In a recent YouTube video Tech Minds shows how to decode GMDSS (Global Maritime Distress and Safety System) messages which are broadcast on MW and HF. In the video he explains the DSC (Digital Selective Calling) which allows calls to be made to individual ships, a group or all stations. He goes on to demonstrate the YADD GMDSS DSC decoder running via the HF audio piped in from SDRUno and received with an SDRPlay RSPdx.
Earlier in the month SDRplay released SDRuno V1.4 RC1. This is a beta version that amongst other changes now has the capability to run "plugins". Plugins allow developers to easily create modules that extend the functionality of the SDRUno software. For example right now there is a plugin included with V1.4 RC1 that allows users to listen to DAB audio. Up until recently plugin functionality has only been available in Airspy's SDR# software, so it's good to see SDRuno finally including this feature too.
Over on the Techminds YouTube channel Matthew has uploaded a short video where he tests out the new plugins feature. First he tests out the DAB decoder, noting that the CoreAAC codec needs to be installed first separately. Later he tests the second plugin which is an audio recorder that allows users to record audio to MP3.
Over on YouTube user Tech Minds has uploaded a video showing how you can determine if you are getting HF interference from a VDSL internet connection going to your house or neighbors. VDSL or Very High Speed Digital Subscriber Line is an internet connection technology that runs over old copper phone wires allowing for a fast broadband connection. The frequencies used by VDSL are between 25 kHz to 12 MHz, and for VDSL2 up to 30 MHz. Unfortunately the frequencies used can result in high amounts of radio interference from RFI radiating from the copper phone lines which is a major problem for HF amateurs and short wave listeners.
In his video Tech Minds uses an SDRplay RSPdx to record a short IQ file of the VDSL interference that he experiences in his home in the UK. He then opens the IQ file in a piece of software called Lelantos, which was developed by a member of the UK amateur radio organization RSGB. If a VDSL signal is present, this tool will determine various bits of information about the interference, and will give you enough information to make a complaint to OFCOM, the UK's radio communications regulator.
Over on YouTube TechMinds has uploaded a video where he explores the QT-DAB software (formerly known as SDR-J), which is a program capable of decoding Digital Audio Broadcast (DAB) signals. QT-DAB is compatible with several SDRs including the RTL-SDR, HackRF, Airspy and SDRplay units.
DAB stands for Digital Audio Broadcast and is a digital broadcast radio signal that is available in many countries outside of the USA. The digital signal encodes several radio stations, and it is considered a modern alternative or future replacement for standard analog broadcast FM.
In the video TechMinds explains how to download, install and use the software on a Windows machine. He goes on to demonstrate some DAB decoding in action with various SDRs and then shows how to connect QT-DAB to a remote RTL-SDR via rtl_tcp.
Over on the SWLing (Short Wave Listening) Post blog Thomas has just uploaded his review of the YouLoop in a post titled "The Airspy Youloop is a freaking brilliant passive loop antenna". If you weren't aware, we are currently selling this loop in our store for US$34.95 incl. free worldwide shipping to most countries. Sales are currently in pre-order as our first batch of units ordered sold out within a day, but we're soon going to receive the second batch in the next few days.
Thomas is a seasoned shortwave listener who has used many antennas, and in the review he notes that he is extremely impressed with the performance. In his review he tests the antenna in a location that is swimming with RFI and places the loop in the middle of a bedroom. Although the situation is not ideal, Thomas was surprised at the number of signals he was able to receive.
To work properly the YouLoop requires a low noise figure radio like the recommended Airspy HF+ discovery, but Thomas notes that he's also had excellent success with the SDRplay RSPdx running in HDR mode.
Librespace, who are the people behind the open hardware/source SatNOGS satellite ground station project have recently released a comprehensive paper (pdf) that compares multiple software defined radios available on the market in a realistic laboratory based signal environment. The testing was performed by Alexandru Csete (@csete) who is the programmer behind GQRX and Gpredict and Sheila Christiansen (@astro_sheila) who is a Space Systems Engineer at Alexandru's company AC Satcom. Their goal was to evaluate multiple SDRs for use in SatNOGS ground stations and other satellite receiving applications.
The SDRs tested include the RTL-SDR Blog V3, Airspy Mini, SDRplay RSPduo, LimeSDR Mini, BladeRF 2.0 Micro, Ettus USRP B210 and the PlutoSDR. In their tests they measure the noise figure, dynamic range, RX/TX spectral purity, TX power output and transmitter modulation error ratio of each SDR in various satellite bands from VHF to C-band.
The paper is an excellent read, however the results are summarized below. In terms of noise figure, the SDRplay RSPduo with it's built in LNA performed the best, with all other SDRs apart from the LimeSDR being similar. The LimeSDR had the worst noise figure by a large margin.
In terms of dynamic range, the graphs below show the maximum input power of a blocking signal that the receivers can tolerate vs. different noise figures at 437 MHz. They write that this gives a good indication of which devices have the highest dynamic range at any given noise figure. The results show that when the blocking signal is at the smallest 5 kHz spacing the RSPduo has poorest dynamic range by a significant margin, but improves significantly at the 100 kHz and 1 MHz spacings. The other SDRs all varied in performance between the different blocking signal separation spacings.
Overall the PlutoSDR seems to perform quite well, with the LimeSDR performing rather poorly in most tests among other problems like the NF being sensitive to touching the enclosure, and the matching network suspected as being broken on both their test units. The owner of Airspy noted that performance may look poor in these tests as the testers used non-optimized Linux drivers, instead of the optimized Windows drivers and software, so there is no oversampling, HDR or IF Filtering enabled. The RSPduo performs very well in most tests, but very poorly in the 5 kHz spacing test.
The rest of the paper covers the TX parameters, and we highly recommend going through and comparing the individual result graphs from each SDR test if you want more information and results from tests at different frequencies. The code and recorded data can also be found on the projects Gitlab page at https://gitlab.com/librespacefoundation/sdrmakerspace/sdreval.
SDRplay have recently released an update on how the Coronavirus is impacting their supply lines. In short, they note that their fulfillment is currently normal, but there may be delays in the logistics distribution network. In terms of stock levels, they have enough to cover a few more weeks of normal buying, but beyond that the supply chain is not certain and there may be restocking delays.
We have been fortunate that our suppliers have been able to source the components needed to fulfil our current backlog commitments. In particular the demand for the new RSPdx exceeded our expectations, and that has caused shortages up until now.
However we now have enough product available to continue supply of all three SDRplay production RSPs for a few more weeks at traditional buying levels. Beyond that, we will be dependent on our subcontract manufacturing partners’ ability to source components. As the coronavirus situation unfolds it is likely that restocking will take significantly longer than usual and we are working with both suppliers and our distributors to do our best to plan for the uncertain future.
Meanwhile, regarding orders placed in the next week or so, SDRplay and its fulfilment centres are currently working as normal, BUT please be aware that logistical delays in the distribution network are likely – so please be patient if your shipment takes longer than expected.
We’d also like to take the opportunity to send our best wishes to all our customers and their friends and families as this emergency situation develops.
Jon, on behalf of the SDRplay team.
Over on his YouTube channel TechMinds has uploaded a video reviewing the X1-HF 1 - 50 MHz Trapped Coil Receiving antenna from Moonraker.eu which goes for £69.95. This is a small electrically short antenna for HF reception which is easy to setup and install, requiring no radials. However, like all short HF antennas it is a compromise.
In the review he uses an SDRplay RSP2 SDR to test HF reception with the antenna. Later in the video he also tests it outside the advertised 1 - 50 MHz range. He concludes that the antenna works very well for it's small size.