Category: SDRplay

Testing VOR Navigation in the Stratosphere with an SDRplay RSP1 and High Altitude Balloon

Over on the SDRplay blog Jon has posted about the STRATONAV experiment which makes use of the SDRplay RSP1 software defined radio. The STRATONAV experiment uses high altitude balloons to carry the RSP1 as well and a commercial portable receiver. The two receivers were configured to receive aircraft VOR navigation signals in order to test the effectiveness of VOR when used at extreme altitudes of up to 28 km. The VOR navigational data was then compared against GPS tracks, resulting in a measure of how well VOR worked at those altitudes. 

VOR (aka VHF Omnidirectional Range) is a navigational beacon that is transmitted between 108 MHz and 117.95 MHz from a site usually at an airport. In the past we have posted about VOR a few times as it can also be decoded with an RTL-SDR, or used for passive doppler aircraft radar. 

The results showed that VOR navigation does indeed continue to function at extreme altitudes, proving that it can be used as a back up navigation system for stratospheric platforms. They also note that VOR navigation could also be used as a primary navigation system on smaller stratospheric platforms due to its low cost and low complexity to implement.

The full academic paper is available on sciencedirect, or for free via Sci-Hub.

SDRplay RSP1 (seen bottom right behind the metal mount) Flying on a High Altitude Balloon

RSGB Talk: How To Check and Report VDSL RFI with an SDR in the UK

Back in April we posted a video from Tech Minds where he showed us how to use special software combined with an SDRplay RSPdx to detect and report VDSL interference on the HF bands. 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.

Recently John Rogers (M0JAV) presented a talk via the UK amateur radio organization RSGB. In the talk he explains how VDSL works, why it causes RFI and how to check for VDSL RFI using an SDR and the Lelantos software. He also shows how he drove around with a magnetic loop antenna looking for VDSL RFI sources in his neighbourhood. He then goes on to call out for more volunteers in the UK to submit RFI reports to Ofcom as they responded that they won't do anything about the interference unless there are more complaints. 

The RSGB EMC Committee (EMCC) has been investigating VDSL interference since 2014. As the number of installations has risen to over 30M the interference level at amateur radio stations has also increased. The majority of radio amateurs are now impacted by this problem.

In the May 2020 RadCom we outlined how to detect and estimate the level of interference. This can be done by inspection of an SDR spectrum display or by taking a recording and then using a SW package—developed by Martin Sach of the EMCC—which identifies the VDSL signature in the recording and shows how many different VDSL lines are causing the problem and what their relative strengths are.

This talk demonstrates what to look for and how to use the tools to find out if you have a problem yourselves. We hope this will help you respond to our call for action and complain to Ofcom about the level of RFI you are subjected to.

John Rogers, M0JAV
Chair EMCC

RSGB Tonight @ 8 - How to check for VDSL RFI with John Rogers, M0JAV

TechMinds: Decoding HF ACARS HFDL with an SDRplay RSPdx

In his latest YouTube video Tech Minds shows how to decode HF ACARS (HFDL) with an SDRplay RSPdx. Tech Minds initially explains what HFDL is, and how it is typically received via special aviation radios. He goes on to show how we can decode it from home with any HF capable SDR, and a program called PC-HFDL. Finally he explains how to set up a Google Earth file that can display the aircraft location data that is provided in some HFDL messages.

Decoding High Frequency Data Link - HF ACARS HFDL

Tech Minds: Decoding GMDSS Maritime Distress Messages

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.

How To Decode Maritime Distress Messages GMDSS DSC

Techminds: Testing out the new Plugins Feature on SDRuno V1.4 RC1

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.

SDRPlay SDRuno Plugins Feature - NEW!

TechMinds: Detecting HF Interference from a VDSL Internet Connection

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.

VDSL RFI Detection and how to report it to OFCOM

TechMinds: Demonstrating the QT-DAB Digital Audio Broadcast Decoder

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.

DAB Radio Decoder For SDR (RTL_SDR - HACKRF - AIRSPY)

The SWLing Post Reviews the YouLoop Passive Loop Antenna

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.

YouLoop Portable Passive Magnetic Loop Antenna for HF and VHF
YouLoop Portable Passive Magnetic Loop Antenna for HF and VHF