Category: Applications

Standalone Windows FengYun-3 & MetOp HRPT Weather Satellite Decoder

Back in June we posted about Alan (@aang254)'s work on porting the GNU Radio gr-hrpt decoder over to GNU Radio 3.8. More recently Alan wrote in and wanted to share the news that he has recently released standalone Windows decoders for the MetOp and FengYun-3 weather satellites.

MetOp and FengYun-3 are both polar orbiting satellites that beam back high resolution weather satellite images. Unlike the NOAA polar orbiting satellites which transmit both the easy to receive APT and more advanced HRPT signal, these only transmit a HRPT signal at ~1.70 GHz, so a satellite dish and motorized tracking mount (or hand tracked) is required. You will also need an SDR capable of receiving over 3 MHz bandwidth such as an Airspy Mini or R2. Alan writes:

I recently got FengYun decoding working after the release of my MetOp decoder a while ago. Since gr-hrpt wasn't usable for Windows user without some major hassle, I made some standalone decoders (Windows builds included in the repo) for both MetOp and FengYun.

Decoding is done by first demodulating with the included flowcharts or @petermeteor's, then processed through the decoder which does Viterbi / Differential decoding. The output then needs to be deframed by MetFy3x or any other software that can do so.

https://github.com/altillimity/Satellite-Decoders

A few images!

https://twitter.com/SamuelArmstro18/status/1285647473881513989
https://twitter.com/ZSztanga/status/1285277472284708865
https://www.reddit.com/r/amateursatellites/comments/hwhb7q/my_longest_fy3b_image_yet_i_got_up_at_430_in_the/
https://twitter.com/HA6NAB_Tomi/status/1285300023350222848
https://twitter.com/ub1qbj/status/1286734822820532224/photo/1

You can learn more about these satellites on USA-Satcom's Cyberspectrum talk and slides.

SignalsEverywhere: SDRTrunk P25 Police Scanner Tutorial with two RTL-SDRs

Over on YouTube Sarah from SignalsEverywhere has uploaded a new tutorial video showing how to use two RTL-SDR dongles with the free SDRTrunk software to create a P25 Police scanner.

In the video she first shows how to install SDRTrunk in Windows and Linux, then how to install the JMBE codec required for decoding audio. She goes on to show how to import trunked system network data from a (paid) RadioReference subscription, how to blacklist unwanted talkgroups, and how to optimize operation with two RTL-SDR tuners. Finally she also shows how to set up the system manually if you don't have a RadioReference subscription.

SDRTrunk The FREE P25 Police Scanner! Windows and Linux Tutorial

Alpha Version of SDR++ Released

SDR++ is an open source general purpose cross platform SDR program that Alexandre Rouma (@WhatsTheGeekYT) has been working on for the past few months. Recently he released his first Windows Alpha version to the public which is available from the GitHub release page. The SDR++ GUI is inspired by SDR#, however, SDR++ as you might guess is programmed in C++ instead of C#.

In order to use SDR++ on Windows you will first need to have installed PothosSDR for the SoapySDR and volk support. To do this you can follow the instructions here. Thanks to the SoapySDR support it is able to run with most SDRs including the RTL-SDR.

To start the program, select your SDR from the source menu, change the sample rate (which is set to the minimum value by default), then click the play button. We tested it with both an RTL-SDR and HackRF, and both units worked just fine, although at lower sample rates the waterfall was a bit choppy. We do note that the software is very much in the alpha phase with only a few features implemented, and most menu items do not work yet. But the main features including WFM, FM, AM, SSB, CW demodulation as well as the spectrum and waterfall are all functional. Unfortunately there do seem to be a few stability issues as we experienced frequent crashes on our PC.

We'll be watching this software with interest to see how it progresses.

Current Features

  • Uses SoapySDR for wide hardware support
  • Hardware accelerated graphics (OpenGL + ImGui)
  • SIMD accelerated DSP (parts of the DSP are still missing)
  • Cross-platform
  • Full waterfall update when possible. Makes browsing signals easier and more pleasant

Coming soon

  • Multi-VFO
  • Plugins
  • Digital demodulators and decoders
  • Quick replay (replay last n seconds, cool if you missed a short signal)

Small things to add

  • Switchable bandwidth for demodulators
  • Switchable audio output device and sample rate
  • Recording
  • Light theme (I know you weirdos exist lol)
  • Waterfall color scheme editor
  • Switchable fft size
  • Bias-T enable/disable
  • other small customisation options
  • Save waterfall and demod settings between sessions
  • "Hide sidebar" option
  • Input filter bandwidth option

Known issues (please check before reporting)

  • Random crashes (yikes)
  • Gains aren't stepped
  • The default gains might contain a bogus value before being adjusted
  • Clicks in the audio
  • In some cases, it takes a long time to select a device (RTL-SDR in particular)
  • Min and Max buttons can get unachievable values (eg. min > max or min = max);
The SDR++ Interface
The SDR++ Interface

Frugal Radio: Using an Airspy and RTL-SDR To Scan the UHF Military Airband in SDR#

In Frugal Radio's latest video he explores how you can use an Airspy or RTL-SDR dongle to scan the entire military UHF airband spectrum in a few seconds via SDR#. Frugal Radio notes that there are often many signals in the UHF milair band, but they can be difficult to find without a scanner.

In the first video he compares his Uniden BCT15X hardware radio scanner against an Airpsy, noting that his Uniden takes 1:10 minutes to scan the entire band, whereas the Airspy running SDR# with the frequency scanner community plugin can scan the same bandwidth in less than 2.5 seconds. Faster scanning means that you are less likely to miss an active signal. In the second video he tries scanning with an RTL-SDR and notes that it can scan the band in 9 seconds.

How to use Frequency Scanner to Search UHF MilAir in 2.3 seconds in SDR# using AirSpy R2

$25 RTL-SDR v3 Military Air band search in under 10 seconds! Frequency Scanner SDR Sharp plugin test

Using CubicSDR, rtl_433, MQTT and Telegraf to Stream Live Data to InfluxDB

Nimrod makes his own sourdough and wanted a way to track the temperature and humidity of the bread making environment. To do this he's set up a system involving rtl_433 on a Raspberry Pi which live streams all of his home temperature/humidity sensor data into InfluxDB. The program rtl_433 is software for the RTL-SDR that allows users to receive data from many different brands of home weather/temperature sensors, as well as many other wireless ISM band devices. InfluxDB is a type of database that specializes in storing and displaying time series data from sources like sensors.

The chain of data starts with rtl_433 which collects the temperature sensor data via an RTL-SDR. The output of rtl_433 is sent to Mosquitto, an MQTT messaging protocol server. A program called Telegraf then subscribes to the MQTT queue, and parses and transmits the metrics to InfluxDB. InfluxDB finally records the data, and provides graphical plots. 

Nimrod's post is a full tutorial showing how to download and set up each of the programs used in the system, and how to view the data collected with InfluxDBs graphing system.

RTL_433 temperature graphs via InfluxDB
RTL_433 temperature graphs via InfluxDB

Frugal Radio: 2020 SDR Guide Ep 2 – Using Free Online SDRs

Over on his YouTube channel Frugal Radio has released the second episode in his 2020 SDR Guide series. In this video, Frugal Radio shows how to connect to remote SDRs such as KiwiSDR OpenWebRX, WebSDR, SDR-Console v3 Servers, and SDR# SpyServers. He shows how to use these remote SDRs to monitor long range aviation channels, amateur radio operators, and VHF Public Safety channels in the US. He also demonstrates how to decode HFDL signals from aircraft using WebSDR and free software, and verifies the aircraft locations via online tracking sites.

2020 SDR Guide Ep 2 : How to use over 500 remote SDRs free online (webSDR, KiwiSDR & HFDL decode)

Tracking Wild Bats with SDRs – Featured in Science Magazine

Recently research from Tel-Aviv University by Sivan Toledo et al. involving the use of USRP SDRs to track wild bats was published in Science.  The Journal Science (aka Science Magazine) is one of the world's top peer reviewed academic journals.

Sivan and his collaborators developed inexpensive 434 MHz band tracking tags for bats that emit radio pings every few seconds. These pings do not contain any location data, however the location is accurately tracked by several USRP SDRs with high accuracy GPSDO oscillators set up around the target tracking area. A radio direction finding technique known as "time difference of arrival" or TDoA is used to pinpoint the location of each tag. Sivan writes:

A wildlife tracking system called ATLAS, developed by Sivan Toledo from Tel-Aviv University in collaboration with Ran Nathan from the Hebrew university, enabled a science breakthrough reported in an article in Science that was published yesterday.

The system uses miniature tracking tags that transmit radio pings in the 434 MHz bands and SDR receivers (Ettus USRP N200 or B200). Software processes the samples from receivers to detect the pings and to estimate their time of arrival. The overall system is a "reverse-GPS" system, in the sense that the principles and math are similar to GPS, but the role of transmitters and receivers is reversed. A youtube video explains how the system works. SDR-RTL dongles can certainly detect the pings, but their oscillators are not stable enough to accurately localize the tags.

The system has been used to track 172 wild bats (in batches, some consisting of 60 simultaneously-tagged bats). The results showed that bats can make novel shortcuts, which indicates that they navigate using a cognitive map, like humans. The system, and other ATLAS systems in the Netherlands, England, Germany, and Israel are also tracking many different animals, mostly small birds and bats.

The video below shows the bats being tracked on a map accelerated to 100x.

434 MHz Tracking Devices that Attach to Wild Bats
434 MHz Tracking Devices that Attach to Wild Bats

The Science article itself is mostly about the discoveries on bat behaviour that were made by the system. However the YouTube video embedded below explains a bit more about how the technical radio side works. 

A Technical Overview of the ATLAS Wildlife Tracking System

Controlling Frequency in SDR# with a Barcode Scanner

Thank you to Manuel Lausmann for submitting his YouTube video showing how he has set up a system that allows him to rapidly change frequencies in SDR# with a barcode scanner and some barcodes printed via an online generated. This might be an interesting way for non-technical users to easily change frequencies on demand, for example in a public demonstration of various radio channels.

We note that the video is narrated in German, but you can use the YouTube auto-translation feature to get English subtitles.

Schneller Frequenzwechsel mit einem Barcode Scanner