Category: Antennas

Creating an Inmarsat STC-C EGC Live Stream with an RTL-SDR, Raspberry Pi and OpenWebRX

Thanks to Zoltan (aka Veryokay on YouTube) for submitting information about his Inmarsat STD-C EGC live stream setup. His setup allows him to access the Inmarsat STD-C signal from anywhere in the world over the internet, thanks to the use of an OpenWebRX server. Inmarsat STD-C is a geostationary satellite service that provides information for search and rescue, as well as news, weather and incident reports for mariners. We have a tutorial from a few years ago which shows some example messages. OpenWebRX is an efficient SDR streaming server platform that allows you to access RTL-SDR's and other SDRs from anywhere in the world via an internet connection.

In his setup Zoltan uses a Raspberry Pi 3, RTL-SDR Blog V3, L-band LNA and L-band antenna for receiving and processing the signal. Power is provided via a Power over Ethernet (PoE) adapter, and the whole thing is placed outside, in a weatherproof plastic lunchbox.

The video shows the hardware, and then goes on to describe the software setup, along with a demonstration of the OpenWebRX stream. More information as well as the link to his publicly accessible OpenWebRX Inamrsat STD-C stream can be found on his blog post.

INMARSAT STD-C EGC live streaming

Weatherproofing the RTL-SDR Blog Multipurpose Dipole Antenna

Thank you to YouTube user "ModernHam" for submitting his video that shows one way to weatherproof our 'RTL-SDR Blog Multipurpose Dipole Antenna'. This is the antenna we include as part of our RTL-SDR kit, and it is an excellent beginners antenna. Dipole antennas typically receive better than mag-whips, are easier to mount on windows, and can receive 137 MHz weather satellites too.

However, due to their portable telescopic collapsible design, our antennas are not designed for permanent outdoor use as dirt and grime can gum up the collapsing mechanism. In his video ModernHam decided to waterproof the dipole for permanent outdoor mounting. To do this he modified the plastic base by cutting it down, and then places the dipole inside a PVC pipe with some bubblewrap used to hold it in place. This keeps the elements out, and looks pretty good mounted up high too.

Weatherproofing a RTL-SDR Stock Dipole Antenna

Building a Carbon Fibre Dual Band Yagi Antenna for Amateur Radio Satellites with 3D Printed Parts for 20€

Back in early 2017 we posted about Manuel's (aka DO5TY / Tysonpower) design for a single band 140 MHz 3D printed carbon fibre Yagi antenna. Today he's submitted a new video about creating a dual band 3D printed carbon fibre cross Yagi antenna for only 20€. Note that the video is narrated in German, but there are English subtitles. He's also uploaded an English text tutorial to his blog, which includes links to the 3D printer STL files.

The antenna is designed to be a low cost replacement for the commonly used Arrow dual band 2m/70cm antenna which is designed for receiving and transmitting to amateur radio satellites. Many amateur radio satellites have an uplink frequency set at around 145 MHz, and a downlink frequency around 435 MHz (and some satellites have the frequencies reversed). So a dual band Yagi is ideal for these satellites. Manuel writes that with his 5W Baofeng handheld he's already made several successful contacts with his new antenna.

Manuel's antenna consists of several 3D printed joints, with a carbon fibre rod used as the main boom. Aluminum rods make up the receiving and transmitting elements. The video also discusses impedance matching and how he uses a diplexor so that there is only one connection required to the radio. The advantage of his antenna over the Arrow is that it is significantly cheaper, and also much lighter in weight.

[EN subs]Carbon Arrow Yagi Antenne - leichte Dual Band Yagi für 20€ bauen

Help Track Data from CubeSail with an RTL-SDR

On December 16 Rocket Lab launched 13 new cubesats into orbit via it's Electron rocket which was launched from New Zealand. One of those Cubesats is "CubeSail" which is a set of two satellites that aims to deploy a 260 m long solar sail between the two.

CubeSail is a technology demonstration by CU Aerospace which shows the viability of solar sail propulsion for deep space missions. It was built and is operated by students at the University of Illinois at Urbana-Champaign through the Satellite Development, or SatDev student organization.

Over on Reddit, one of the engineers working on the Cubesail project has put out a request to help receive and upload any telemetry that you receive from the Cubesail satellite. Currently they only have one ground station which makes monitoring the satellite difficult as they can only collect data when it is passing overhead.  By employing the help of radio enthusiasts from around the world they hope to gather more data. He writes:

Hello amateur radio enthusiasts! I'm part of the CubeSail mission, one of the 13 satellites deployed early this morning (2018/12/16) from RocketLab's Electron rocket.

The reason why I'm posting is that we need your help! We're trying to gather as much data as possible from the beacons, but only have one groundstation at the moment. I've put together a little Python script which can be used to decode the data, so if you're interested and willing to help out a bunch of eager fellow space enthusiasts to get some data, please try and get a packet or two!


Here's the information you need to know (let me know if I'm missing anything):

Frequency: 437305 kHz

Modulation: GFSK (GR3UH scrambling)

Bandwidth: 15kHz

Callsign: WI2XVF

Link Layer: AX.25/HDLC

Baud Rate: 9600

TLE:

cubesail_temp
1 99999U          18350.31100694  .00048519  00000-0  21968-2 0 00004
2 99999 085.0351 178.2861 0013006 291.7248 120.7146 15.20874873000012

Here's a link to the decoder, it runs in Python 3: https://github.com/ijustlovemath/cubesail-decoder

According to the information a 437 MHz antenna is required, and most likely it will need to be a directional antenna that is hand or motor tracked. Some SatNOGS ground stations are already receiving and recording Cubesail data too.

An artists rendition of the CubeSail solar sail deployment
An artists rendition of the CubeSail solar sail deployment

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