Gerrit's weather station wirelessly displays data on a wirelessly connected LCD screen, but he notes how difficult it is to view historical data, or to graph trends. Having discovered that the rtl_433 RTL-SDR decoder supports his particular weather station (a Fine Offset Electronics WH1080/WH3080 compatible Weather Station (Alecto WS-4000)), Gerrit decided to write some code to log data to a SQL database, and display that data via a Python Dash.plotly web interface. The RTL-SDR, rtl_433 and custom software all run on a Raspberry Pi.
The interface allows Gerrit to view live and historical data all on neatly plotted graphs. HIs complete open source code can be found on Github.
Dash.pltly based weatherstation with data received by RTL-SDR and rtl_433
Thank you to Ryan K for submitting his latest blog post where he gives an in depth explanation of how he reverse engineered his La Crosse weather station using an RTL-SDR, PlutoSDR and the Universal Radio Hacker (URH) software.
The La Crosse weather station system consists of a LCD base station, and various wireless sensors. Ryan first discovered that the devices used the 915 MHz frequency band via details written on the device itself. His next step was to open up Universal Radio Hacker and use one of his SDRs to record a packet. URH then allowed him to convert that data into bits for packet analysis. The rest of his post goes into detail on how he set the symbol rate, discovered the preamble and reverse engineered the CRC code.
The next step he took was to generate a spoofed packet generated by URH and transmitted by the PlutoSDR. This allowed him to set the base station display to any temperature that he specified. But he ran into a problem where only the first packet he sent after power up was received. Eventually he discovered that the system sets a randomized interval for each of the transmitters at startup, and data outside of that interval is ignored.
Ryan's post explains his whole though process and progress in detail, so is an excellent study for anyone looking to get into reverse engineering wireless signals.
Reverse Engineering a La Crosse Weather Station with a PlutoSDR and RTL-SDR
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.
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.
Black Cat Systems have recently released two new programs that may be of interest to HF monitoring enthusiasts. The first is a multichannel capable ALE decoder and the second is a multichannel GMDSS-DSC decoder. Both programs are not free, with an (introductory) price tag of $29.99 each for three parallel input channels, and $99 for up to 24 parallel input channels.
With an appropriate HF capable SDR, like a SDRplay, Airspy HF+ Discovery, or even an RTL-SDR V3 in direct sampling mode, these programs allow you to set up a home monitoring station.
ALE or Automatic Link Establishment is a digital RF protocol that enables users to initiate a reliable call over HF frequencies, by automatically choosing the best frequency based on propagation conditions, allowing for telephone like calling operation, and enabling short text messages.
GMDSS or Global Maritime Distress and Safety System is a set of radio protocols that enables digital text communications between ship to ship and the shore, as well as weather broadcasts, and distress beacons.
Over on his blog Nils Schiffhauer (DK8OK) has been testing these two programs out. In his first post about the ALE decoder, Nils explains ALE in more depth, and demonstrates how he uses the multi-channel capable SDR-Console with Virtual Audio Cable to feed 16 ALE channels into the decoder. He goes on to show how to filter by callsign and provides some tips for best reception. He notes that with ALE you might receive messages from:
... forces, diplomatic services, emergency agencies, police, militia, UN missions, drug enforcement, border control and even amateur radio. It is used from aircraft like AWACS, as from aircraft carriers, from mobile units to fixed stations.
In his second post Nils tests out the GMDSS decoder noting that it is an "extraordinary sensitive decoder" and "it also includes smart processing of the data – from looking up vessel’s complete data from ITU’s Ship Station List (internet connection needed) to saving all data to a fully-fledged database". His post goes on to explain the GMDSS format in more detail and demonstrate multichannel decoding.
Black Cat Systems ALE and GMDSS Decoders demonstrated by Nils Schiffhauer (DK8OK)
Derek OK9SGC has recently posted a write-up of how they’ve been able to receive the Ku-band beacon signals from the Starlink constellation of communication satellites continually launched by SpaceX since 2015. While we recently covered Starlink Beacons being captured with a HackRF Supercluster Derek has noted that receiving the beacons requires little more than an LNB, a low-cost SDR such as the RTL-SDR V3 and a power injector to provide 12V DC to the LNB. Derek notes that a dish is not even required as the beacons transmit with high power.
Starlink Beacon Receiver Setup
Due to the low earth orbit and thus high speed of travel of the Starlink constellation you’ll notice strong Doppler effect drifts in your received signal. Derek notes that it may be interesting to perform Doppler analysis on the satellites with the satellite tracking toolkit for radio observations (strf) software. He also noted that in the 30 minutes he was receiving for, there was almost no point in time where a beacon was not being received, indicating that the Starlink constellation is close to achieving 100% sky coverage.
Derek has made the process easy to understand and illustrates just how easy it is to listen to these beacon signals. Of course we note that these are just the beacons, and they carry no data. Still they are fun signal to receive, and doppler analysis could reveal interesting information about orbits.
Starlink beacons shown in a fast FFT (LEFT), and slow FFT (RIGHT)
In this weeks Frugal Radio episode Rob explores some low cost "Step Up" radios that for a moderately higher price, can give improved receiver performance when compared to RTL-SDRs .
In the video Rob overviews and compares the Airspy Mini ($99), SDRplay RSP1A ($119), Airspy R2 ($169) and the Airspy HF+ Discovery ($169). He discusses their differences such as the tuning ranges, bandwidths and ADC bit depths and why these parameters matter.
Over on Reddit u/Xerbot has posted about the release of his new software called "LeanHRPT". When combined with a software defined radio, this software can be used to decode and view HRPT weather satellite images received from satellites such as NOAA, Meteor, MetOp and FengYun. We note that unlike APT and LRPT weather satellite signals which transmit in the VHF bands, HRPT signals are generally at ~1.70 GHz and require a motorized or hand tracked satellite dish to receive. u/Xerbot writes:
LeanHRPT is a flexible, easy to use and powerful set of tools for the manipulation of HRPT data (maybe I could be convinced to add LRPT support).
When used properly LeanHRPT Decode can generate (almost) L1B data usable in actual land/weather observation, or just pretty images :)
The LeanHRPT project also contains LeanHRPT Demod, as you probably guessed, a HRPT demodulator. It features an incredibly high sensitivity as well as being able to do both realtime (through SoapySDR) and offline demodulation (baseband).
The GNU Radio conference talks are generally about cutting edge SDR research topics and the YouTube playlist contains 67 videos covering a gambit between what changes have been made in new releases of GNU Radio to presentations and demonstrations focusing on topics such as reverse engineering smart power meters and 5G cell detection among many others.
Some of the talks from this years conference that we found most interesting include:
