Decoding RDS (Radio Data System) from FM broadcast stations

This is another good use for the low cost RTL-SDR type of software defined radio equipment.

There is only one additional piece of software required, and that is:

SodiraSDR Software Radio by Bernd Reiser

Radio Data System, or 'RDS', is a communications protocol standard for embedding small amounts of digital information in conventional FM radio broadcasts.

It creates a standard format for a variety of information including time, station identification and program information.

It uses an error correcting method with a data speed of 1.1875 kb/s on a 57kHz subcarrier of the FM radio broadcast signal -  88-108 MHz range in the UK.

It is very easy to set up; the extracted folders and files can be placed wherever you like on your PC and only require a copy of the ExtIO_RTL2832.dll file for your RTL-SDR device being placed in the top level folder.

The software does a whole lot more than receive FM and decode RDS, and will work with Digital Radio Mondiale, or 'DRM' digital modes, AM and SSB too.

Unlike some of the other SDR projects I have played with, I found that I needed a relatively strong signal to see the RDS decoding. A typical FM stereo broadcast signal will have +/- 75kHz deviation and 15kHz audio response. That occupies 180kHz bandwidth. When you add the RDS signal, it extends it even further. I found a filter setting of 190kHz best.

Here are a couple of screenshots for the main waterfall window and the RDS decode window:

 Click on the images to see them full size! 😉

BARTG RTTY Sprint Contest - Jan 22/23 2022

I hadn't given my SCC callsign - G2B - an airing on digital modes for quite some time and so decided I would have a go at the BARTG RTTY Sprint contest on the HF bands over the weekend of January 22nd and 23rd 2022.

I can't imagine many radio operators who sit cross legged on the floor and use their rig(s) and a laptop computer perched precariously on a cardboard box ... but then it takes all sorts! 😆

I started at the competition kick-off time - 12 noon on the Saturday - and continued until about 6 p.m. The I rose early on the Sunday and was back on again at around 5 a.m.

This turned out to be a bit of wishful thinking as things didn't really get underway - for me at least - until about 6:45 a.m. and I was wishing I had perhaps been better in having a lie-in! 😴

Most of my activity was with European stations, but I did manage to make it into North America on 4 occasions and - out of the blue - Uruguay!

The set-up is very simple ... FT817ND and fldigi; that's all. I used 40, 20 and 15 metre bands and indoor dipoles.

I always have a bit of fun and games when it comes to uploading the logfile. I haven't invested in any additional software so make do with what fldigi can provide in the way of a Cabrillo file, and then make any amendments in Excel and Notepad.

 

  Click on the image to see it full size! 😉

 

Little piece about QRP HF working in RadCom

Recently a new gentleman - Daimon Tilley/G4USI - took over the role of putting together the 'HF' column in RadCom magazine.

I thought I'd like to share - as I try to as often as possible - just how well it is possible to make contacts using low power and a compromised antenna set-up.

I find this works best with the digital modes - including machine generated ones - but it's also feasible with voice communications too.

 Click on the images to see them full size! 😉

 

 

 

ADS-B - Decoding and displaying aircraft tracking data

I've been interested, for a long time, in watching the various websites showing aircraft data in real time, but not got around to doing it directly with an SDR, relevant applications and a suitable antenna.

After investigating what programmes were available for the Windows environment, I chose:

• RTL1090
  
  RTL1090 is a non tunable 1090 MHz receiver application for Mode-A/C or Mode-S transmissions.
  
  Mode A equipment transmits an identifying code only.
  Mode C equipment enables the air traffic controller see the aircraft altitude or flight level automatically.
  Mode S equipment has altitude capability and also permits data exchange.
  
  ADS-B (Automatic Dependent Surveillance Broadcast) is a technique that relies on aircraft or airport vehicles broadcasting their identity, position and other information derived from on board systems (GNSS etc.)
  
  This signal can be captured for surveillance purposes on the ground (ADS-B Out) or on board other aircraft in order to facilitate airborne traffic situational awareness, spacing, separation and self-separation (ADS-B In).
  
  
• Virtual Radar Server
  
  Virtual Radar Server is an open-source .NET application that runs a local web server.
  
  You can connect to the web server with any up to date browser and see the aircraft plotted on a map.

After configurations, these applications receive the local ADB-S 'S' mode transmissions and show aircraft details as a map overlay. The end effect is virtually identical to the web based and mobile 'phone based views, except for not needing an Internet connection and only being able to see a limited number of aircraft dependent on the antenna gain and location.

With an internal HB9CV - cut for 70 cm ! - I was still able to see plots up to around 40 miles distance:

Click on the image to see it full size! 😉

Decoding telemetry data from satellites 🚀

Here, to date, are the screen shots of the decoded telemetry data that I've been able to receive from a small range of satellites.

• CAS-9/XW-3/HO-113 was launched from the Taiyuan Satellite Launch Centre in China.

It carries a CW telemetry beacon, GMSK telemetry data transmission, V/U mode linear transponder for SSB and CW, a visible light band space camera and an experimental thermoelectric generator for high school students.

It took several attempts to obtain a strong enough signal for decodable data; an 84 degree pass finally produced the necessary results. 😊

The decoded data I received was as follows: 

 Click on the images to see them full size! 😉 

There may be an issue with with SWR - note the forward and reflected power levels which give a calculated figure of about 5.5:1.

• The Bobcat-1 satellite was developed at the Ohio University Avionics Engineering Centre and launched on October 2nd 2020 and deployed into orbit from the ISS on November 5, 2020.

It is a 3U cubesat deployed to study Global Navigation Satellite Systems (GNSS). As implied, the global network includes Europe’s Galileo, the USA’s NAVSTAR GPS system, Russia’s GLONASS and China’s BeiDou Navigation Satellite System. Studies will hopefully improve the availability and performance of these navigation systems for other satellites and spacecraft.

It will probably de-orbit sometime early in 2022.

 

• The KSU-Cubesat (King Saud University Cubesat) is a 1U cubesat which was developed by students and researchers of the College of Engineering at King Saud University, Saudi Arabia.
  
  It was launched on March 22nd 2021 from Kazakhstan and takes photographs of the Earth, moon and space and sends the images to the College ground station.

• JAISAT-1 (Joint Academy for Intelligent Satellites for Amateur Radio of Thailand) - a 3U cubesat - was launched on July 5th 2019.  It is Thailand's first amateur radio satellite.
  
  The JAISAT-1 Beacon signal is on 435.700 MHz in GMSK Mobitex 4800 bps and it carries an amateur radio 2m to 70 cm linear transponder for SSB and CW communications.

ARISS SSTV 'Lunar Exploration' Awards - Dec 2021 Event!

For the ARISS SSTV December 26th to 31st 2021 event from the International Space Station; there were a whole host of award certificates.

Here are the award certificates from a whole range of groups; all of whom obviously take a great deal of effort in producing such excellent works of art!

Click on the images to see them full size! 😉

The one above is a bit different in that it is awarded for gaining
5 certificates from a requisite awards list!