Category: Antennas

Using a 25 Meter Radio Dish and an RTL-SDR as a SatNOGS Ground Station

SatNOGS is an open source project that aims to make it easy for volunteers to build and run RTL-SDR or other SDR based RF ground stations that automatically monitor satellites, and upload that data to the internet for public access. The antennas used in a typical home based SatNOGS station are small enough for a single person to handle, however recently the SatNOGS team have been working on setting up a monitoring station at the Dwingeloo Radio Observatory in the Netherlands.

Dwingeloo has a large 25 meter satellite dish antenna, and they connect it to an RTL-SDR on a laptop running the SatNOGS software. In the video they show it tracking the PRISM amateur radio satellite, and note that the use of this large dish will only be used in special circumstances. They write:

This week the Dwingelooradio Observatory tested their 25 meter dish as a SatNOGS station! Although not set up as a permanent SatNOGS station it is great to see this historic observatory linked to the network. Dwingeloo radio observatory was built between 1954 and 1956 near the village of Dwingeloo in the Netherlands. Since 2009 this single 25 meter dish has been a national heritage site.

Dwingeloo Radio Observatory as a SatNOGS 📡 station

Dwingleloo Satellite Antenna in the Netherlands
Dwingleloo Satellite Antenna in the Netherlands [Source: Wikipedia]

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

Element14 Video on Setting up a Portable Raspberry Pi & RTL-SDR Based NOAA Weather Satellite Receiver

Electronics distributor element14 has uploaded a video to their 'element14 presents' YouTube channel showing presenter Matt building and setting up a portable Raspberry Pi & RTL-SDR based NOAA weather satellite receiver. More information is also available on their supplemental content page.

The build consists of a Raspberry Pi, RTL-SDR and QFH antenna as the basic components. However, it is made into a very nice portable unit by using a stripped down LCD monitor placed into a heavy duty waterproof brief case. The whole thing is powered via a PC power supply. After the build is completed, Matt leaves the case on the roof for a few days collecting images.

Emboldened by the success of his Raspberry PIrate radio, Matt indulges in some more radio hacking by building a specialized QFH antenna and a briefcase form-factor satellite receiver in an attempt to intercept "faxes" from OUTER SPAACEEE!!! Connect with Matt on the element14 community: http://bit.ly/2RiSXC5

Project TIROS is a self-contained, Raspberry Pi-based satellite signal reception system designed to automatically download images and data from NOAA's POES spacecraft as they pass overhead and display the data on an integrated LCD panel. In this video, Matt will walk through how to set up an RTL-SDR module with a Raspberry Pi for automated satellite downloads as well as how to design and build a quadrifilar helical antenna for polar-orbiting signal reception.

Raspberry Pi NOAA Satellite Receiver

Designing and Testing a PCB Wideband Spiral Antenna

Back in January we posted about a Vivaldi antenna project by "hexandflex". In that project he showed how he designed and manufactured the Vivaldi. A Vivaldi antenna is wideband and directional and the design works well for frequencies above 800 MHz, but becomes too physically large to handle for lower frequencies like 400 MHz. In his latest project, hexandflex has designed a PCB based spiral antenna to cover these lower frequencies.

Hexandflex's post is split into three parts. The first post introduces us to his motivation and talks about what spiral antennas are. The second post discusses the modelling and simulation of the antenna with OpenEMS. OpenEMS is a free front end for MATLAB or Octave which allows you to simulate antenna parameters such as impedance and radiation pattern. Finally in the third post the real world parameters of the antenna are determined in an anechoic chamber owned by Antenna Test Lab, a professional antenna testing agency.

Hexandflex is currently selling his spiral antennas over on Tindie. There are two versions, one smaller one costing $32 designed for 800 MHz+ and a larger one costing $42 designed for 300 MHz+. Both come with suction cups that allow for easy window mounting.

The 800 MHz+ and 300 MHz+ spiral antennas by Hexandflex
The 800 MHz+ and 300 MHz+ spiral antennas by Hexandflex

RPiTX v2 Released: Easily Record and Replay with RTL-SDR and a Raspberry Pi

RPiTX is software for the Raspberry Pi which can turn it into a 5 kHz to 1500 MHz transmitter which can transmit any arbitrary signal. In order to transmit the software does not require any additional hardware apart from a wire plugged into a GPIO pin on the expansion header. It works by modulating the GPIO pin with square waves in such a way that the desired signal is generated. However, although additional hardware isn't required, if RPiTX is to be used in any actual application a band-pass filter is highly recommended in order to remove any harmonics which could interfere and jam other radio systems.

Earlier this month RPiTX was upgraded to version 2. One of the changes is a new GUI for testing the various transmission modes. Currently it is possible to transmit a chirp, FM with RDS, USB, SSTV, Opera, Pocsag, SSTV, Freedv. There is also a spectrum painter which allows you to display an image on a SDR's waterfall.

The RPiTX V2 GUI
The RPiTX V2 GUI
Painting an Image on a SDR Waterfall Display with RPiTX v2
Painting an Image on a SDR Waterfall Display with RPiTX v2

The RPiTX v2 update also makes recording a signal with an RTL-SDR, and replaying that signal with RPiTX significantly easier. Previously it was necessary to go through a bunch of preprocessing steps (as described in our previous tutorial) in order to get a transmittable file, but now RPiTX is capable of transmitting a recorded IQ file directly. This makes copying things like 433 MHz ISM band remotes significantly easier. One application might be to use RPiTX as an internet connected home automation tool which could control all your wireless devices.

Finally, another application of the RPiTX and RTL-SDR combination is a live RF relay. The software is able to receive a signal at one frequency from the RTL-SDR, and then re-transmit it at another frequency in real time. Additionally, it is also capable of live transmodulation, where it receives an FM radio station, demodulates and then remodulates it as SSB to transmit on another frequency.

The RPiTX V2 RTL-SDR Menu
The RPiTX V2 RTL-SDR Menu
RPiTX v2 re-transmitting a broadcast FM signal live at 434 MHz.
RPiTX v2 re-transmitting a broadcast FM signal live at 434 MHz.

Constructing a 3D Printed Wideband 900 MHz to 11 GHz Antenna

Thanks to Professor John Jackson of JR Magnetics for writing in and sharing his design for a 3D printed wideband antenna designed for 50 Ohm 900 MHz to 11 GHz operation.

John required a wideband antenna that could cover the cellphone bands, WiFi, Bluetooth up to 6 GHz and the new USB band from 5 GHz to 10 GHz all in a single antenna installation. He also needed the impedance to be as flat as possible to reduce signal pulse distortion. First he looked into classic discone and sphere antenna designs, but found that while a sphere had the required bandwidth, it did not have the desired impedance characteristics, and a discone had the desired impedance characteristics, but not the ultra wide bandwidth required.

To get around this John combines the sphere and discone designs together to create a sort of icecream with cone looking shape. This results in the ultra wide bandwidth required, and a relatively flat SWR that stays below 2.

The design is easily reproducible by anyone with a metal 3D printer. The antenna's top hemisphere and cone are printed in brass, whilst the radome and supporting structure are printed in plastic.

We have uploaded John's original document here (pdf warning), and display some of the images below. The full build instructions can be found on his website, and John is also selling the 3D printed parts via Shapeways.

jran900-top
jran900-bottom
jran900-radome
JRAN900-mount
jran900-swr
sphere-cone-ant-geo
jran-proto-bw-175

Using a 25 Meter Radio Dish and an RTL-SDR as a SatNOGS Ground Station

SatNOGS is an open source project that aims to make it easy for volunteers to build and run RTL-SDR or other SDR based RF ground stations that automatically monitor satellites, and upload that data to the internet for public access. The antennas used in a typical home based SatNOGS station are small enough for a single person to handle, however recently the SatNOGS team have been working on setting up a monitoring station at the Dwingeloo Radio Observatory in the Netherlands.

Dwingeloo has a large 25 meter satellite dish antenna, and they connect it to an RTL-SDR on a laptop running the SatNOGS software. In the video they show it tracking the PRISM amateur radio satellite, and note that the use of this large dish will only be used in special circumstances. They write:

This week the Dwingelooradio Observatory tested their 25 meter dish as a SatNOGS station! Although not set up as a permanent SatNOGS station it is great to see this historic observatory linked to the network. Dwingeloo radio observatory was built between 1954 and 1956 near the village of Dwingeloo in the Netherlands. Since 2009 this single 25 meter dish has been a national heritage site.

Dwingeloo Radio Observatory as a SatNOGS 📡 station

Dwingleloo Satellite Antenna in the Netherlands
Dwingleloo Satellite Antenna in the Netherlands [Source: Wikipedia]

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

Element14 Video on Setting up a Portable Raspberry Pi & RTL-SDR Based NOAA Weather Satellite Receiver

Electronics distributor element14 has uploaded a video to their 'element14 presents' YouTube channel showing presenter Matt building and setting up a portable Raspberry Pi & RTL-SDR based NOAA weather satellite receiver. More information is also available on their supplemental content page.

The build consists of a Raspberry Pi, RTL-SDR and QFH antenna as the basic components. However, it is made into a very nice portable unit by using a stripped down LCD monitor placed into a heavy duty waterproof brief case. The whole thing is powered via a PC power supply. After the build is completed, Matt leaves the case on the roof for a few days collecting images.

Emboldened by the success of his Raspberry PIrate radio, Matt indulges in some more radio hacking by building a specialized QFH antenna and a briefcase form-factor satellite receiver in an attempt to intercept "faxes" from OUTER SPAACEEE!!! Connect with Matt on the element14 community: http://bit.ly/2RiSXC5

Project TIROS is a self-contained, Raspberry Pi-based satellite signal reception system designed to automatically download images and data from NOAA's POES spacecraft as they pass overhead and display the data on an integrated LCD panel. In this video, Matt will walk through how to set up an RTL-SDR module with a Raspberry Pi for automated satellite downloads as well as how to design and build a quadrifilar helical antenna for polar-orbiting signal reception.

Raspberry Pi NOAA Satellite Receiver

Designing and Testing a PCB Wideband Spiral Antenna

Back in January we posted about a Vivaldi antenna project by "hexandflex". In that project he showed how he designed and manufactured the Vivaldi. A Vivaldi antenna is wideband and directional and the design works well for frequencies above 800 MHz, but becomes too physically large to handle for lower frequencies like 400 MHz. In his latest project, hexandflex has designed a PCB based spiral antenna to cover these lower frequencies.

Hexandflex's post is split into three parts. The first post introduces us to his motivation and talks about what spiral antennas are. The second post discusses the modelling and simulation of the antenna with OpenEMS. OpenEMS is a free front end for MATLAB or Octave which allows you to simulate antenna parameters such as impedance and radiation pattern. Finally in the third post the real world parameters of the antenna are determined in an anechoic chamber owned by Antenna Test Lab, a professional antenna testing agency.

Hexandflex is currently selling his spiral antennas over on Tindie. There are two versions, one smaller one costing $32 designed for 800 MHz+ and a larger one costing $42 designed for 300 MHz+. Both come with suction cups that allow for easy window mounting.

The 800 MHz+ and 300 MHz+ spiral antennas by Hexandflex
The 800 MHz+ and 300 MHz+ spiral antennas by Hexandflex

RPiTX v2 Released: Easily Record and Replay with RTL-SDR and a Raspberry Pi

RPiTX is software for the Raspberry Pi which can turn it into a 5 kHz to 1500 MHz transmitter which can transmit any arbitrary signal. In order to transmit the software does not require any additional hardware apart from a wire plugged into a GPIO pin on the expansion header. It works by modulating the GPIO pin with square waves in such a way that the desired signal is generated. However, although additional hardware isn't required, if RPiTX is to be used in any actual application a band-pass filter is highly recommended in order to remove any harmonics which could interfere and jam other radio systems.

Earlier this month RPiTX was upgraded to version 2. One of the changes is a new GUI for testing the various transmission modes. Currently it is possible to transmit a chirp, FM with RDS, USB, SSTV, Opera, Pocsag, SSTV, Freedv. There is also a spectrum painter which allows you to display an image on a SDR's waterfall.

The RPiTX V2 GUI
The RPiTX V2 GUI
Painting an Image on a SDR Waterfall Display with RPiTX v2
Painting an Image on a SDR Waterfall Display with RPiTX v2

The RPiTX v2 update also makes recording a signal with an RTL-SDR, and replaying that signal with RPiTX significantly easier. Previously it was necessary to go through a bunch of preprocessing steps (as described in our previous tutorial) in order to get a transmittable file, but now RPiTX is capable of transmitting a recorded IQ file directly. This makes copying things like 433 MHz ISM band remotes significantly easier. One application might be to use RPiTX as an internet connected home automation tool which could control all your wireless devices.

Finally, another application of the RPiTX and RTL-SDR combination is a live RF relay. The software is able to receive a signal at one frequency from the RTL-SDR, and then re-transmit it at another frequency in real time. Additionally, it is also capable of live transmodulation, where it receives an FM radio station, demodulates and then remodulates it as SSB to transmit on another frequency.

The RPiTX V2 RTL-SDR Menu
The RPiTX V2 RTL-SDR Menu
RPiTX v2 re-transmitting a broadcast FM signal live at 434 MHz.
RPiTX v2 re-transmitting a broadcast FM signal live at 434 MHz.

Constructing a 3D Printed Wideband 900 MHz to 11 GHz Antenna

Thanks to Professor John Jackson of JR Magnetics for writing in and sharing his design for a 3D printed wideband antenna designed for 50 Ohm 900 MHz to 11 GHz operation.

John required a wideband antenna that could cover the cellphone bands, WiFi, Bluetooth up to 6 GHz and the new USB band from 5 GHz to 10 GHz all in a single antenna installation. He also needed the impedance to be as flat as possible to reduce signal pulse distortion. First he looked into classic discone and sphere antenna designs, but found that while a sphere had the required bandwidth, it did not have the desired impedance characteristics, and a discone had the desired impedance characteristics, but not the ultra wide bandwidth required.

To get around this John combines the sphere and discone designs together to create a sort of icecream with cone looking shape. This results in the ultra wide bandwidth required, and a relatively flat SWR that stays below 2.

The design is easily reproducible by anyone with a metal 3D printer. The antenna's top hemisphere and cone are printed in brass, whilst the radome and supporting structure are printed in plastic.

We have uploaded John's original document here (pdf warning), and display some of the images below. The full build instructions can be found on his website, and John is also selling the 3D printed parts via Shapeways.

jran900-top
jran900-bottom
jran900-radome
JRAN900-mount
jran900-swr
sphere-cone-ant-geo
jran-proto-bw-175

A Step by Step Tutorial to Receiving GOES-16 Images with an RTL-SDR, Raspberry Pi and Goestools

Aleksey Smolenchuk (lxe) has recently uploaded a step-by-step guide to setting up a GOES weather satellite receiver with an RTL-SDR dongle, Raspberry Pi and the goestools software.  GOES 15/16/17 are geosynchronous weather satellites that beam high resolution weather  images and data. In particular they send beautiful 'full disk' images which show one side of the entire earth. Compared to the more familiar and easier to receive low earth orbit satellites such as NOAA APT and Meteor M2 LRPT, the geosynchronous GOES satellites require slightly more effort as you need to set up a dish antenna, use a special LNA, and install Linux software.

Aleksey's tutorial first shows where to purchase the required hardware and notes that the total cost of the system is around $185. Next he goes on to show the hardware connection order, and then how to install and configure the goestools decoding software onto a Raspberry Pi.

Aleksey's RTL-SDR Based GOES Receiver setup
Aleksey's RTL-SDR Based GOES Receiver setup

Measuring the SWR of FPV Antennas with an RTL-SDR

FPV stands for 'First Person View', and is a term used to describe the hobby of flying remote controlled aircraft entirely via the view from a wireless camera that transmits live video to the pilots screen or video goggles.

Part of the FPV hobby is to not only enjoy flying, but also to tweak the wireless video equipment for maximum range and reliability. This involves measuring the SWR characteristics of FPV antennas. SWR is a metric that describes how well the impedance of an antenna is matched with the receiver at a certain frequency. Poor SWR results in additional signal loss on top of cable and connector loss. We note that SWR is only one antenna metric, and doesn't take into account radiation pattern and antenna gain which is often more important, but it is the easiest metric to measure and control, and should give you some idea as to if an antenna was designed and tuned properly.

As FPV hobbyists are often not hams or radio professionals, most don't have access to the equipment required to measure SWR. So over on his YouTube channel bonafidepirate shows how he's been using a cheap RTL-SDR, noise source and RF Bridge to measure the SWR of his FPV antennas. The process is similar to the one shown in our tutorial, but he uses the Spektrum software which allows you to measure SWR entirely within the software itself.

In the video bonafidepirate goes over the required hardware, software and the setup, and then demonstrates several SWR scans of different FPV antennas.

DIY VSWR Meter for FPV, Lets test some antennas!