERS NUMBER 5 REFERS.
2. CANCEL THIS MESSAGE 060600 UTC AUG 15
NNNN
Armed Robbery / Pirate Warning 
NAVAREA XI WARNING
NAVAREA XI 0571/15
SINGAPORE STRAIT.
ARMED ROBBERY INFORMATION. 301845Z JUL.
01-04.5N 103-41.8E.
FIVE ROBBERS ARMED WITH LONG KNIVES IN A SMALL UNLIT HIGH SPEED BOAT APPROACHED A BULK CARRIER UNDERWAY.  ONE OF THE ROBBERS ATTEMPTED TO BOARD THE SHIP USING A HOOK ATTACHED TO A ROPE. ALERT CREW NOTICED THE ROBBER AND RAISED THE ALARM AND CREW RUSHED TO THE LOCATION. HEARING THE ALARM AND SEEING THE CREW ALERTNESS, THE ROBBERS ABORTED  THE ATTEMPTED ATTACK AND MOVED AWAY. INCIDENT REPORTED TO VTIS SINGAPORE. ON ARRIVAL AT SINGAPORE WATERS, THE COAST GUARD BOARDED THE SHIP FOR INVESTIGATION.

VESSELS REQUESTED TO BE CAUTION ADVISED.
Armed Robbery / Pirate Warning 
NAVAREA XI WARNING
NAVAREA XI 0553/15
SINGAPORE STRAIT.
ROBBERY INFORMATION. 261810Z JUL. 
01-03.6N 103-36.7E. 
DUTY ENGINEER ONBOARD AN UNDERWAY PRODUCT TANKER DISCOVERED THREE ROBBERS IN THE ENGINE ROOM NEAR THE INCINERATOR SPACE. THE ROBBER THEIR BOAT. A SEARCH WAS CARRIED OUT. NO ROBBERS FOUND ON BOARD AND NOTHING REPORTED STOLEN. VTIS SINGAPORE INFORMED. COAST GUARD BOARDED THE TANKER FOR INVESTIGATION UPON ARRIVAL AT SINGAPORE PILOT EASTERN BOARDING AREA.VESSELS REQUESTED TO BE CAUTION ADVISED.
CANCEL 0552/15.
Submarine Cable Repair Warning 
NAVAREA XI WARNING
NAVAREA XI 0569/15
NORTH PACIFIC. 
SUBMARINE CABLE REPAIRING WORKS BY 
C/V ILE DE SEIN. 05 TO 20 AUG. 
IN VICINITY OF LINE BETWEEN 
A. 21-37.3N 156-11.5W AND 25-03.6N 148-43.2E.
CANCEL THIS MSG 21 AUG.
Search and Rescue - Missing Vessel 
ON PASSAGE FROM LAE (06-44S 147- 00E) TO FINSCHHAFEN (06-36S 147-51E), MOROBE PROVINCE. VESSEL DEPARTED LAE AT 310500Z JUL 15 FOR FINSCHAFFEN WITH ETA OF 310800Z JUL 15 BUT FAILED TO ARRIVE. 
ALL VESSELS REQUESTED TO KEEP A SHARP LOOKOUT AND BE PREPARED TO RENDER ASSISTANCE. REPORTS TO THIS STATION OR MRCC PORT MORESBY VIAEMAIL: ******@****.***.**, TELEPHONE +*** *** ****; RCC AUSTRALIA VIA TELEPHONE +*********** INMARSAT THROUGH LES BURUM (POR ***,IOR***), SPECIAL ACCESS CODE (SAC) **, HF DSC *******
NL BURUM LES 204 4-AUG-2015 03:23:14 773980
AMSA_ER 23150928
PAN PAN
FM JRCC AUSTRALIA 030858Z AUG 15 INCIDENT 2015/5086
AUS4602 CORAL AND SOLOMON SEAS
23FT WHITE BANANA BOAT WITH BROWN STRIPES, AND A 40HP OUTBOARD AND 5 ADULT MALES IS OVERDUE ON PASSAGE FROM LAE (06-44S 147- 00E) TO FINSCHHAFEN (06-36S 147-51E), MOROBE PROVINCE. VESSEL DEPARTED LAE AT 310500Z JUL 15 FOR FINSCHAFFEN WITH ETA OF 310800Z JUL 15 BUT FAILED TO ARRIVE. 
ALL VESSELS REQUESTED TO KEEP A SHARP LOOKOUT AND BE PREPARED TO RENDER ASSISTANCE. REPORTS TO THIS STATION OR MRCC PORT MORESBY VIA EMAIL: *******@****.***.**, TELEPHONE +*** *** ****; RCC AUSTRALIA VIA TELEPHONE +************ INMARSAT THROUGH LES BURUM (POR ***,IOR ***), SPECIAL ACCESS CODE (SAC) **, HF DSC *********, EMAIL: ******@****.***.** OR BY FAX +************.
NNNN
Scientific Research Vessel Drilling - Request for wide clearance 
NL BURUM LES 204 4-AUG-2015 02:29:41 709950
AMSA_ER 23153978
SECURITE
FM JRCC AUSTRALIA 040224Z AUG 15 
AUSCOAST WARNING 202/15
SPECIAL PURPOSE VESSEL JOIDES RESOLUTION CONDUCTING DRILLING OPERATIONS IN POSITION 28 39.80` S 113 34.60` E
2.5NM CLEARANCE REQUESTED.
NNNN
Weather Warning 
PAN PAN
TROPICAL CYCLONE WARNING / ISSUED FOR THE NORTH OF EQUATOR OF METAREA
XI(POR).
WARNING 050900.
WARNING VALID 060900.
TYPHOON WARNING.
TYPHOON 1513 SOUDELOR (1513) 930 HPA
AT 19.9N 133.2E WEST OF PARECE VERA MOVING WEST 12 KNOTS.
POSITION GOOD.
MAX WINDS 95 KNOTS NEAR CENTER.
RADIUS OF OVER 50 KNOT WINDS 80 MILES.
RADIUS OF OVER 30 KNOT WINDS 240 MILES NORTH SEMICIRCLE AND 210 MILES
ELSEWHERE.
FORECAST POSITION FOR 052100UTC AT 20.1N 130.6E WITH 50 MILES RADIUS
OF 70 PERCENT PROBABILITY CIRCLE.
935 HPA, MAX WINDS 90 KNOTS NEAR CENTER.
FORECAST POSITION FOR 060900UTC AT 20.8N 128.1E WITH 75 MILES RADIUS
OF 70 PERCENT PROBABILITY CIRCLE.
935 HPA, MAX WINDS 90 KNOTS NEAR CENTER.

JAPAN METEOROLOGICAL AGENCY.=

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A Tutorial on Decoding NOAA and Meteor M2 Weather Satellite Images in Ubuntu

Recently an RTL-SDR.com reader by the name of Pete wrote in to let us know about a comprehensive tutorial that he has written about setting up NOAA and Meteor M2 weather satellite decoding in Ubuntu Linux with an RTL-SDR.

Pete’s tutorial starts from a fresh install of Ubuntu and uses GQRX, GNU Radio Companion, WxtoIMG and the MeteorM2 decoding tools. He shows how to set up the audio piping within Linux, how to run the MeteorM2 LRPT Offline decoder Windows tool in Wine, a Linux Windows emulator and how to use WxtoIMG together with GQRX.

The NOAA and Meteor M2 weather satellites transmit images that they have taken of the earth. With an RTL-SDR and appropriate antenna you can receive these images. On this blog we have Windows tutorials on receiving NOAA and Meteor M2 satellites.

The Windows LRPTOfflineDecoder tool running in Linux with Wine.
The Windows LRPTOfflineDecoder tool running in Linux with Wine.

A tutorial on using RDS Spy with the SDR# MPX Output Plugin

Over on YouTube user pe1etr has uploaded a tutorial video showing how to set up RDS Spy and SDR# for monitoring RDS. RDS stands for Radio Data System and is a sub carrier added to some FM broadcast signals which carries information such as the station name, the song/programme playing and other data. Although SDR# decodes RDS stations already, a more powerful RDS decoder and monitoring tool is RDS Spy. To get RDS Spy to work with SDR# you need to use a special plugin called MPX Output, which allows SDR# to output audio that includes the RDS subcarrier, which can then be piped via a virtual audio cable to RDS Spy.

Pe1etr’s video shows how to install the MPX Output plugin, how to set it up with virtual audio cable and how to use it with RDS Spy.

Tutorial: Using RDS Spy with the SDR# mpx output plug-in

Creating a low cost Ozone Spectrometer out of RTL-SDR’s to measure mesospheric winds and tides

Over at the MIT Haystack Observatory in Westford Massachusetts, researchers O.B Alam and A.E.E Rogers have been working on creating a low cost ground based Ozone spectrometer out of RTL-SDR dongles (pdf warning). An Ozone spectrometer is used by scientists to measure the concentration, velocity and temperature of the ozone gasses in the mesosphere (50 – 85 km above the ground) and lower thermosphere (85 km+) at the Ozone line frequency of 11072.4545 MHz.

The spectrometer the researchers built consists of a satellite TV parabolic reflector dish with 46.72cm diameter, 9750 MHz LNBF, two Bias Tees, two 740 MHz high pass filters, two 8dB attenuators, a calibration pulse generator, an Intel NUC mini PC and three R820T RTL-SDR dongles.

RTL-SDR based Ozone Spectrometer block diagram from the MIT Haystack Observatory.
RTL-SDR based Ozone Spectrometer block diagram from the MIT Haystack Observatory.
Photo of some of the components of the ozone spectrometer.
Photo of some of the components of the ozone spectrometer.