Category: Antennas

SignalsEverywhere: KerberosSDR Direction Finding Video Tutorial

Over on his YouTube channel SignalsEverywhere, Corrosive has uploaded a new video about setting up a KerberosSDR for direction finding. KerberosSDR is our new 4-input Coherent RTL-SDR that was crowdfunded on Indiegogo, and has now shipped to all backers. With KerberosSDR applications like direction finding and passive radar are possible. If you're interested, there are still about 70 units available in this batch. After that a second batch will be available in a few months.

In the video he goes over the full set up procedure, from setting up his chosen computing platform (a Raspberry Pi 3) to connecting up the KerberosSDR, connecting to it's web interface, calibrating, setting up the antennas, and then demonstrating some direction finding with four whip antennas on his car and a HackRF used as a signal source.

Radio Direction Finding Equipment KerberosSDR Coherent 4 x RTL SDR RDF Setup

Testing an SDRplay RSPduo with Bonito Active Loop Antennas

Bonito is a company that sells various active dipole and loop antennas for ham radio and DX applications. Recently they decided to test their MegaLoop FX and MegaDipol MD3000DX antennas on an SDRplay RSPduo, and compare it against a higher end WinRadio. Bonito found that the RSPduo performed well on the weaker longwave stations, but the Winradio outperformed it on the stronger ones. The differences were due to the better dynamic range of the Winradio.

The article goes on to make some recommendations for using their antennas on the RSPduo. They write that if intermodulation due to very strong signals occurs, there are some fixes that can be applied on their antennas to desensitize them and prevent overload. With the loop, a smaller loop size should be used, and the gain selector should be set to medium or min. With the dipole, they note that shortening the elements, and using it in an L-configuration with the lower radiator pointing towards the interfering signals can be used to attenuate them out. This works because a dipole configured in a L shape provides a bit of directionality.

The article also notes how grounding, very good coax shielding, good quality USB cables and galvanic isolation are all very important for reducing noise.

Bonito RSPduo Antenna Test Setup
Bonito RSPduo Antenna Test Setup

Es’hail-2 Amateur Transponder Now Active

Es'Hail 2 Coverage
Es'Hail 2 Coverage from Amsat-UK

Es'hail 2 was launched last November and it is the first geostationary satellite to contain an amateur radio transponder. The satellite is positioned at 25.5°E which is over Africa. It's reception footprint covers Africa, Europe, the Middle East, India, eastern Brazil and the west half of Russia/Asia. There are two amateur transponders on the satellite. One is a narrow band linear transponder which uplinks from  2400.050 - 2400.300 MHz and downlinks from 10489.550 - 10489.800 MHz. Another is a wide band digital transponder for amateur digital TV which uplinks from 2401.500 - 2409.500 MHz and downlinks from 10491.000 - 10499.000 MHz.

Although it launched last year it takes several months for the engineers to test and qualify the transponder for use. Over the last few weeks the transponder was intermittently active during the testing, but now since Feb 13 2019 the amateur transponder has finally been fully activated for amateur radio use.

To receive it with an RTL-SDR or most other SDRs an LNB is required to receive the 10 GHz signal and downconvert it into a frequency range that most SDRs support. Typically an Octagon LNB is used, and these are easy to find and cheap as they are often used for satellite TV.

From various reports seen on Twitter, it seems that the signal is strong enough that a satellite dish is not required for receiving - simply pointing the LNB directly at the satellite is enough.

If you can't set up a receiver, there is an OpenWebRX livestream of the Es'hail 2 narrowband channel that has been set up by Zoltan/RFSparkling which is available at sniffing.ddns.net:8073 (note the server can only handle 8 users at a time, so try again later if it's busy). Also as pointed out by KD9IXX on Twitter, there are also several websdr.org servers receiving and streaming Es'hail2 including an Airspy based one run officially by AMSAT-DL.

3D Printed V-Dipole Holder for Our RTL-SDR Blog Multipurpose Dipole Kit

Over on Thingiverse user f16v1per has created a 3D printed bracket that can help with securely holding our multipurpose dipole kit at a 120 degree angle, which is the perfect angle to use when in a V-Dipole configuration. A V-Dipole is simply a dipole antenna spread at 120 degrees, placed horizontal to the ground, and typically oriented in a North-South direction for receiving weather satellites.

Back in 2017, Adam 9A4QV wrote about how a V-Dipole could be used as a very simple yet effective antenna for receiving weather satellites. Since then it has become a popular beginners choice for receiving polar orbiting satellites like NOAA and Meteor M2.

3D Printed V-Dipole Angle Spacing Bracket
3D Printed V-Dipole Angle Spacing Bracket

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