Tagged: APRS

TechMinds: Receiving and Decoding Packets from the GreenCube Cubesat Digipeater

GreenCube is a CubeSat by the Sapienza University of Rome, and it is designed to demonstrate an autonomous biological laboratory for cultivating plants onboard a CubeSat.

While this is an interesting mission in itself, for amateur radio operators there is another interesting facet to the satellite. Unlike most CubeSats which are launched in Low Earth Orbit (LEO), GreenCube was launched higher in Medium Earth Orbit (MEO) which provides a larger radio reception footprint over the earth. The satellite also contains a digital repeater (digipeater) at 435.310 MHz, which allows amateur radio operators to transmit digital radio packets up, and have the satellite repeat the packet back over a wide area footprint on earth. 

Over on his latest video, Matt, from the TechMinds YouTube channel shows us how to receive and decode the packets from the GreenCube digipeater. In his demonstration Matt uses an SDRPlay RSPdx as the receiver, SDR++ as the receiver software, SoundModem as the packet decoder, GreenCube Terminal for displaying the messages, and GPredict for tracking the satellite and compensating for the doppler effect. He also notes that while a directional antenna on a motorized tracker is recommended, he was able to still receive packets with his omnidirectional terrestrial antennas without much issue.


The US Air Force may have shot down an Amateur Radio Pico Balloon over Canada

Since the famous takedown of a suspected Chinese spy balloon, US jets have shot down a total of three more unidentified balloon objects, now suspected by officials to be 'commercial or benign'. There is speculation that at least one these three objects may have been an amateur radio 'pico' balloon.

One part of the amateur radio hobby is launching high altitude balloons with various radio and other payloads. Larger amateur radio balloons launched in the USA require FAA clearance, need a radar reflector attached, and usually continually transmit APRS telemetry before naturally popping and falling back to earth after a few hours, just like a weather balloon.

However there is also the simpler 'pico' ballooning hobby, which involves the use of mylar helium party balloons to launch small solar powered payloads that are only a few grams in weight. They typically transmit low power WSPR at HF frequencies and can only transmit whenever there is sufficient solar power available. Amateur radio or SDR hobbyist stations around the world can pick up these transmissions, and report them on amateur.sondehub.org and/or wsprnet.org. Well built balloons can totally circumnavigate the globe several times over several months before degrading.

While termed 'pico', the party balloons used can still be roughly a meter in diameter on the ground, with some latex balloons potentially expanding further at high altitudes due to the low atmospheric pressure. These balloons can be legally launched from almost anywhere in the world. In particular in the USA there is no FAA clearance required to launch them due to their payload being much less than the limit of 4 lbs (1.8kg). 

32" Silver Orb Shaped Mylar Balloon used for Pico Ballooning
32" Silver Orb Shaped Mylar Balloon used for Pico Ballooning

There is speculation that at least one of the objects shot down over Canada, Yukon by a US Air Force jet may have been amateur radio pico balloon K9YO-15 which was launched from Illinois on October 10 2022. It was on it's seventh circumnavigation of the globe after being aloft for 123 days.

The launch blog post indicates that the K9YO-15 balloon was flying a silver mylar 32" sphere SAG balloon which appears to be this one from balloons.online. Unlike latex or rubber weather balloons which inflate and stretch as they rise into lower atmospheric pressures, these mylar balloons can't stretch, so their fully inflated ground size will be the same as their size at high altitudes, meaning the pico balloon won't get much bigger than 32". The payload was a GPS module, Arduino, SI5351 used as a WSPR and APRS transmitter and a solar panel, all together weighing 16.4 grams. A pentagon memo notes that the object shot down over Canada was a "small metallic balloon with a tethered payload" which fits the description of the pico balloon exactly.

The K9YO Pico Balloon Payload
The K9YO-15 Pico Balloon Payload
An (unrelated) Example Amateur Radio Pico Balloon Launched by a Naval Academy
An (unrelated to this story) example Amateur Radio Pico Balloon launched by a Naval Academy (Source: http://www.aprs.org/balloons.html)

The K9YO-15 balloon ceased all WSPR telemetry transmissions while flying just below Alaska since Feb 11 00:18 UTC (just before sunset in Alaska when the solar panels would stop working).

By using NOAA wind models and the last known location by Alaska, K9YO-15 was projected to have been over Yukon when the US Air Force shot down the unknown balloon object at Feb 11 20:41 UTC (3:41 PM EST / 1:41 PM Yukon time according to Canadian Defense Minister Anand). Reports put the altitude of the shot down object at approximately 40,000ft (~12000 meters), which matches the projected ~11500 meters of K9YO-15. Based on the previous days transmission times, it is suspected that if it were operational, the balloon would have begun transmitting again sometime later in the Yukon afternoon when the sun was stronger, but no transmissions have been seen.

On February 14th the balloon was declared as missing in action by the launch group. 

K9YO projected location at the time the object was shot down.
K9YO projected location at the time the object was shot down.

The search area for the fallen balloon debris is reported to be in difficult to access terrain between Dawson City and Mayo. If we do a rough overlay of the predicted trajectory over a Google map, we can see that the predicted location of KY9O-15 at the reported time of the missile impact matches this description very well.

Rough trajectory overlay
Rough trajectory overlay

Over on Twitter @ikluft (KO6YQ) has been reporting on this speculation, and has been keeping an eye on K9YO-15, awaiting telemetry transmission. We recommend following his account for further updates.

Twitter user and ex project Google Loon engineer @BalloonSciDan has also speculated that the objects shot down may have been pico balloons.

Over on Reddit @ikluft (KO6YQ) has also written some insightful information:

I see you're all talking about my tweet. Yes, we are still watching to see if K9YO-15 transmits any telemetry today.

So far K9YO-15 has not sent any new telemetry since Friday before sunset over Alaska. Some have misread confusing data presentation on Sondehub which lists last known telemetry as covering a time range from then to now. Currently the last we've heard from K9YO-15 was Friday Feb 10 before sunset over Alaska (00:48 GMT Feb 11). But the map on Sondehub does show the last reported position.

These floater balloons often use only solar panels, no batteries. Batteries were dropped from the projects early on because they have limited charging cycles before they stop accepting a charge, especially in the harsh temps at altitude, -40F/-40C or worse. When the battery stops accepting a charge, it ends telemetry from the mission. So they only report telemetry during daylight, when the sun is at a high enough angle to illuminate the tiny solar panels. In the Arctic winter, the days are short and the sun might not get high enough to wake up the electronics. So it stays dormant for one or more days until it drifts back down to lower latitudes where there's more sunlight. So K9YO-15 was in a period where watchers didn't expect to hear from it for a few days. But we expected it today. So far nothing. As I write this, daylight is almost done way up there for Tuesday, Feb 14.

We (the Amateur Radio balloon community) only expect any telemetry from it today would be via WSPR, none via APRS. WSPR uses HF and can be received at long distances, where it's relayed to Internet map sites. APRS is (usually) on VHF and UHF, only received by line of sight. There are no relay stations in range of today's projected flight course in northern Ontario and James Bay, Canada. So APRS-fed sites wouldn't show updates today anyway.

The club in Illinois that built the balloon has tracking links at https://nibbb.org/links-to-locate-and-track/ - you'll have to scroll down to find K9YO-15.

For an introduction, I'm Ian KO6YQ. I was involved in the first Ham Radio balloons that circumnavigated the globe starting in 2016, launched from San Jose, California. I had roles on them including tracking analyst and social media spokesman. I also organized and led the Ham Radio tracking teams which recovered the Civilian Space eXploration Team (CSXT) first amateur rocket to (suborbital) space in 2004.

Explaining a discrepancy with time reporting on Sondehub, KO6YQ notes:

Time has run out for solar power to provide any telemetry on Wednesday, February 15. So far, no new data. For those who were confused by it, remember that Sondehub has problematic data presentation so don't use it for anything other than mapping the last known position. A reliable place to check for K9YO on WSPR is the WSPR Spots: https://www.wsprnet.org/olddb?mode=html&band=all&limit=200&findcall=k9yo&findreporter=&sort=date

Frequently asked Questions (FAQ):

Since this story has gone viral and now entered the mainstream media, we thought we'd answer a few common questions that we're seeing in the media and comments.

Who is launching pico balloons and why?

Pico balloons are typically launched by ham/amateur radio hobbyists, universities, researchers, schools or kids STEM programs. The idea of launching a low cost balloon that can be tracked while travelling the world is a fun project for hobbyists and a great STEM learning experience for kids.

You can track other currently active pico and larger amateur radio balloons at https://amateur.sondehub.org/.

You might also be interested in tracking regular weather balloons which are launched by meteorological agencies around the world usually twice per day. These are designed to only last a few hours in the air before popping. They can be tracked at https://sondehub.org. A popular hobby of radio enthusiasts is chasing these weather balloons and being the first to recover the fallen sensor package called a radiosonde.

A pico balloon is essentially a kids party balloon. Why aren't there thousands of kids party balloons circumnavigating the globe? 

Balloons will inflate more as they rise into the atmosphere, since higher altitudes have lower pressure. A kids party balloon would typically be inflated fully on the ground. If a careless child released a balloon it would rise up, and pop within a few hours, as it reaches an altitude of around 5000ft - 30,000ft (1500m - 9000m) or higher where the internal pressure of the balloon is too great for the balloon's material to hold it.

Pico balloons are weighted by their payloads, and are only partially inflated on the ground. The goal is to inflate with enough Helium or Hydrogen to get the payload to rise at ground level, but allow enough internal space for the balloon to expand without popping as it rises. The weighted balloon will eventually reach an equilibrium point at some altitude where it's fully inflated, but can't rise any higher due to the weighting. This is called being 'neutrally buoyant'. The balloon launcher can use a calculator (such as this one) to determine the right amount of helium to use based on the balloon size and payload weight.

Mylar balloons are used because helium atoms will leak out of the walls of latex/rubber balloons, and they will be flat within a few days. With Mylar balloons the leakage is much slower and they can stay inflated for months.

How can a pico balloon circumnavigate the globe?

As mentioned in the previous question, it's possible to engineer the height that the balloon will fly at by only partially inflating the balloon on the ground. Once at the desired altitude, winds will eventually pull the balloon into global jet streams that take the balloon all around the earth at an average speed of 80 - 140 mph (129 - 225 km/h).

A website like Ventusky can be used to view the current jet streams at 40,000ft (12,000m), the altitude that KY9O-15 was neutrally buoyant at. 

Are pico balloons legal?

In the USA the regulations defined in PART 101 - MOORED BALLOONS, KITES, AMATEUR ROCKETS, AND UNMANNED FREE BALLOONS are only applicable to larger balloons. Small balloon payloads are exempt from these regulations. Similar exemptions exist in most countries.

In California helium balloons in general have been banned, to stop pollution, damage to wildlife, and to protect power lines. 

The transmission of the WSPR and APRS telemetry radio signals would be allowed under amateur radio rules. UK, Yemen and North Korea are countries that prohibit transmissions from balloons, and compliance can be achieved via geofencing the transmissions in the software.

All information suggests that the NIBBB hobby club and KY9O's balloon were operating perfectly legally. 

What exactly was the payload on the KY9O-15 pico balloon?

The payload was a GPS receiver, an Arduino microcontroller, a radio transmitter and some solar panels. The solar panels power the electronics when in sun, and the GPS receiver determines the global coordinates of the balloon. The microcontroller is the 'brain' of the payload which reads the GPS coordinates from the GPS receiver, and tells the transmitter to send out a WSPR radio signal advertising the balloons ID and coordinates.

These are all common off the shelf, small components that could all fit in the palm of a hand. They would in total cost under $100. K9YO's payload in total only weighed 16.4g (0.58 oz). 

An F22 with all it's radio sensors should have picked up the transmissions from the pico balloon. Why didn't it?

Pico balloons usually don't carry batteries because they are heavy and degrade over time. So instead they carry paper thin solar panels. So the balloon circuits and transmitter are only active when in strong sunlight, any other time it is completely quiet and powered down. It's possible that in the weak Yukon sun at high latitude wouldn't have been strong enough to power the WSPR transmitter until later in the day.

How could a tiny 32" balloon be spotted by radar? How could a sidewinder missile lock onto it?

The pico balloon was made out of metallic mylar material which would easily show up on a modern radar system. It's possible that in the past before the Chinese spy balloon incident, radar operators would ignore or filter out slow moving small objects like insects/birds/balloons that pose no threat.

The sidewinder has a fragmentation warhead, so an explosion near the balloon would easily take it out. The metallic mylar material would easily reflect the sun's infrared, and against the cold background of the sky/space it would be easy for the IR heat seeker sensor on the sidewinder missile to track it. 

The K9YO balloon was flying at altitudes used by commercial airliners. Is there any risk to them?

A jet coming across a pico balloon in the first place would be very unlikely, and even more unlikely for it to make it's way in to an engine even if an aircraft flew directly at it. But there is some risk that a balloon ingested by an jet engine could cause issues. However given their lightweight nature it seems unlikely that there would be any massive damage, if any at all.

What is WSPR and APRS?

WSPR (pronounced as 'whisper') stands for Weak Signal Propagation Reporter. It is a type of radio signal protocol used by amateur radio hobbyists. Because of the way it is designed, it is possible for WSPR to be transmitted with very low power (such as the tiny amount of power possible from small solar panels), and still be received by amateur radio ground stations all over the world. The WSPR signal encodes it's callsign ID, and the transmitters GPS location. Amateur ground stations will upload received WSPR data to sites like wsprnet.org.

APRS or "Automatic Packet Reporting System" is another protocol used by amateur radio hobbyists. However, these signals don't travel globally, rather they can only be received locally with line of sight. The advantage is that APRS signal can be transmitted much faster (assuming sufficient power).

Are we 100% certain that the object was the K9YO pico balloon?

No, despite the circumstantial evidence, there is still some doubt. The balloon was already old and probably near the end of it's life. The sun in the high Yukon latitudes is also weaker, meaning that the solar panels might not be getting sufficient sun to power the circuits. The balloon had previously gone missing for 30 days before reappearing. And the transmitter was showing signs of drifting in frequency.

Are there any other globe trotting radio projects?

Yes, there are small autonomous boats or 'drift buoys' travelling the seas through natural currents. These also use WSPR and APRS to report their location. hitchBOT was a hitchhiking robot that relied on travelling strangers to find and carry it around the world. It had a GPS receiver and 3G radio.

SDRangel Now Available on Android: Mobile ADS-B, AIS, APT, Digital Voice, POCSAG, APRS, RS41 Radiosonde Decoders

SDRangel is a free open source software defined radio program that is compatible with many SDRs, including RTL-SDRs. SDRAngel is set apart from other programs because of it's huge swath of built in demodulators and decoders.

Thank you to reader Jon for writing in and noting that SDRangel has recently been released for Android as a free Google Play download. This is an amazing development that could open up many doors into portable decoding setups as the Android version supports almost every decoder implemented on the desktop version. Jon writes:

It includes most of the functionality of the desktop version of SDRangel, including:

  • AM, FM, SSB, Broadcast FM and DAB, AIS, ADS-B, Digital Voice (DMR, dPMR, D-Star, FreeDV), Video (DVB-S, DVB-S2, NTSC, PAL), VOR, LoRa, M17, Packet (AX.25), Pager (POCSAG), Radiosonde (RS41), Time signal (MSF, DCF77, TDF and WWVB) modems.
  • RTL SDR, Airspy, Airspy HF, LimeSDR, HackRF and SDRplay support via USB OTG as well as networked SDRs
  • 2D and 3D signal analysis in both time and frequency domain with statistical measurements of SNR, THD, THD+N, SINAD, SFDR and channel power
  • Satellite tracker, star tracker, maps and rotator controller

It should work on Android 6 and up. It’s a straight port of the desktop application, so although it will run on a phone, probably best used on a large tablet with a stylus or mouse.

SDRangel on Android
SDRangel on Android

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