Category: Amateur Radio

YouTube Talk: Evaluating 9 of the Best Single Board Computers for Ham Radio SDR Systems

Over on YouTube the Ham Radio 2.0 channel has recently uploaded a talk that Scotty Cowling (WA2DFI) did at the 2018 TAPR digital communications conference. His talk centers around single board computers and his findings on the nine best single board computers (SBC) for ham radio SDR setups.

Scotty's talk begins by discussing why you'd want to use SBCs in your ham radio SDR setup, and explains why you might want to place them with the SDR close to the antenna, and then distribute the data over ethernet cable. He then reviews 9 boards listed below: 

  • Hardkernel Odroid C1
  • Raspberry Pi 3B
  • Hardkernel Odroid XU4
  • ASUS Tinker S
  • FriendlyElec NanoPC-T4
  • Pine64 RockPro64
  • 96 Boards Mediatek X20
  • 96 Boards HiKey 960
  • UDOO X86 Ultra

The boards are compared against CPU clock speeds, architecture, cache, debut year, RAM, boot ROM, bus speeds, OS support, and more. Scotty also discusses the need for low latency operation, but is yet to compare this on the boards. The best value for money boards that Scotty recommends end up being the Odroid XU4, Tinkerboard, NanoPC-T4 and the RockPro64.

Ham Radio 2.0: Episode 151 - Evaluating 9 of the Best Single Board Computers for Modern SDR Systems

GammaRF: Distributed Radio Signal Collection and Analysis with RTL-SDR and HackRF

Thank you to Josh for submitting news about his project called GammaRF. GammaRF is an client-server program that is used to aggregate signal information via the internet from distributed SDRs. Currently the RTL-SDR and HackRF SDRs are supported.

ΓRF (“GammaRF”, or “GRF”) is a radio signal collection, storage, and analysis system based on inexpensive distributed nodes and a central server. Put another way, it is a distributed system for aggregating information about signals, and a back-end infrastructure for processing this collected information into coherent “products”.

Nodes utilize inexpensive hardware such as RTL-SDR and HackRF radios, and computers as small and inexpensive as Intel NUCs. Each node runs modules which provide various radio monitoring functionality, such as monitoring frequencies for “hits”, watching power levels, keeping track of aircraft (through ADS-B), and more. Nodes are distributed geographically and their data is combined on the server for hybrid analysis.

A web-based system allows users to view information from and about each station in its area. Below shows the server landing page. Markers are placed at each station’s last known location (stations can be mobile or stationary.)

GammaRF Server Landing Page
GammaRF Server Landing Page

From the currently implemented modules it appears that you can monitor ADS-B, scan and monitor the power of a set of frequencies, forward the output from trunk-recorder (a P25 call recorder), scan the spectrum and monitor power levels, monitor a single frequency for activity, take a picture of a swath of RF spectrum, and collect 433 MHz ISM data. Some example applications might include:

  • Monitoring ham radio activity on repeaters in a city
  • Creating timelines of emergency services activity in an area
  • Distributed tracking of satellites and other mobile emitters
  • Monitoring power at a frequency, for example as a mobile node traverses an area (e.g. signal source location)
  • Building direction finding networks (e.g. for fox hunts)
  • Spectrum enumeration (finding channels and guessing modulation) [under development]
Monitoring Activity of an Amateur Radio Repeater
Monitoring Activity of an Amateur Radio Repeater via the 'scanner' Module

Connecting an RTL-SDR Panadapter to a uBITX Transceiver

The uBITX is a US$129 HF SSB/CW QRP transceiver kit that works from 3 MHz to 30 MHz with up to 10W TX power. It's a fully analogue radio, but it can be combined with an RTL-SDR to create a panadapter display thanks to a tutorial released by KD8CEC.

The method requires that you use the custom CEC firmware, or modify other firmware,  as this appears to change the output frequency at the tap point. The tap point is made accessible by soldering on an extra SMA connector for the RTL-SDR to connect to. The rest of the work is entirely performed in the uBITX software manager, Omni-Rig and SDR-Console V3.

uBITX with RTL-SDR Panadapter
uBITX with RTL-SDR Panadapter

An Introduction to SDR and SDR Applications for Shortwave Listeners

Over on the SWLing Post blog, author Thomas Witherspoon K4SWL has uploaded a new article titled "Software Defined Radio Primer Part 1: Introduction to SDRs and SDR applications". The article originally appeared in the June 2018 issue of The Spectrum Monitor magazine, which can be purchased online for $3 per issue.

The idea behind the article is to introduce people to SDR from a shortwave listening point of view, so high performance HF SDRs like the Airspy HF+, Elad FDM-S2 and WinRadio Excalibur are discussed. Thomas notes that these SDRs can perform as well as traditional DX-grade receivers that can cost two to three times more. He also explains what advantages SDR's bring to the shortwave radio listening hobby. This may be a good article to show those still using older hardware radios that haven't yet converted to the SDR world. 

The article is currently part one of a three part series, with parts two and three to be released in October and November.

DXing with SDR in a Car
DXing with SDR in a Car (Photo: Guy Atkins)

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.

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

YouTube Talk: Evaluating 9 of the Best Single Board Computers for Ham Radio SDR Systems

Over on YouTube the Ham Radio 2.0 channel has recently uploaded a talk that Scotty Cowling (WA2DFI) did at the 2018 TAPR digital communications conference. His talk centers around single board computers and his findings on the nine best single board computers (SBC) for ham radio SDR setups.

Scotty's talk begins by discussing why you'd want to use SBCs in your ham radio SDR setup, and explains why you might want to place them with the SDR close to the antenna, and then distribute the data over ethernet cable. He then reviews 9 boards listed below: 

  • Hardkernel Odroid C1
  • Raspberry Pi 3B
  • Hardkernel Odroid XU4
  • ASUS Tinker S
  • FriendlyElec NanoPC-T4
  • Pine64 RockPro64
  • 96 Boards Mediatek X20
  • 96 Boards HiKey 960
  • UDOO X86 Ultra

The boards are compared against CPU clock speeds, architecture, cache, debut year, RAM, boot ROM, bus speeds, OS support, and more. Scotty also discusses the need for low latency operation, but is yet to compare this on the boards. The best value for money boards that Scotty recommends end up being the Odroid XU4, Tinkerboard, NanoPC-T4 and the RockPro64.

Ham Radio 2.0: Episode 151 - Evaluating 9 of the Best Single Board Computers for Modern SDR Systems

GammaRF: Distributed Radio Signal Collection and Analysis with RTL-SDR and HackRF

Thank you to Josh for submitting news about his project called GammaRF. GammaRF is an client-server program that is used to aggregate signal information via the internet from distributed SDRs. Currently the RTL-SDR and HackRF SDRs are supported.

ΓRF (“GammaRF”, or “GRF”) is a radio signal collection, storage, and analysis system based on inexpensive distributed nodes and a central server. Put another way, it is a distributed system for aggregating information about signals, and a back-end infrastructure for processing this collected information into coherent “products”.

Nodes utilize inexpensive hardware such as RTL-SDR and HackRF radios, and computers as small and inexpensive as Intel NUCs. Each node runs modules which provide various radio monitoring functionality, such as monitoring frequencies for “hits”, watching power levels, keeping track of aircraft (through ADS-B), and more. Nodes are distributed geographically and their data is combined on the server for hybrid analysis.

A web-based system allows users to view information from and about each station in its area. Below shows the server landing page. Markers are placed at each station’s last known location (stations can be mobile or stationary.)

GammaRF Server Landing Page
GammaRF Server Landing Page

From the currently implemented modules it appears that you can monitor ADS-B, scan and monitor the power of a set of frequencies, forward the output from trunk-recorder (a P25 call recorder), scan the spectrum and monitor power levels, monitor a single frequency for activity, take a picture of a swath of RF spectrum, and collect 433 MHz ISM data. Some example applications might include:

  • Monitoring ham radio activity on repeaters in a city
  • Creating timelines of emergency services activity in an area
  • Distributed tracking of satellites and other mobile emitters
  • Monitoring power at a frequency, for example as a mobile node traverses an area (e.g. signal source location)
  • Building direction finding networks (e.g. for fox hunts)
  • Spectrum enumeration (finding channels and guessing modulation) [under development]
Monitoring Activity of an Amateur Radio Repeater
Monitoring Activity of an Amateur Radio Repeater via the 'scanner' Module

Connecting an RTL-SDR Panadapter to a uBITX Transceiver

The uBITX is a US$129 HF SSB/CW QRP transceiver kit that works from 3 MHz to 30 MHz with up to 10W TX power. It's a fully analogue radio, but it can be combined with an RTL-SDR to create a panadapter display thanks to a tutorial released by KD8CEC.

The method requires that you use the custom CEC firmware, or modify other firmware,  as this appears to change the output frequency at the tap point. The tap point is made accessible by soldering on an extra SMA connector for the RTL-SDR to connect to. The rest of the work is entirely performed in the uBITX software manager, Omni-Rig and SDR-Console V3.

uBITX with RTL-SDR Panadapter
uBITX with RTL-SDR Panadapter

An Introduction to SDR and SDR Applications for Shortwave Listeners

Over on the SWLing Post blog, author Thomas Witherspoon K4SWL has uploaded a new article titled "Software Defined Radio Primer Part 1: Introduction to SDRs and SDR applications". The article originally appeared in the June 2018 issue of The Spectrum Monitor magazine, which can be purchased online for $3 per issue.

The idea behind the article is to introduce people to SDR from a shortwave listening point of view, so high performance HF SDRs like the Airspy HF+, Elad FDM-S2 and WinRadio Excalibur are discussed. Thomas notes that these SDRs can perform as well as traditional DX-grade receivers that can cost two to three times more. He also explains what advantages SDR's bring to the shortwave radio listening hobby. This may be a good article to show those still using older hardware radios that haven't yet converted to the SDR world. 

The article is currently part one of a three part series, with parts two and three to be released in October and November.

DXing with SDR in a Car
DXing with SDR in a Car (Photo: Guy Atkins)

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.

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

Using a Raspberry Pi 3, USB Soundcard, Speclab and Exagear to Detect SAQ VLF Transmissions

Thanks to DE8MSH for writing in about his project that involves using a Raspberry Pi 3 and cheap 7€ USB sound card connected to an old Grahn GS1 VLF antenna to detect the SAQ VLF station. Standard PC or USB sound cards can be used as a narrowband VLF capable SDR simply by connecting an antenna to the sound inputs. SAQ (aka Grimeton Radio Station) is a heritage VLF transmitter in Sweden that transmits CW at 17.2 kHz, normally only on Alexanderson Day and Christmas Day, but can sometimes unofficially transmit without announcement due to maintenance, training or local events.

In terms of software running on the Pi 3 DE8MSH uses Spectrum Laboratory (speclab) to monitor the sound card waterfall, and has written a Python script that uploads the processed images from speclab to a Twitter account every 20 minutes. This way he hopes to be able to detect any unannounced SAQ transmissions from his station in Sweden. 

Spectrum Laboratory is actually a Windows and x86 only program, however as shown in one of our previous posts, it is possible to use a special compatibility emulator called Exagear which allows you to run x86 programs on ARM hardware. Together with Wine you can then run x86 Windows programs on single board computers like the Raspberry Pi 3 which run Linux on ARM hardware.

Speclab Screenshot from DE8MSHs Pi3 soundcard monitoring system
Speclab Screenshot from DE8MSHs Pi3 soundcard monitoring system

Understanding Direction Finding on the KiwiSDR

Earlier this month we posted about the KiwiSDR direction finding update, which now allows anyone with internet access to utilize public KiwiSDR's for the purpose of pinpointing the physical location of a transmitter that transmits at a frequency below 30 MHz.

A few people have had trouble understanding how to use the direction finding feature, so KiwiSDR fan Nils Schiffhauer (DK8OK) has written up a KiwiSDR direction finding usage guide. Nils' guide explains the basic technical ideas behind the TDoA (Time Difference of Arrival) direction finding technique used, and highlights some important considerations to take into account in order to get the best results. For example he discusses best practices on how to choose receiver locations, how many receivers to choose, and how to properly take into account the time delaying effects of ionospheric propagation with HF signals.

Finally at the end of the document he shows multiple case studies on HF signals that he's managed to locate using the discussed best practices. Looking through these examples should help make it clear on how receiver locations should be chosen.

DK8OK Locates Radio France at 15320 kHz
DK8OK Locates Radio France at 15320 kHz