Tagged: amateur radio

GridTracker: A WSJT-X Mapping Program

Thanks to RTL-SDR.com reader Henry for letting us know about the release of a new piece of Windows software by Tag Loomis (N0TTL) called GridTracker. GridTracker is a live mapping program for WSJT-X which is a software decoder for low power weak signal ham communications modes such as FT8, JT4, JT9, JT65, QRA64, ISCAT, MSK144 and WSPR. Although these are low power modes, the protocols are designed such that even weak signals can potentially be received from across the world. Mapping the received signals can be interesting as it may give you an idea of current HF propagation conditions.

GridTracker is a Windows (XP or above) companion program for WSJT-X. It listens to WSJT-X or JTDX decodes and displays them on a map.

A great way to visualize communicating amateurs around the world!

Display on a large second monitor in your amateur radio club, hamfest or as a demonstration in a classroom. Everyone gets excited when they can see what you’re doing!

You can also load your ADIF log files from WSJT-X, Qrz.com, LoTW, PSKReporter and others to get a visual view of ‘stations worked’, stations that can hear you and more!

It might be an interesting project to set up a permanent GridTracker display using an RTL-SDR V3 in direct sampling mode, or RTL-SDR with upconverter. Low cost x86 single board PCs that can run Windows 10 such as the LattePanda, UP board or Udoo might be possible candidates for host hardware.

Henry warns us that the software is still new, so it may be a little buggy.

GridTracker Mapping out Weak Signal Communications.
GridTracker Mapping out Weak Signal Communications.

Using a Raspberry Pi 3 and RTL-SDR as a 40m FT8/JT65/JT9 Monitor

Over on YouTube user radio innovation has uploaded a brief screen capture showing his Raspberry Pi 3 and RTL-SDR dongle being used as an always-on monitor for low transmit power based signals such as FT8, JT65 and JT9. These signals are transmitted by ham radio enthusiasts for the purpose of making contacts, and determining propagation conditions. This is a good application for an RTL-SDR and Raspberry Pi 3 as it enables cheap monitoring of these signals without the need to tie up a full sized ham radio.

To do this "radio innovation" runs Linrad on the Raspberry Pi, which is a program like GQRX that interfaces with the RTL-SDR dongle. Then the WSJTx software is used to decode the signals. He writes:

Remote Desktop screencapture of my Raspberry Pi3 monitor receiver on 40m amateurradio band with WSJTx and decoding FT8,JT65 and JT9. Receiver hardware is RTL-SDR(tcxo) + simple converter and homemade bandpass filter.

SDR software is LINRAD by SM5BSZ.

RasperryPi3 OS is Ubuntu Mate 16.04.

YouTube Talk by Ria Jairam: SDR & Setting Up A World Class Station

Over on YouTube FairlawnARC.org have uploaded a talk about SDRs and ham radio by Ria Jairam (N2RJ0). The talk is a good overview of the current state of SDRs for ham radio use, and she discusses the various hardware and software options as well as giving many tips for improving your ham station. The blurb reads:

Our speaker was Ria Jairam (N2RJ), a world class contest operator and member of the Frankford Radio Club. Ria discussed the latest technology and offerings from Flex Radio, the HPSDR project (Ananradios), RTL SDR and others, as well as practical tips for contesting, DXing and rag chewing using your SDR. This presentation was held on Friday, October 20, 2017, 1900 hours at the Fair Lawn Senior Center, 11-05 Gardiner Road, Fair Lawn, NJ. The event was open to the public & refreshments were served.

CyberSpectrum Melbourne: Building a Cheap FSQ Transceiver with Arduino, Raspberry Pi and RTL-SDR

FSQ (Fast Simple QSO) is a relatively new ham band mode for making text QSO’s (contact or exchange of information with another ham) over HF frequencies. It is a low data rate mode similar to PSK31 but with some interesting features like relaying which allows signals to be relayed further via other FSQ stations.

Over at in Melbourne, Australia a Cyberspectrum SDR meetup is held every few weeks. At this weeks meetup @faulteh discusses the FSQ mode and some of it’s interesting features. He also shows how he can transmit FSQ using a Si5351 clock generator and Arduino (with filtering). In the future he hopes to also create a fully automated receive station using a Raspberry Pi and RTL-SDR dongle.

The Arduino FSQ code is available on GitHub, and more information is available on his hackaday.io page.

A Tour of Satellites in the QB50 Experiment

Over the last two weeks the QB50 experiment was launched from the International Space Station (ISS). The experiment consists of 36 cubesats built by various universities around the world, with the main science goal being to make measurements of the thermosphere (an upper atmospheric layer that the ISS orbits in). All the cubesats broadcast their telemetry in the 70cm (420 – 450 MHz) amateur band and they are expected to stay in orbit for about 3 months before falling back to earth. In a previous post we made a point to mention Lilacsat-1, which is one of the most interesting QB50 satellites due to its implementation of a FM to digital voice repeater on board.

The QB50 Experiment Launch
The QB50 Experiment Launch

Over on his blog destevez has been following these satellites, and has uploaded a post that shows him receiving and decoding several of the satellite telemetry packets. His gr-satellites GNU Radio package provides a means to decode many of the satellites in the experiment.

Some packets from QB50 and other satellites in the 70cm amateur band.
Some packets from QB50 and other satellites received by destevez in the 70cm amateur band.

Decoding the LilacSat-1 FM to Digital Voice Transponder

LilacSat-1 is an educational CubeSat built by students from the Harbin Institute of Technology (HIT) in China. It was recently launched from the ISS on 25 May 2017 as part of the QB50 science experiment to explore the lower thermosphere, and it is expected to stay in orbit for about 3 months. Apart from BPSK telemetry at 145.935 MHz, LilacSat-1 is interesting because it contains on board an FM to Codec2-BPSK digital voice amateur radio transponder at 145/436 MHz (uplink/downlink). It is probably the first amateur radio satellite to contain an FM to digital voice transponder.

To decode LilacSat-1 digital voice and telemetry you can use a Linux live CD provided by HIT, or download the GNU Radio decoder directly from the LilacSat-1 information page on the HIT website. The GNU Radio program can be used with any GNU Radio compatible SDR, such as an RTL-SDR.

Over on his blog, destevez has also created a lower latency digital voice decoder for LilacSat-1 that can found in the gr-satellites GNU Radio package, which contains decoders for multiple satellites as well. Destevez has also written about the Codec2 implementation used in LilacSat-1 in one of his previous posts.

An example of LilacSat-1 being decoded has also been uploaded by YouTube by Scott Chapman. In his test he used an RTL-SDR to work the pass live, but in the video shows an offline decoding received by his SDRplay which was also monitoring the same pass.

DK8OK Review of the Airspy and SpyVerter

Recently DK8OK wrote in to us and wanted to share his latest review of the Airspy and SpyVerter combo (pdf). His review focuses on HF usage and he shows various examples of HF signals that he has received with the Airspy+SV such as the CHU time station, STANAG, DRM, ALE, HFFAX, VOLMET and HFDL. He also shows some tricks for optimizing HF reception, a tutorial on performing multi-channel audio recording and decoding in SDR-Console, a tutorial on playing and analyzing recorded files as well as some examples of weak signal reception.

Overall DK8OK praises the Airspy+SV combo citing it’s excellent dynamic range as one of the reasons it performs so well.

We should note that for prospective buyers, the Airspy team is currently working on a new complimentary solution for HF monitoring called the Airspy HF+. This will have extremely high dynamic range (even higher than the Airspy+SV combo), but it will have a smaller bandwidth. So the Airspy+SV combo will still be the best for monitoring a wide 9 MHz chunk of the HF band, whilst the HF+ will be the best for getting into those very hard to receive signals.

Update: The paper is now also available in French.

Multi-channel decoding in SDR-Console with the Airspy+SypVerter
Multi-channel decoding in SDR-Console with the Airspy+SpyVerter

A Pre-Built Raspberry Pi Image for using an RTL-SDR as an APRS RX iGate

Keith Maton (G6NHU) wrote in and wanted to share his new ready to go APRS RX iGate image for the Raspberry Pi. APRS stands for “Amateur Packet Reporting System”, and is a type of packet radio communications system used by Amateur Radio operators. They often use them to transmit short mail messages, weather sensor updates, track vehicles and for various other purposes. An iGate allows APRS messages to be transmitted over the all world via the internet via a signal chain such as: RF->iGate RX->Internet->iGate TX->RF.  To run an iGate you should be a radio amateur with a callsign. A global aggregation of APRS broadcasts received by iGates can be seen at aprs.fi.

An RTL-SDR can be used to receive APRS packets easily and many amateur radio enthusiasts have been setting up APRS RX only iGates using the “direwolf” decoding software. Keith’s image simplifies the process of installing and configuring software significantly by proving a plug and play image that you just burn to an SDcard and plug into your Raspberry Pi. His post also explains how to configure the iGate correctly.

iGate Raspberry Pi Image Running
iGate Raspberry Pi Image Running