Category: RTL-SDR

ADS-B On Android App Now Supports 978 MHz FIS-B NEXRAD Weather and Traffic

The “ADS-B on Android” app has been updated and now supports the reception and display of 978 MHz UAT FIS-B Weather and Traffic data. The app also receives ADS-B data as per normal. To use the app you will need an RTL-SDR dongle and a USB OTG cable.

UAT stands for Universal Access Transceiver and is a protocol similar to ADS-B that is used mainly by smaller aircraft in the USA. UAT has some extra features for pilots compared to ADS-B. In addition to location information UAT provides a Traffic Information Service (TIS-B) which allows pilots in the air to see what ground control sees on their traditional RADAR system. It also provides a Flight Information Service-Broadcast (FIS-B) which includes NEXRAD weather data and other information. NEXRAD is an array of ground station weather radars that are used to provide pilots with accurate maps of precipitation and wind.

The free version of the app has ads and does not display NEXRAD weather radar on the default map. The pro version removes the ads and allows you to display a NEXRAD overlay on the map. It costs $2.50 USD.

Free Version: https://play.google.com/store/apps/details?id=com.wilsonae.android.usbserial

Pro Version: https://play.google.com/store/apps/details?id=com.wilsonae.android.usbserial.pro

NEXRAD FIS-B precipitation data displayed on map.
NEXRAD FIS-B precipitation data displayed on map on the pro version of “ADS-B On Android”

 

New product from FlightAware: A 1090 MHz Bandpass Filter for the RTL-SDR

FlightAware.com have released a new 1090 MHz bandpass filter that is intended for use with the RTL-SDR. FlightAware.com is a website that aggregates ADS-B aircraft location data from various contributors. The contributors are often users with RTL-SDR dongles running their PiAware software. By contributing to their service you gain access to their premium services for free.

The bandpass filter is available on Amazon for US customers for $19.95 USD and on eBay worldwide for $24.95 USD. This is the cheapest ADS-B filter we’ve seen yet. It comes in a metal case with SMA connectors, passes 980 MHz – 1150 MHz, has an insertion loss of about 1.65 dB at 1090 MHz and has about a 40dB drop outside the pass band. Over on their forums many users are reporting good results.

A bandpass filter blocks all frequencies apart from the range you are interested in, significantly reducing the effects of out of band interference. It is especially useful if you live near cell phone towers as these can easily interfere with the 1090 MHz frequency. 

FlightAware also sell an ADS-B antenna on Amazon for $44.95 USD and worldwide on eBay for $54.99 which may be of interest to some people.

An alternative ADS-B filter for the RTL-SDR is the one made by Adam 9A4QV. Adams filter uses LTCC filter technology which gives lower insertion loss, but a less sharp cutoff.

The FlightAware 1090 MHz ADS-B Filter
The FlightAware 1090 MHz ADS-B Filter
Filter Reponse Test Data
Filter Reponse Test Data

Frequency Manager Suite Plugin for SDR#

Recently the popular Frequency Manager + Scanner plugin set for SDR# has been upgraded and renamed to the “Frequency Manager Suite”. The plugin can be downloaded from their new website at www.freqmgrsuite.com. The plugin suite includes a frequency scanner and manager, a scanner metrics recorder, a scheduler, an activity logger and a frequency entry plugin.

Apart from plugins the suite also now includes a plugin manager program called “Pluginator” which can help you to install and delete plugins without needing to edit the Plugins.xml file directly. There is also a new database manager tool which can help you to import frequency databases from online or other sources.

We have posted the full feature release below:

The Frequency Manager Suite (FMS) adds 4 more plugins to the previous set of 3:

  • Scheduler – allows you to schedule listening activities by date and time.

  • Activity Logger – records scanner activity to a file for later use.

  • Scanner Decisions – now a first-class plugin and also available as the classic stand-alone window. And you can change the position of the plugin without restarting SDR#.

  • Frequency Details – displays details about a frequency from your database. And you can change the position of the plugin without restarting SDR#.

New standalone applications also come with FMS:

  • Data Tools – this significantly upgraded import/export application lets you import data from 6 popular internet databases as well as generically-formatted files, and permits you to export your FMS databases to standard file format.
  • The Pluginator – an application that lets you add, delete, and change the order of plugins without ever having to hand-edit the SDR# file Plugins.xml. Just fill in the blanks.

New features in Frequency Manager + Scanner:

  • The new Preferences dialog allows customization without hand-editing a configuration file.
  • FMS configurations are now kept in a file separate from those of SDR#, permitting easier upgrades to SDR#.
  • You can have multiple frequency databases, and can change to a different database without restarting SDR#.
  • When tuning manually you can optionally change the radio settings (mode, BW, etc.) according to what’s in the database for the tuned frequency.
  • Scan resolution – high-res or low-res to favor speed over accuracy or vice versa.
  • Adjacent Frequency Rejection now displays its bandwidth on the spectrum analyzer.
  • Plus many other improvements and bug fixes.

fms_1v2   fms_3   fms_2   

pluginator

Detecting Pulsars (Rotating Neutron Stars) with an RTL-SDR

The RTL-SDR has been used for some time now as an amateur radio astronomy tool. Radio astronomers Peter W East and GM Gancio have recently uploaded a paper that details their experiments with detecting Pulsars with an RTL-SDR (doc file).

A pulsar is a rotating neutron star that emits a beam of electromagnetic radiation. If this beam points towards the earth, it can then be observed with a large dish antenna and a radio, like the RTL-SDR. The abstract of the paper reads: 

This project sought to determine the minimum useful antenna aperture for amateur radio astronomers to successfully detect pulsars around the Hydrogen line frequency of 1420MHz. The technique relied on the collaboration with GM Gancio, who provided RTL SDR data of the Vela pulsar (B0833-45, J0835-4510) and others, collected with a 30m radio telescope. This data was processed to determine the achievable signal-to-noise ratio from which, the minimum useful dish size necessary for some effective amateur work, could be calculated. Two software packages were developed to do synchronous integration, a third to provide a power detection function and a fourth for spectrum analysis to recover pulsar rotation rate.

With their system the authors were able to detect and measure the rotation period of the Vela pulsar. Also, from their data they were able to estimate that the minimum dish aperture required to observe the Vela pulsar would be 6m, noting that the Vela pulsar is probably the strongest pulsar ever detected. They also write that by utilizing 5 RTL-SDRs to gather 10 MHz of bandwidth together with some processing that the minimum required dish aperture could be reduced to 3.5m.

The Vela pulsar pulse power integrated over a 50 second 100MB file, combining some 560 pulsar pulses
The Vela pulsar pulse power integrated over a 50 second 100MB file, combining some 560 pulsar pulses.

In addition to these Pulsar experiments, Peter has also uploaded new papers about improving his Hydrogen Line RTL-SDR Telescope (pdf), and has updated his paper on improving the frequency stability of RTL-SDR’s with air cooling (doc file). Peter found that the frequency stability of the RTL-SDR (with standard oscillator) could be significantly improved by adding heat sinks and aircooling them. The graph from his paper below summarizes his results.

Results from air cooling the RTL-SDR.
Results from air cooling the RTL-SDR.
The air cooled and heatsinked RTL-SDRs
The air cooled and heat sinked RTL-SDRs

All of Peters papers can be found on his website at y1pwe.co.uk/RAProgs/index.html. He has many RTL-SDR radio astronomy related resources there, so check it out if you are interested.

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.