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.
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.
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.
In the latest video on the Signals Everywhere YouTube channel, Sarah investigates how a PlutoSDR can be used as a Spectrum Analyzer with the SATSAGEN software. The SATSAGEN software is able to work as a spectrum analyzer by rapidly sweeping over multiple frequencies and stitching the spectrum slices together. It support SDRs like the HackRF, PlutoSDR and RTL-SDR (in receive mode only). The PlutoSDR can transmit, so it is able to work as a full spectrum analyzer with tracking generator, allowing users to measure RF devices such as filters, tune antennas, and work as a frequency generator.
In the video Sarah demonstrates how to use the PlutoSDR and SATSAGEN to measure our RTL-SDR Blog Broadcast FM filter, and to tune our multipurpose dipole antenna.
Spectrum Analyzer and Tracking Generator with Pluto SDR
Thank you to everyone who has backed or been following our KrakenSDR project on Crowd Supply. The initial funding campaign has now concluded with almost 5x our minimum funding goal! If you missed out, please don't worry as the product is will still be available for sale on Crowd Supply at the campaign price, but later orders may receive units from the second batch produced a few months after the first.
Thanks to the successful funding campaign we now have all the required parts on order and we expect the factory to receive them in a few weeks time. The final confirmation prototype is in production now, finishing touches to the enclosure are being worked on, a QC process is being developed and EU compliance certification and logistics details are being worked through.
At the same time work on on the DFing software is continuing to progress as well. If you are testing the software with the older KerberosSDR units, please note that the software is still in beta and that a thorough reading of the documentation is required to understand the DAQ control parameters. As direction finding with an SDR can involve learning a lot of new technical information, we are aiming to significantly simply the knowledge that is needed to understand the DAQ parameters, and hope to have a simplified version released with a tutorial by mid-December. So if you have a Kerberos, and are struggling with the setup, please kindly wait until the official release, unless you are interested in learning the nitty gritty technical details.
Recently we have also been working on improvements to the intermittent signal squelch handling and we are also working on multichannel DFing capabilities. We have a new developer starting work on a multiplatform networked mapping program too.
We are also looking to sponsor some accelerator projects such an GNU Radio integration and beam forming investigations for applications like radio astronomy. If you have DSP programming skills, and you're interested in helping on this, or have the DSP skills and interest in developing another project, please email us at [email protected] with details.
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).
Back in July we posted about the release of Viol Tailor's "uSDR" software, which is a lightweight general purpose multimode program for Windows which supports the RTL-SDR, Airspy, BladeRF, HackRF and LimeSDR radios. Recently Viol has updated the software to V1.4.0. The new release brings SDRplay support, and various performance and GUI improvements listed below.
This week on the Tech Minds YouTube channel Matthew introduces the "Cloudmarkers" plugin for SDRuno. SDRuno is the official software for the SDRplay RSP line of software defined radios, but the EXTio version also supports the RTL-SDR.
Cloudmarkers is a plugin that allows users to query the online Cloudmarkers database to determine what an unknown signal at the currently tuned frequency might be. The database is created by other Cloudmarkers users, so if you have your own information to add you can add information about particular frequencies to the database for others to query later.
In the video Matthew shows the Cloudmarkers plugin in operation and notes that the plugin can work with both SDRplay SDRs and the RTL-SDR.