Category: Digital Signals

Creating a Wireless Pi-Star Nextion Display for Amateur Digital Radio

Thanks to Steve K2GOG of The Hudson Valley Digital Network (HVDN) for submitting his post on how to create a wireless display for Pi-Star. Pi-Star is a pre-built Raspberry Pi image for amateur radio users experimenting with digital voice communications like D-STAR and DMR. They write that it can be used for applications such as a "single mode hotspot running simplex providing you with access to the increasing number of Digital Voice networks, [or a] public duplex multimode repeater".

Pi-Star is compatible with serial based LED displays with built in GUIs like the Nextion. The displays are usually connected directly to the Raspberry Pi, but Steve wanted to use the display remotely. To do this he used a simple and inexpensive 70cm band HC-12 wireless serial port adapter. With the wireless adapters connected to the Pi he was able to see the pulses in SDR# via his RTL-SDR to confirm that the wireless serial signal was being sent. He then connected the second wireless adapter to the Nextion display via a few diodes to drop the voltage, and was able to get the display updating as if it was connected directly.

In the post Steve mentions that HVDN are also giving away an HC-12 and RTL-SDR to the first person to submit some progress with this idea.

Creating a wireless Nextion Display for Pi-Star.
Creating a wireless Nextion Display for Pi-Star.

SDR# Inmarsat Decoder Plugin Now Available

Microp11, the programmer of Scytale-C a standalone Inmarsat decoder has just released a new Inmarsat decoder SDR# plugin. The plugin is currently in the "pre-alpha" stages, so is still missing some functionality and may be buggy. However, it does appear to be functional at this point in time. It can be used with RTL-SDRs, and any other SDR# compatible SDR including units running on remote SpyServers. Microp11 writes:

  • I ran it with SDR# version v1.0.0.1761.
  • If it crashes you SDR# I apologize in advance.
  • The auto-tracking (default on) will alter your SDR# frequency and follow the signal’s CF. When the SNR is very low, please disable it and manually tune the SDR# to try to get the CF as close to 2000 as possible.The demodulator still has plenty ideas of its own.
  • Use USB mode with 4000 Hz bandwidth.
  • For now the interface is missing the usual scatter plots.
  • UDP Address and UDP Port are for sending the decoded frames to the Scytale-C UI.
  • Offset and CF are the difference from zero error and the CF frequency of the demodulated BPSK signal.
  • Tx and SYM are the transmitted over UDP frames and SYM is showing the number of demodulated symbols.
  • A bunch of libraries are attached as extra files. Please be gentle and accept the package as it. Will clean-up in the future.
  • Use in conjunction with the Scytale-C UI from the archive: “x64-UI1.6-Decoder1.4.zip” (link below)
  • The magic line is included in the archive: “SDRSharp.ScytaleC-1.0-alpha.zip”

The files can be downloaded from https://bitbucket.org/scytalec/scytalec/downloads.

SDRSharp Scytale-C Plugin
SDRSharp Scytale-C Plugin

Transmitting and Receiving DATV with a LimeSDR and a Modified $20 DVB-S Receiver

Over on YouTube user Corrosive has uploaded a video showing how he can use the recently updated DATV Express software to transmit Digital Amateur TV (DATV) with a LimeSDR Mini, and receive it with a cheap US$20 DVB-S satellite set top box that he's modified with a custom firmware update. Corrosives work is excellent as it allows anyone to get started in DATV amateur radio cheaply. He writes:

Last week I noticed the windows DATV express software for windows had been updated to include several SDR platforms [appears to now support the LimeSDR and LimeSDR Mini, as well as the PlutoSDR] https://www.datv-express.com/CustomPage/Downloads

Using my new LimeSDR Mini I wanted to try this out. I went online and purchased a cheap DVB-S Satellite set top box on eBay branded as a KOQIT K1Mini.

In order to allow the KOQIT K1Mini DVB-S set top box to receive DATV frequencies, Corrosive has released a firmware update on GitHub that removes all satellites listed in the receiver, and replaces it with six DATV channels for amateur television use. He writes:

I decided to split the 3 23cm ATV frequencies into 6 at half the bandwidth for digital.

The receiver with my firmware configures the device to see a 9750LO LNB, by placing a simple antenna on the receiver instead of an LNB the 1.2 ghz amateur frequencies are shifted by 9750mhz and can be scanned as if they were a satellite transponder.

If you don't have a TX capable or DATV Express compatible SDR like the LimeSDR or Pluto, then we note that RPiTX (software that allows a Raspberry Pi to transmit RF without any additional hardware) also has DATV transmit capabilities that could in used in their place.

Digital DVB-S Amateur Television Station With LimeSDR Mini and a Satellite Receiver 23CM 1.2GHz

datv_limesdr_koqit_corrosive
datv_limesdr_koqitdvbs

Creating a Wireless Pi-Star Nextion Display for Amateur Digital Radio

Thanks to Steve K2GOG of The Hudson Valley Digital Network (HVDN) for submitting his post on how to create a wireless display for Pi-Star. Pi-Star is a pre-built Raspberry Pi image for amateur radio users experimenting with digital voice communications like D-STAR and DMR. They write that it can be used for applications such as a "single mode hotspot running simplex providing you with access to the increasing number of Digital Voice networks, [or a] public duplex multimode repeater".

Pi-Star is compatible with serial based LED displays with built in GUIs like the Nextion. The displays are usually connected directly to the Raspberry Pi, but Steve wanted to use the display remotely. To do this he used a simple and inexpensive 70cm band HC-12 wireless serial port adapter. With the wireless adapters connected to the Pi he was able to see the pulses in SDR# via his RTL-SDR to confirm that the wireless serial signal was being sent. He then connected the second wireless adapter to the Nextion display via a few diodes to drop the voltage, and was able to get the display updating as if it was connected directly.

In the post Steve mentions that HVDN are also giving away an HC-12 and RTL-SDR to the first person to submit some progress with this idea.

Creating a wireless Nextion Display for Pi-Star.
Creating a wireless Nextion Display for Pi-Star.

SDR# Inmarsat Decoder Plugin Now Available

Microp11, the programmer of Scytale-C a standalone Inmarsat decoder has just released a new Inmarsat decoder SDR# plugin. The plugin is currently in the "pre-alpha" stages, so is still missing some functionality and may be buggy. However, it does appear to be functional at this point in time. It can be used with RTL-SDRs, and any other SDR# compatible SDR including units running on remote SpyServers. Microp11 writes:

  • I ran it with SDR# version v1.0.0.1761.
  • If it crashes you SDR# I apologize in advance.
  • The auto-tracking (default on) will alter your SDR# frequency and follow the signal’s CF. When the SNR is very low, please disable it and manually tune the SDR# to try to get the CF as close to 2000 as possible.The demodulator still has plenty ideas of its own.
  • Use USB mode with 4000 Hz bandwidth.
  • For now the interface is missing the usual scatter plots.
  • UDP Address and UDP Port are for sending the decoded frames to the Scytale-C UI.
  • Offset and CF are the difference from zero error and the CF frequency of the demodulated BPSK signal.
  • Tx and SYM are the transmitted over UDP frames and SYM is showing the number of demodulated symbols.
  • A bunch of libraries are attached as extra files. Please be gentle and accept the package as it. Will clean-up in the future.
  • Use in conjunction with the Scytale-C UI from the archive: “x64-UI1.6-Decoder1.4.zip” (link below)
  • The magic line is included in the archive: “SDRSharp.ScytaleC-1.0-alpha.zip”

The files can be downloaded from https://bitbucket.org/scytalec/scytalec/downloads.

SDRSharp Scytale-C Plugin
SDRSharp Scytale-C Plugin

Transmitting and Receiving DATV with a LimeSDR and a Modified $20 DVB-S Receiver

Over on YouTube user Corrosive has uploaded a video showing how he can use the recently updated DATV Express software to transmit Digital Amateur TV (DATV) with a LimeSDR Mini, and receive it with a cheap US$20 DVB-S satellite set top box that he's modified with a custom firmware update. Corrosives work is excellent as it allows anyone to get started in DATV amateur radio cheaply. He writes:

Last week I noticed the windows DATV express software for windows had been updated to include several SDR platforms [appears to now support the LimeSDR and LimeSDR Mini, as well as the PlutoSDR] https://www.datv-express.com/CustomPage/Downloads

Using my new LimeSDR Mini I wanted to try this out. I went online and purchased a cheap DVB-S Satellite set top box on eBay branded as a KOQIT K1Mini.

In order to allow the KOQIT K1Mini DVB-S set top box to receive DATV frequencies, Corrosive has released a firmware update on GitHub that removes all satellites listed in the receiver, and replaces it with six DATV channels for amateur television use. He writes:

I decided to split the 3 23cm ATV frequencies into 6 at half the bandwidth for digital.

The receiver with my firmware configures the device to see a 9750LO LNB, by placing a simple antenna on the receiver instead of an LNB the 1.2 ghz amateur frequencies are shifted by 9750mhz and can be scanned as if they were a satellite transponder.

If you don't have a TX capable or DATV Express compatible SDR like the LimeSDR or Pluto, then we note that RPiTX (software that allows a Raspberry Pi to transmit RF without any additional hardware) also has DATV transmit capabilities that could in used in their place.

Digital DVB-S Amateur Television Station With LimeSDR Mini and a Satellite Receiver 23CM 1.2GHz

datv_limesdr_koqit_corrosive
datv_limesdr_koqitdvbs

Listening To Multiple DMR Channels with DSD+ and a HackRF on Linux

Thanks to Tony C who wrote in and wanted to share a method that he's found to listen to  multiple DMR digital voice channels in Linux. DSD+ is a Windows program that can be used to decode DMR. Although for Windows it is possible to use in Linux via the emulator known as Wine, and pipe the digital audio to it from GQRX. In the quote below, DSD+ "FL" is short for "Fast Lane" which is DSD+'s paid beta service that you can join to get  newer code with more features. Tony writes:

I believe that can bridge the gap between using Linux with the ease of use programs of windows. As I am sure we both can attest that setting up trunk tracking / anything SDR is not as easy on Linux as it is on windows. For example, DSDplus FL makes it extremely easy to identify/decode DMR networks. There are similar things that can be done on Linux, but as I stated, it isn’t as easy to setup.

So the method that I setup and have been using successfully, using Ubuntu and a HackRF, setting up DSDplus 2.98 on wine, that gets audio piped from GQRX using a virtual sink as outlined in https://www.hagensieker.com/wordpress/2018/04/29/dsd-in-ubuntu-18-04/. It was a great blog, but I felt that it was incomplete when trying to get all the voice traffic passed on a network, as it only works on 1 channel at a time.

So I found the control channel for the network and created 5 bookmarks in GQRX and gave them the tag “DMR”. From there I downloaded gqrx scanner https://github.com/neural75/gqrx-scanner followed the install and setup instructions. From there I activated the scanner and GQRX will cycle through the frequencies and when voice traffic is passed, it will stop, and DSDPLUS via wine will decode and record the audio.

[The screenshot] example was for P25, but it has worked in connect+ as well, the only thing is that you cannot bookmark the control channel. I know other options exist out there such as SDRtrunk / op25 which I have used, but I believe this provides a good alternative to those who have used windows and are comfortable with the ease of use of dsdplus FL but want to be on the Linux OS. 

DSD+ Decoding Multiple DMR Channels on Linux
DSD+ Decoding Multiple DMR Channels on Linux

 

A Web and RTL-SDR Based Trunking Scanner

During the Cyberspectrum Wireless Village talks a few days ago Gavin Rozzi gave a talk about his online RTLSDR-based trunking scanner website at ocradio.live. Recently he wrote in and wanted to share a little more about his system. He writes:

[The talk focuses] on my experience implementing several open source software packages to create an online RTLSDR-based trunking scanner website, https://ocradio.live/ that serves the part of New Jersey that I live in. Using multiple RTLSDR receiving locations, the site is demodulating, recording, and timeshifting multiple talkgroups of local and state trunked radio systems to create a live streaming service and archive of past scanner calls. Data from the site is also accessible over a REST API and we allow the creation of custom scan lists. My presentation is going to center on the advantages the site has over traditional hardware scanners and some of the technical challenges that we had to overcome to get the project off the ground.

In the Cyberspectrum YouTube video, Gavin's talk starts at around 2:40:22 and his slides are available at https://cyberspectrum23.ocradio.live

OCRadio Streams Screenshot
OCRadio Streams Screenshot

Tutorial on using RS to Decode and Plot Radiosondes

A radiosonde is a small weather sensor package that is typically attached to a weather balloon. As it rises into the atmosphere it measures parameters such as temperature, humidity, pressure, GPS location etc, and transmits this data back down to a receiver base station using a radio signal.

Zilog's RS is a free open source radiosonde decoder for Linux and it supports a wide range of radiosonde protocols. Together with an RTL-SDR it is possible to receive radiosonde signals, and decode them using RS.

Over on his website, happysat has recently uploaded a tutorial that shows how to use RS with an RTL-SDR, CubicSDR or GQRX, and FoxtrotGPS, a GPS plotting program for visualizing the location of the radiosonde. The tutorial covers some tricky points like setting up audio piping in Linux, and getting the GPS data into a virtual COM port to use with FoxtrotGPS.

Alternatively, there are also Windows GUI based sonde decoders that can be used with the RTL-SDR such as SondeMonitor which costs 25 Euros, but also covers a wide range of sonde protocols, and RS41 Decoder which is a GUI for the RS41 sonde protocol only. If you are interested we have a tutorial on setting up radiosonde decoding in Windows with SondeMonitor available here.

Plotting the Sonde Location with an RTL-SDR, GQRX, RS and FoxtrotGPS.
Plotting the Sonde Location with an RTL-SDR, GQRX, RS and FoxtrotGPS.

Tutorial on Setting up OP25 for P25 Phase 2 Digital Voice Decoding

Most police departments is the USA have now upgraded or are in the process of upgrading their radio systems to P25 Phase 2 digital radio. The frequencies can easily be received with an RTL-SDR, but a decoder is required to be able to actually listen to the voice. Software like SDRTrunk and DSDPlus can decode P25 Phase 1, but at the moment the only software that is capable of decoding P25 Phase 1 AND 2 is a program called OP25. However, OP25 has a reputation of being fairly difficult to set up as it does not have a simple to use GUI, and requires Linux.

Over on John's Tech Blog, John has uploaded a very helpful step by step tutorial that should help with those trying to get OP25 to work. The tutorial assumes that you have Ubuntu 18.04 already installed, and then starts from downloading and installing OP25. The next steps involve setting up OP25 for the particular system in your area, which mostly involves just editing a spreadsheet to input frequency data from radioreference.com. John also mentions that he's been able to get OP25 running perfectly on a Raspberry Pi 3 B+ as well, with less than 40% CPU usage.

OP25 Running
OP25 Running

In the video below John reviews some of the steps, and shows OP25 running and decoding voice.

OP25 Tracking 2 Control Channels

Video Tutorial About Decoding 433 MHz ISM Devices with rtl_433

Over on his YouTube channel Tech Minds has recently uploaded a video that demonstrates and shows how to use the rtl_433 software with an RTL-SDR to decode 433 MHz ISM band low power devices. Typically these devices include things like home wireless temperature and weather sensors, tire pressure sensors, remote controls, and other various sensors.

In the video he sets up an RTL-SDR and magmount antenna by his window and is able to receive data from several of his neighbors weather stations, and some car key remotes. He shows how to run the software on both Linux and on Windows.

How To Decode 433Mhz Low Power Devices Using RTL433 And A RTL-SDR Receiver