Tagged: APRS

Lon.TV Demonstrates Decoding Various Digital Signals with RTL-SDR

Tech YouTuber Lon.TV has recently uploaded a video demonstrating how to identify and decode various digital transmissions with an RTL-SDR dongle. In the video he explains how to use VB Cable to pipe audio from SDR# into various decoders, and then goes on to show DMR, APRS, POCSAG, L-Band AERO, FT8, and JS8/JS8CALL all being decoded via an RTL-SDR Blog V3 dongle.

Software Defined Radio Part 2 - Decoding Digital Transmissions with an RTL-SDR USB Radio

Radio Related News Occurring in the Russia-Ukraine Conflict

In the current Russia-Ukraine conflict we've seen several noteworthy radio related events occurring over the last few days, mostly throughout Twitter.

Russian HF Bomber Communications

As mentioned in the previous post it has been found that since the start of the invasion, Russian Strategic bombers have been very active on USB voice at 8131 kHz. We've even seen a security firm predict air raid siren activations based on increased bomber HF activity. 

Russian Military HF Frequencies Jammed by Activists

It has been observed that several Russian military HF stations including the famous UVB-76 Buzzer have been jammed with either the Ukrainian national anthem, or various meme-type songs. It is likely that these stations are being jammed mostly by civilian activists, or members of the activist hacker collective known as Anonymous, rather than any military organization.

The UVB-76 Buzzer is a famous and mysterious numbers station that plays a buzzing sound and sometimes voice. It can be received from all over the world. Via civilian investigations, and through the use of the KiwiSDR TDoA direction finding functionality, it has been found to be transmitted from a location just north of St. Petersburg, and is assumed to be a military signal of some sort.

We've also seen waterfall text based jamming:

Using KiwiSDRs you can listen to these jammed stations yourself remotely through public internet connected SDRs in Europe. Some known frequencies are listed here and here

We note that there have also been reports about fake Russian frequencies being posted on the internet.

We assume most jamming is happening from outside the warring countries, and it is unknown how far the jamming signals extend onto Russian or Ukrainian territory, or how much of an impact they are having on Russian operations.

Russian State TV Hacked

Twitter account Anonymous TV has reported hacking Russian state TV to show citizens what is actually happening in Ukraine. It's unknown if this was a hack via TV transmissions being overpowered by another signal, or a computer hack.

Starlink Activated in Ukraine

A few days ago Elon Musk and SpaceX activated their Starlink wireless satellite internet system in Ukraine, and have sent over a shipment of ground terminals. This is useful as even if the local wired internet were to be destroyed, or be censored by Russia, the Starlink system will be able to connect to uncensored internet as long as there is power. 

An account of a Ukrainian engineer and RF hobbyist recently Tweeted his success at getting his Starlink system up and running from his home in Ukraine. We decided not to link to his Twitter account in this post, just in case he needs to delete his account for safety in the future as he appears to be very close to the bombing.

Viasat Satellite Service Experiences Cyberattack and Outages

Viasat, another provider of satellite internet services in Ukraine region appears to have been subject to a DDOS cyberattack, causing outages to it's satellite internet service in the European region.

SSTV Activism Seen On Russian Meridian Satellites

Meridian satellites are a "family of telecommunications satellites for civil and military use developed by Russia in the 2000s placed in a Molniya Orbit" (Wikipedia). A tweet by Scott Tilley @coastal8049 has noted that they have seen reports of SSTV activist activity occurring on the 484 MHz Meridian transponders. 

Scott Tilleys Twitter feed also shows some interesting other pieces of news and information, including frequencies and orbits of Meridian satellites, images of a destroyed Russian command and control satellite communications vehicle, and links to now deleted, but Google cached pages with information about Russian satellite communication systems.

APRS Activism against Russia causes APRS-IS DDOS

Amateur radio operators can use a system called APRS to communicate with text and packet data globally through internet connected radio repeaters. A few days ago it appears that anti-Russia activists flooded the APRS-IS (Automatic Packet Reporting System-Internet Service) system with bogus packets targeting Russian coordinates, which unintentionally resulted in a denial of service (DOS) event on APRS trackers like aprs.fi

DARC Urges Safety First for Ukraine and Foreign Amateur Radio Hobbyists

The German ham-radio association known as DARC has issued a warning to Ukrainian hams, and to foreign hams who may receive from them. Amateur radio operations are currently banned in Ukraine due to wartime laws.

Poland Amateur Radio Society Provides WinLink HF Email Service

In response to geopolitical threats, the Poland Amateur Radio Society has set up a HF WinLink email system, aimed at provided email services to amateur radio operators that could be cutoff from internet email services. It appears this may be aimed at helping Ukrainians communicate, however in these modern days of electronic warfare, it is important to take into account the warning from DARC above too as transmitting stations could easily be located by Russian electronic warfare forces.

Dear HAM operators, in the face of the latest threats in our region and a possibility of an incoming wave of refugees, with over 2 mln already living in Poland, we would like to remind you that we are at your disposal.

If you are a licensed amateur radio operator, you can send information by e-mail to your relatives in Poland or Emergency Services with via the Winlink system, which works on HF bands, independently of access to the local ICT infrastructure https://winlink.org/WinlinkExpress.

We advise you to download the software, install it and check its operation.
Polish WinLink nodes are QRV on 160,80,20m
SR5WLK dial frequency 3595,5 kHz USB
SR3WLK dial requency 14111 kHz USB
SP3IEW dial frequency 1865 kHz USB

If we receive information about the cut-off of the Internet in the region in danger, we will be QRV daily as SP0MASR @ 18-20 UTC on the frequencies 3770 kHz +/- QRM, 7110 kHz +/- QRM. In such a situation, please communicate in Polish or English.

We are here to serve you.

Shortwave Listening Updates

The excellent SWLing.com blog has also provided some updates on shortwave, including news that WRMI have resumed broadcasts of Radio Ukraine International, Ukrainian state radio resumes broadcasting at 549 kHz, and that the BBC adds to new broadcasts to Ukraine.

Russian Oligarch Jets Tracked with ADS-B

An activist has set up a Twitter account to track the private jets of Russian Oligarch's via ADS-B. ADS-B aircraft data can be used to track aircraft locations, and these signals are typically received with low cost SDRs like RTL-SDRs. The project appears to use data sourced from adsbexchange.com which is known to be one of the only ADS-B aggrators that does not censor data.

The 7055 kHz 'Radio War' Frequency Sees Increase in Activity

In has been reported that the 7055 kHz LSB amateur radio frequency has been used by Ukrainian and Russian amateur radio operators for some time now to insult each other in a 'radio war', and recently activity has significantly increased. Other frequencies involved include 7050 kHz LSB and 3731 kHz.

Captured Equipment Shows Russian Radio Hardware In Use

A recent tweet shows a photo of hardware supposedly captured from Russian forces. Of interested is a Russian R-187PI Azart, a handheld digital software defined radio.

At the same time unconfirmed reports suggest that some parts of the Russian army may be relying on civilian Baofeng radios.

An APRS Tracker with HackRF, WebUSB and WASM

Thank you to Radoslav Gerganov for writing in and submitting news about the release of his open source web-based APRS tracker named "aprs-sdr". The web based software turns a HackRF device into a mobile APRS beacon.

Most interestingly the software works via the WebUSB interface, which allows for USB devices like a HackRF SDR to connect directly to the software through USB via the Chrome web browser. So no external app or software needs to be downloaded, all you need to do to run the code is open the hosted aprs-sdr page at https://xakcop.com/aprs-sdr with a Chrome browser, and connect the HackRF to your device.

Radoslav writes further:

The tracker is using the HTML Geolocation API to fetch the device’s location and WebUSB to talk with the SDR. The code which generates the packets is written in C++ and compiled to WASM. You can find the source at https://github.com/rgerganov/aprs-sdr.

And now to some results. I have successfully transmitted packets from my home to LZ0DOE (15km away!) using my Pixel phone, HackRF and ANT500. I find it amazing given the low TX power of HackRF.

Radoslav also notes that in the future he hopes to add other SDRs as well. He also notes that the script seems to work best on desktop Chrome. On mobile Chrome there may be a bug which stops transmission after a few packets.

Using the aprs-sdr WebUSB application.

SDRAngel Features Overview: ADS-B, APT, DVB-S, DAB+, AIS, VOR, APRS, and many more built-in apps

SDRAngel is a general purpose software defined radio program that is compatible with most SDRs including the RTL-SDR. We've posted about it several times before on the blog, however we did not realize how much progress has occurred with developing various built in plugins and decoders for it.

Thanks to Jon for writing in and sharing with us a demonstration video that the SDRAngel team have released on their YouTube channel. From the video we can see that SDRAngel now comes stock with a whole host of built in decoders and apps for various radio applications making it close to an all-in-one SDR platform. The built in applications include:

  • ADS-B Decoder: Decodes aircraft ADS-B data and plots aircraft positions on a map
  • NOAA APT Decoder: Decodes NOAA weather satellite images (in black and white only)
  • DVB-S: Decodes and plays Digital TV DVB-S and DVB-S2 video
  • AIS: Decodes marine AIS data and plots vessel positions on a map
  • VOR: Decodes VOR aircraft navigational beacons, and plots bearing lines on a map, allowing you to determine your receivers position.
  • DAB+: Decodes and plays DAB digital audio signals
  • Radio Astronomy Hydrogen Line: With an appropriate radio telescope connected to the SDR, integrates and displays the Hydrogen Line FFT with various settings, and a map of the galaxy showing where your dish is pointing. Can also control a dish rotator.
  • Radio Astronomy Solar Observations: Similar to the Hydrogen line app, allows you to make solar measurements.
  • Broadcast FM: Decoding and playback. Includes RDS decoding.
  • Noise Figure Measurements: Together with a noise source you can measure the noise figure of a SDR.
  • Airband Voice: Receive multiple Airband channels simultaneously
  • Graves Radar Tracker: For Europeans, track a satellite and watch for reflections in the spectrum from the French Graves space radar. 
  • Radio Clocks: Receive and decode accurate time from radio clocks such as MSF, DCF77, TDF and WWVB.
  • APRS: Decode APRS data, and plot APRS locations and moving APRS enabled vehicles on a map with speed plot.
  • Pagers: Decode POCSAG pagers
  • APRS/AX.25 Satellite: Decode APRS messages from the ISS and NO-84 satellites, via the built in decoder and satellite tracker.
  • Channel Analyzer: Analyze signals in the frequency and time domains
  • QSO Digital and Analog Voice: Decode digital and analog voice. Digital voice handled by the built in DSD demodulator, and includes DMR, dPMR and D-Star.
  • Beacons: Monitor propagation via amateur radio beacons, and plot them on a map.

We note that the video doesn't show the following additional features such as an analog TV decoder, the SDRAngel "ChirpChat" text mode, a FreeDV decoder and several other features.

TechMinds: OpenWebRX Feature Overview And Raspberry Pi Setup

Over on YouTube TechMinds has posted his latest video which shows an overview of the features available in OpenWebRX, and also how to set it up on a Raspberry Pi. OpenWebRX is software which allows you to access your SDR remotely via the internet or local network through a web browser. All major SDRs are supported including RTL-SDRs. The software includes a waterfall display, all the standard demodulators, as well as several digital decoders for DMR, YSF, NXDN, D-Star, POCSAG, APRS, FT8, FT4, WSPR, JT65 and JT9.

In the video TechMinds first demonstrates OpenWebRX in action, showing reception of HF SSB amateur radio signals, decoding FT8 and plotting received grids on a map, decoding and plotting APRS on a map and decoding YSF/DSTAR/DMR digital voice. After this demonstration he goes on to show how to set up the OpenWebRX server on a Raspberry Pi via the installation image.

OpenWebRX Feature Overview And Raspberry Pi Setup

Creating an APRS I-Gate and Digipeater with Baofeng and RTL-SDR

Over on YouTube ModernHam has uploaded a video showing how to create an APRS I-Gate and Digipeater with Baofeng and RTL-SDR. He also makes use of a Raspberry Pi as the computing module and an audio cable to connect the Baofeng to the audio jack of the Pi. The tutorial then consists of a walk through of the various software setup steps, and finally how to connect the Baofeng and RTL-SDR to the Pi.

If you weren't already aware, Automatic Packet Reporting System (APRS) is a digital VHF mode used in amateur radio. It allows for packets of data to be sent to receiving nodes over a local area via RF. Typical uses for it are vehicle tracking, weather station telemetry, text messages, announcements and other wireless device telemetry like high altitude balloons. An I-Gate is an internet connected node which receives local APRS RF signals and uploads them to the internet, to be seen on sites like aprs.fi. TX capable I-Gates may also broadcast to the local RF network messages from APRS transmitters on the other side of the world.

APRS I-Gate and Digipeater with Baofeng and RTL-SDR

IGate2: An RTL-SDR Compatible APRS iGate for Android

Thank you to Agrosi Luciano for submitting news about his new RTL-SDR compatible Android App called "IGate2". IGate2 is a receive only APRS IGate written for Android devices. There is a free and paid version of the app. The free version is limited to 100 packets forwarded per session. The paid version costs US$3.49 and has unlimited packet forwards. The description of the app is pasted below:

The RTL-SDR dongle tuner (cost starting from 10 €) and its antenna, receives the information contained in APRS packets transmitted from HAM radio stations, and then a phone device, with IGate2, forwards them to the world wide web using its internet connection (WiFi or 3G).

IGate2 acts as a Software Defined Radio Demodulator, a TNC Modem and an Internet Gate.

It needs the installation of a driver (Martin Marinov’s driver) for the SDR dongle that you can find in: https://play.google.com/store/apps/developer?id=Martin+Marinov.

If you already own an unused cellular phone or tablet, IGate2 represents a very cheap, compact and easy-to-use solution for suppling an IGATE service to radio amateur community.

Raw data contained in radio packets are visible on the phone screen and may be routed (if you check this option) to the APRS-IS network. All data convoyed and shared in APRS-IS network can be seen in maps and bulletins on particular websites, for example: http://aprs.fi/ .

To be authorized to send data to APRS-IS you must have a HAM CallSign and a PassCode. See aprs-is.net. If you are not a radio amateur, you may only use your equipment in receive only mode.
The app has an audio monitor useful for tuning the parameters of the Sdr receiver (it may not work well in old devices with low memory). In the main page there is a frequency switch, a hub with the text of received packets, two indicator lights: one for the Sdr connection and one for the Aprs-Is connection, three counters reporting the number of: received, forwardable and forwarded packets. When you leave the main page while the IGate is running, the app service will continue working in the background, you can recall the main page by tapping the service icon in the android status bar.

Since the device and the Sdr dongle drains much power from the phone battery, it is recommended to use the phone charger or a power bank. You will need an OTG power cable. It is not easy to find a working cable, maybe you can do it yourself. The reception quality of the IGate depends, above all, on the antenna connected to the Sdr dongle. With very strong FM broadcasts in your area, it may be helpful to manually adjust the gain of the receiver or use a band-stop filter.

If you weren't already aware, Automatic Packet Reporting System (APRS) is a digital VHF mode used in amateur radio. It allows for packets of data to be sent to receiving nodes over a local area via RF. Typical uses for it are vehicle tracking, weather station telemetry, text messages, announcements and other wireless device telemetry like high altitude balloons. An IGate is an internet connected node which receives local APRS RF signals and uploads them to the internet, to be seen on sites like aprs.fi. TX capable IGates may also broadcast to the local RF network messages from APRS transmitters on the other side of the world.

IGate2: Android App that turns your phone and RTL-SDR into an APRS IGate.
IGate2: Android App that turns your phone and RTL-SDR into an APRS IGate.


PyPacket: An APRS iGate For Your RTL-SDR

[Pypacket] was developed by GitHub user [cceremuga] and allows you to take advantage of a Linux computer (such as a Raspberry Pi) and an RTL-SDR to quickly and easily build your own APRS iGate.

For those not familiar with APRS, it stands for the [Automatic Packet Reporting System] and is used by amateur radio operators for applications like transferring messages and location data over RF networks and the internet. The internet connection is where an iGate comes into play. An iGate is used to connect an APRS RF network to the internet, so that many isolated RF APRS networks can communicate worldwide. Furthermore this software can be configured as a “SatGate”, which like an APRS iGate will take messages from APRS satellite’s and route them over the internet.

For example, you could have an amateur radio vehicle continually transmitting it’s location via RF to an APRS iGate. The vehicles position can then be viewed online on an APRS aggregation site like aprs.fi, or it could be re-transmitted over RF elsewhere in the world.

An iGate is usually accomplished by using a ham radio tuned to the local APRS frequency (or sat frequency) and then special PC software is configured to gate the messages.  However, with the release of PyPacket the amount of work and cost required to setup an iGate has been cut drastically.