Category: Amateur Radio

RTL-SDRs and the VHF+ Reverse Beacon Network

The Reverse Beacon Network is a project that monitors the amateur radio bands by using volunteer stations to continuously and autonomously collect data on what/when stations are being received, and how good the signal is. The data is made public on the internet and this allows amateur radio operators to easily determine overall propagation conditions. It is currently working mostly with CW (morse code) stations, and mostly on HF, although it is expanding to VHF+ as explained below.

During October, John Ackermann (N8UR) did a talk at the "Microwave Update 2018" conference held in Dayton, Ohio. His talk was about setting up a VHF+ reverse beacon network monitoring station, using multiple RTL-SDR dongles for monitoring. The RTL-SDR dongles run on a Raspberry Pi which runs the rtl_hpsdr software. This allows multiple RTL-SDR dongles to emulate a multi-band HPSDR receiver over Ethernet. They can then be accessed on a PC by the CW Skimmer program which decodes the received CW signals, and then logs it online on the reverse beacon network's website.

The talk slides can be found here, and the video is shown below. More talks from the conference can be found on this YouTube playlist.

Four RTL-SDR.COM V3 dongles used in a VHF+ Reverse Network Setup
Four RTL-SDR.COM V3 dongles used in a VHF+ Reverse Network Setup

John Ackermann, N8UR - The VHF+ Reverse Beacon Network

Amazon AWS Satellite Ground Stations Now Available For Hire

Over on the AWS blog Jeff Barr has blogged about Amazon's new rentable ground station system called "AWS Ground Station". AWS, or Amazon Web Services is the server farm division of Amazon. They allow customers to rent out server capability on demand. In a similar sense, AWS Ground Station is aiming to allow customers to rent out satellite ground stations on demand.

Launching low cost micro/nano satellites has become very affordable in recent years and it's now common to see high schools, colleges, organizations and hobbyists designing, fabricating and launching their own satellites. Once launched, a ground station is required to receive the satellite's radio transmission as it passes over. Most low cost satellite owners will not have the budget to deploy ground stations all around the world for continuous monitoring of the satellite. This is where AWS Ground Station can take over, allowing a ground station on the other side of the world to be rented temporarily during a pass.

Currently the service is just starting, and only has 2 ground stations, but by 2019 they hope to have a total of 12. More information available on the official AWS Ground Station website.

Alternatively, there are other free open source services that could be utilized such as SATNOGS. SATNOGs relies on volunteer ground stations running antenna rotators that can be built with a 3D printer, some low cost motors and electronics, and an RTL-SDR. The antenna rotator carries a Yagi antenna and will automatically track, receive and upload satellite data to the internet for the public to access.

AWS Ground Station Web Site
AWS Ground Station Web Site

Es’hail-2: First Geostationary Satellite with Amateur Radio Transponders Successfully Deployed

Today SpaceX have successfully launched and deployed the Es'hail-2 satellite which is now in geostationary orbit. This launch is special for amateur radio enthusiasts because it is the first geostationary satellite that contains an amateur radio transponder on it. The satellite is positioned at 25.5°E which is over Africa. It will cover Africa, Europe, the Middle East, India, eastern Brazil and the west half of Russia/Asia. Unfortunately, North America, Japan, most of South America, Australia and NZ miss out.

Coverage of Es'hail 2
Coverage of Es'hail 2

The satellite has a two bandwidth segments, a 250 kHz narrow band for modes like SSB, FreeDV, CW, RTTY etc, and a 8 MHz wide band for digital amateur TV (DATV) modes like DVB-S and DVB-T.

The downlink frequencies are at 10 GHz so a low cost TV LNB could be used as the antenna. For receiving the narrowband modes, an RTL-SDR or similar SDR could be used, and for the 8 MHz DATV modes a standard DVB-S2 set top box can be used to receive and decode the video. For uplink, the transmission frequency is at 2.4 GHz.

According to the commissioning order of the satellite, it is expected that the AMSAT transponders will be activated only after all tests have been passed, and after other higher priority commercial telecommunications systems have been activated. This is expected to take about 1-2 months.

2018: Es'hail-2 and its amateur radio payload - Graham Shirville (G3VZV) & Dave Crump (G8GKQ)

A Tutorial on Receiving HF SSTV with a Raspberry Pi and RTL-SDR V3

Thank you to Giuseppe (IT9YBG) who has written in to share his tutorial about setting up a direct sampling RTL-SDR V3 based SSTV receiver on a Raspberry Pi. He writes that he uses the receiver to continuously receive images at 14.230 MHz, but with a frequency tweak in the command line code the system could also be used to receive the VHF SSTV images sent by the ISS.

In the tutorial he uses the free QSSTV software for decoding. An RTL-SDR together with the CSDR DSP software is used to set up a command line based receiver, which pipes the SSTV audio into a virtual audio sink, and then into QSSTV. The receiver setup procedure is similar to the method used in our RTL-SDR V3 QRP monitoring station tutorial, and is a very nice way of setting up an efficient command line based RTL-SDR audio output.

QSSTV Running on a Raspberry Pi with RTL-SDR V3 Radio
QSSTV Running on a Raspberry Pi with RTL-SDR V3 Radio

Combining HRPT Images From Germany to Canada

HRPT is a high resolution weather satellite image that is broadcast by the NOAA satellites. Receiving HRPT weather satellite signals is a little different to the more commonly received NOAA APT or Meteor M2 LRPT images which most readers may already be familiar with. HRPT is broadcast by the same NOAA satellites that provide the APT signal at 137 MHz, but is found in the L-band at around 1.7 GHz. The signal is much weaker, so a high gain dish antenna with motorized tracking mount, LNA and high bandwidth SDR like an Airspy is required. The payoff is that HRPT images are much higher in resolution compared to APT.

Manuel aka Tysonpower on YouTube has been successfully receiving these HRPT images for some time now and recently had the idea to try and combine two HRPT images together to create one big image covering the Atlantic ocean.

Manuel lives in Germany and on Twitter he found that he had a follower in Canada who was also receiving HRPT images. So he asked his follower to provide him with HRPT weather images that were received shortly after the pass in Germany. He then stitched the images together, and color corrected them which resulted in a nice large image covering Europe, the Atlantic, Canada and Florida.

[EN subs] HRPT over The Ocean - Ein Bild von Köln nach Kanada

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