Category: Amateur Radio

Next International Space Station SSTV Event on April 11 – 14

Thank you to Alex Happysat for writing in and letting us know about the next upcoming ISS SSTV event which will begin on 11 April at about 18:00 UTC and end on 14 April 2019 18:00 UTC. If you were unaware, the International Space Station (ISS) transmits SSTV images several times a year to commemorate special space related events. SSTV or Slow Scan Television is an amateur radio mode which is used to transmit small images over radio signals.

The images will be transmitted constantly at 145.8 MHz over the active period and they are expected to be in the PD-120 SSTV format. To receive the images you can use a simple RTL-SDR dongle and the MMSSTV software. A tuned satellite antenna like a QFH, turnstile, or tracking Yagi would be preferred, but many people have had good success before using simpler antennas like a V-Dipole. Software like Orbitron, GPredict, various Android apps or NASA's Spot the Station website can be used to determine where the ISS is and predict when it will be over your location.

Over on the ARISS SSTV blog, they write:

The next big event will be the ARISS SSTV event that starts Thursday, April 11 about 18:00 UTC and will be operational until about 18:00 UTC on Sunday, April 14. Since this event will run continuously for 72 hours, folks in the higher latitudes should have a pretty good chance to receive all 12 of the images. Operators in the mid latitudes should be able to get most of them depending on location. Good Luck and Enjoy!

Alex also mentions that for this and other ISS events AMSAT Argentina is handing out ARISS-SSTV Diplomas to amateur radio operators who receive, record and upload at least 15 images received from the ISS, in at least two different radio operation with a month or more in between then.

If you cannot set up a receiver, it is possible to use R4UAB's WebSDR which will be available directly at However, note that internet reception is not valid for the AMSAT Diploma. An example of WebSDR SSTV reception and decoding from a smaller ISS SSTV event held a few days ago is shown below.

ISS SSTV R4UAB WEBSDR 12.04.2016 14:00 UTC

Ghosts in the Air Glow HAARP Art Project: Transmitting Until March 28

The famous HAARP (High Frequency Active Auroral Research Program) antenna array will be transmitting again from March 25 - March 28, 2019. HAARP is an antenna array which is used to perform experiments on the Earth's ionosphere and thermosphere by transmitting HF RF energy into it. With an HF capable receiver like the RTL-SDR V3 it is often possible to receive these transmissions from some distance away. As HAARP only rarely transmits, it is an interesting signal to catch when it is transmitting.

HAARP (High Frequency Active Auroral Research Program)
HAARP (High Frequency Active Auroral Research Program)

The current set of experiments are being combined with an art project by artist Amanda Dawn Christie (@magnet_mountain). Amanda is an interdisciplinary artist working at Condordia University. On the project website she explains the project:

Ghosts in the Air Glow is an ionospheric transmission art project using the HAARP Ionospheric Research Instrument to play with the liminal boundaries of outer space.

Pairing air glow experiments in the ionosphere—false auroras creating soft, glowing spots in the sky—with SSTV images, audio and image signals articulated by artist Amanda Dawn Christie will be received and decoded via SDR (Software Defined Radio) equipment by amateur radio operators around the world, and streamed live online for audiences who do not have the equipment or expertise for reception.

She also talks about the project on a Concordia University article:

The first art transmission was sent earlier today, and if you missed it Amanda live streamed the signals being received on YouTube and the recording is available here. Future live streams will be available here. DK8OK has also posted about his reception on his blog.

Further transmissions are scheduled every day until March 28, and the transmissions schedule is available here. Each transmission consists of several 'movements', which consist of differing antenna array arrangements, frequencies being used, and signals being transmitted. If the text formatting of the movements is a bit difficult to read, Reddit user 
grink has formatted it into a nice table in his post. To follow the transmissions it would be also wise to follow Amanda on Twitter, where she is posting the most up to date transmission frequencies.

As to how the idea for this project came about, the Concordia University article writes:

The idea for the project came about when Christie met Christopher Fallen, the chief scientist at HAARP, at a hackers conference earlier this year. Fallen, who is an amateur radio operator, was intrigued by Christie’s proposition to use the IRI to create site-specific transmission art.

He agreed to open the facility to her, and when she gained backing from the Canada Council for the ArtsGhosts in the Air Glow officially became the first Canadian-funded project to take place at HAARP.

“Art and science are often seen as separate efforts but they actually share many of the same inspirations and techniques. I’m excited to see HAARP, a unique scientific instrument, used for a comparably unique artistic performance,” says Fallen.

“Amanda’s project will be a valuable contribution to the 50-year collection of scientific work in the field of ionosphere radio modification, and also to the brand new collection of artistic work using powerful high-frequency radio transmitters and the upper atmosphere — it’s art directed from the ground but created in space!”

Interdisciplinary artist Amanda Dawn Christie. Photo by Concordia University
Interdisciplinary artist Amanda Dawn Christie. Photo by Concordia University

If you prefer a video explanation of the project, YouTube user OfficialSWLchannel has prepared a video which is shown below.

HAARP tests and Ghost in the Air Glow from Amanda Dawn Christie

Building a Transmit/Receive Relay System for a “Boat Anchor” Transmitter and SDRplay

Over on YouTube user ElPaso TubeAmps has uploaded a video showing his transit/receiver relay system that allows a "boat anchor" (old radio) ham radio transmitter and SDRplay SDR receiver to coexist. In order to protect the SDRplay's front end from being destroyed by a ham radio transmitting on the same antenna, a relay should be used to ground the SDRplay during a ham radio transmission. He writes:

How to build a small chassis and relay system to switch the antenna from the SDR input to ground and open the speaker connection from the PC to the speakers during transmit. I use "boat anchor", i.e. separate VFO for transmitter and receiver equipment and this video is about that type of connection and is not for transceivers.

SDRPlay, RTL-SDR, Transmit-Receive , PC Speaker, T/R Switch

SignalsEverywhere: SDRAngel PlutoSDR Transmit Tutorial

Over on his YouTube channel SignalsEverywhere, Corrosive has uploaded a new video tutorial showing us how to transmit with a PlutoSDR and SDRAngel. His tutorial goes over the initial set up steps, selecting a modulator and changing modulator settings. He then goes on to demonstrate transmitting CW Morse code, using a CTCSS squelch tone and transmitting a Robot36 SSTV image via Virtual Audio Cable and MMSSTV.

SDRAngel Transmit Tutorial with PlutoSDR

Transferring Files via the BlockStream Satellite with Lightning Network Payments and RTL-SDR + Transacting Bitcoin over HF

The Blockstream satellite API is now live on the main Bitcoin network. Blockstream satellite is a project that aims to use geosynchronous satellites to strengthen the Bitcoin network by continuously broadcasting the Bitcoin blockchain all over the world. This allows people without internet access (or with censored internet) to receive Bitcoin. Setting up a Blockstream satellite receive station is a matter of building an RTL-SDR based receiver (or other GNU Radio compatible SDR) with a small satellite dish and LNB.

The API was also updated and this has enabled a feature that allows you to upload a file of up to 10 kB via the internet, which will then be transmitted via the satellites to anyone who is running a Blockstream RTL-SDR satellite receiver. Payment for the transmission is taken via the Bitcoin Lightning Network and transmissions appear to work on a priority basis, with larger payments receiving higher priority. The file is distributed to all receivers, so they note that private messages would need to be encrypted with public keys distributed to recipients in other ways. This service is similar to what the Othernet (prev. Outernet) network offered in the past with the ability to transmit data, tweets and APRS messages over their satellite network. We think that cheap small data satellite transmissions could have some interesting applications in remote control.

In related news on CryptoNewsZ it has been reported that a bitcoin lightning network transaction was completed over the 20M amateur radio band. The transaction was completed with the JS8 digital mode, which is similar to FT8 but designed for weak signal usage. The message was sent via the help of twitter, with @eiaine first sending money to @nvk via the internet. @nvk then sent the Lightning Network invoice over 21 JS8 messages via the 20M band to @eiaine who received it, thus confirming that the transaction was completed.

DIY Software Defined Ham Transceiver With eBay Parts

YouTuber jmhrvy1947, has recently uploaded a number of videos giving an overview of how he built his own HF SDR transceiver using what he calls the “Lego build method”. The idea of the Lego build method was to build a transceiver with parts picked and pulled from eBay so that it could be easily reproduced by others. There are a few scratch made components however those designs are available on his GitHub page. The SDR only functions within about 100 kHz of spectrum at a time however for amateur radio HF work this is more than sufficient. Bare bones the radio puts out a mere 100 mW and although the output power is small, he’s made contacts up to 450 miles away using CW (Morse code). You also have the option of adding an amplifier on  your output if you are looking for more power than that. His final revision currently puts out 100 Watts.

Using modified versions of fldigi and Quisk he is able to easily work various digital modes and sync the transmitter and receiver together. The only real down side to this radio is that you must switch out your receive and transmit filters whenever you wish to operate on different bands, a process that really only takes a moment or two.

Check out his videos on the project – it’s really amazing to see what can be done with a small budget these days in radio and with how far software defined concepts have brought us.

DIY SDR CW Xcvr Project

In the video below you’ll see an explanation of the software involved in this build.

DIY SDR CW Software


Using Two PlutoSDR’s for Full Duplex Packet Radio Communications

Over on his channel SignalsEverywhere, Corrosive has uploaded a video showing us how we can create a full duplex packet radio communications system using two PlutoSDRs. Full duplex is the ability to transmit and receive at the same time. A single PlutoSDR is only half-duplex/simplex because it can only either receive or transmit at any one time. The PlutoSDR is a low cost (typically $99 - $149) RX/TX capable SDR with up to 56 MHz of bandwidth and 70 MHz to 6 GHz frequency range. 

On his video Corrosive explains how full duplex operation is desirable for amateur packet radio communications as it allows for faster and more continuous exchanges.  Demonstrations are performed with his PlutoSDR, SoundModem, EasyTerm, and SDRAngel. Later in the video he also speculates how it might be possible to do things like IP networks via the amateur radio bands with full duplex SDRs.

Full Duplex Radio Communication with PlutoSDR Tutorial

Reducing HF Electrical Noise by Using a Faraday Cage for Switch-Mode Power Supplies

Over on his blog, DXer OH2-2192 was frustrated by lots of local electrical noise showing up on the HF bands on his Airspy + Spyverter SDR receiver. He discovered that the majority of the noise he was seeing was coming from the switch mode power supplies that power the electronic devices used in his setup. Switch mode power supplies are very common in the modern world, with almost every electronic device using one to efficiently convert wall AC into DC power. However, they convert power by rapidly switching on and off, and these on/off square wave pulses cause a lot of RF noise especially on the HF spectrum.

Instead of changing to noise free linear regulators which are expensive, very heavy and big, OH2-2192 decided that he'd try creating a Faraday cage shield out of metal mesh to enclose all his switch-mode power supplies. Using a simple AM loop antenna and Airspy's Spectrum Spy software he measured the amount of noise produced by a switch-mode supply placed inside and outside of the cage. The results he saw were very promising with the shielded supply eliminating the noise almost entirely.

Faraday Cage Shield for Switch Mode Power Supplies
Faraday Cage Shield for Switch Mode Power Supplies (Right image shows the results of a switching supply placed outside and inside the Faraday cage)