Category: Airspy

RTL-SDR.COM GOES 16/17 and GK-2A Weather Satellite Reception Comprehensive Tutorial

GOES 16/17 and GK-2A are geosynchronous weather satellites that transmit high resolution weather images and data. In particular they are far enough away from the earth to be able to take beautiful 'full disk' images which show the entirety of one side of the Earth. As these satellites are in a geosynchronous orbit, they can be counted on to be in the same position in the sky at all times, so no tracking hardware is required and images can be pulled down constantly throughout the day without having to wait for a polar orbiting satellite to pass over like you would with the NOAA APT or Russian Meteor satellites.

With a low cost WiFi grid dish antenna, LNA and RTL-SDR dongle, any home user within the footprint of one of these weather satellites can receive and decode live images directly from the sky. Setting up a station is overall not too difficult, but it can be a bit fiddly with a number of steps to complete. Below is our comprehensive guide. We'll show how to set up a self contained Raspberry Pi based system with goestools (free), as well as a guide for the Windows PC software XRIT decoder (US$125).

We've attempted to make the tutorial as newbie friendly as possible, but we do need to assume basic RF knowledge (know what antennas, SDRs, coaxial, adapters etc are), basic Linux competency for the goestools tutorial (using the terminal, using nano text editor), and basic Windows competency for the XRIT decoder tutorial (unzipping, editing text files, running programs).

Click for the full size image (14MB)
A full disk false color image received directly from the GOES-17 satellite with an RTL-SDR. Click for the full size image (14MB).

There are two fourth generation NOAA GOES satellites that are currently active, GOES-16 and GOES-17. These transmit HRIT signals, and also transmit shared data from the older third generation GOES 15, and Japanese Himiwari8 satellites. At the moment GOES-16 and GOES-17 are producing full disk images every 30 minutes, and close up "mesoscale" shots of the USA every ~15 minutes. GOES-16 (aka GOES-R) and GOES-17 (aka GOES-S) are also known as GOES-EAST and GOES-WEST respectively. At least one of these satellites can be received from North/South America, Canada, Alaska/Hawaii, New Zealand, Eastern Australia and some pacific islands.

There is also the older generation GOES-15 and GOES-14 which have been placed in standby orbits. These transmit LRIT signals which provide images at a slower rate. 

GOES 16/East and GOES 17/West Signal Footprint
GOES 16/East and GOES 17/West Signal Footprint

There is also the Korean GK-2A (GEO-KOMPSAT-2A) satellite which is very similar to the GOES satellites. GK-2A covers countries like India, Asia, Australia, New Zealand and parts of Russia. Note that you may have previously heard of the COMS-1 satellite which used to cover this area. Since July 2019 COMS-1 was replaced by GK-2A. Unlike GOES, GK-2A images are encrypted. However it has been found that "sample" encryption keys found online in demo code work just fine.

GK-2A contains both LRIT and HRIT channels, but at the moment only the LRIT channel can be decoded with the currently available software. The LRIT channel sends full disk IR images every 10 minutes in 2200 x 2200 resolution. Compared to the 5424 x 5424 resolution GOES full disk images, this is smaller, but still large enough to be interesting.

Note that even if HRIT decoding is added by the current software, you would require an Airspy or other wideband SDR as the GK-2A HRIT signal bandwidth is 5 MHz. Also since the HRIT bandwidth is so wide, the signal strength is reduced, meaning that you'll need a larger dish. People who have received the HRIT signal note that a 3M+ sized dish seems to be required.

GK-21 (GEO-KOMPSAT-2A) Foorprint
GK-21 (GEO-KOMPSAT-2A) Footprint

You might ask why bother receiving these satellite images directly, when you can get the exact same images from NOAA at https://www.star.nesdis.noaa.gov/GOES/index.php. Well, you might want to set up your own station to be independent from the internet, or you live in a remote location without internet, or maybe just for the fun and learning of it.

To set up a receiver for GOES 16/17 HRIT or GK-2A LRIT you'll need to purchase a dish antenna such as a cheap 2.4 GHz WiFi antenna, an RTL-SDR, GOES LNA, and a Raspberry Pi if using goestools, otherwise a Windows PC can be used. The total cost could be anywhere from $150 - $200 depending on what pieces you already have available.

Before we start the tutorial, you might want to use an augmented reality Android app like "Satellite-AR" to get a rough idea of where either GOES 16/17 or GK-2A (GEO-KOMPSAT-2A) is in your sky, and if receiving them is even feasible for your location. You'll need to find an area on your land where you can mount a small satellite dish with an unobstructed line of sight view to the satellite (no trees or buildings can be blocking the signal path). If the satellite is low on the horizon (below 25 deg elevation), then things get a little more difficult as you have more obstructions and a weaker signal. But it can still be done, and we're able to routinely get good results at 24.5 deg elevation.

Note that for Europe and Africa, unfortunately there are no satellites that can be received easily with an SDR and LNA. But you might instead be interested in the EUMETCAST service, which can be received from EUTELSAT 10A (Ku band), Eutelsat 5 WEST A (C Band) and SES-6 (C Band) . To receive this service you'll need a DVB-S2 receiver and a satellite dish with appropriate band LNB. You also need a license keys and software which all together cost €100. EUMETCAST reception is not covered in this tutorial, instead see this video.

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Decoding PAL Video from a Nintendo with an Airspy SDR

Oona (also known as [Windytan] and @windyoona) was recently looking for a way to capture PAL composite video from her old 1980’s Nintendo Entertainment System (NES) without spending a bunch of money on what are often poor video capture cards. As she already owned an Airspy SDR she decided to receive the PAL signal with the Airspy and modify some software to act as a PAL decoder.

PAL decoding was handled via some modifications to her private Tempest software. Normally Tempest type programs like TempestSDR that we covered in a [previous article] are used to spy on computer/TV monitors from signals that are unintentionally emitted in the surrounding area.

Oona has made the connection from the composite output directly to the SDR antenna input so it’s not unexpected that you’d have a strong signal. However, I have to admit that’s an incredibly clear image for a video being demodulated via a software radio.

What makes this an even more amazing feat is that the latency is low enough that it’s nearly playable using a computer and SDR in place of a television set.

We note that we’ve also seen SDRs used to decode standard PAL TV broadcasts before with an SDR# plugin called TVSharp.

Using an Airspy HF+ Discovery to Hunt for HF Beacons

Over on YouTube Tech Minds has posted a video of him using an Airspy HF+ Discovery to hunt for signals like non-direction beacons (NDB's) and other morse code CW beacons. The Airspy HF+ Discovery is a new software defined radio that builds upon the already excellent original Airspy HF+.

One key improvement that many people have been experimenting with is it's improved VLF and LF capabilities, which is where most beacons are. It is capable of tuning down to 0.5 kHz (500 Hz). Over on Twitter, @prog (creator of these Airspy products) has been experimenting with simple and small ferrite loop antennas for VLF/LF and finding excellent results due to the low noise figure and good impedance matching of the HF+ Discovery.

Hunting HF Beacons With An Airspy HF+ Discovery

SDRTrunk 0.4.0 Alpha 9 Updates Highlighted

You may recall that a few years ago we released a tutorial on how to set up and use [SDRTrunk]. Fast forward a few years and the software has seen numerous changes. This application was designed primarily for tracking trunking radio systems but also has the ability to decode things like MDC-1200, LoJack and more.

The software is compatible with many Software Defined Radios such as our RTL-SDR v3, HackRF and the Airspy. Some of the newer improvements include a bundled copy of java so that an installation of java is not required on the host computer, as well as decoding improvements for P25 among other digital voice modes. You can find a full list of improvements along with the latest release on [GitHub]

The biggest feature many have been waiting for is the ability to import talk groups for their radio system into the application from radio reference. While this has not yet been implemented, user [Twilliamson3] has created a [web application] that will convert table data from radio reference into a format that is supported by SDRTrunk.

SDRTrunk Screenshot
SDRTrunk Screenshot

Fenu Radio Reviews the Airspy HF+ Discovery

The Airspy HF+ Discovery is a smaller, lighter and improved version of the Airspy HF+ which is an HF and VHF SDR with very high dynamic range. The Discovery builds on the HF+ by adding low loss preselectors. This increases the dynamic range even further, and allows the Discovery to compete with some very high end (and much more expensive) SDRs.

Currently the Airspy HF+ Discovery is available for preorder for USD$169. There have been a few delays in getting the unit out, but it appears that the Airspy team will begin shipping very soon.

Over on his blog, radio product reviewer Fenu-Radio has received an Airspy HF+ Discovery, and has given it an in depth review and put it through several real world tests. Fenu-Radio notes that while the initial prototype unit that he received had some issues with overload above 19 MHz, the latest production version has completely remedied this, resulting in impressive performance that competes favorably with the high end USD$2000 Winradio G33DDC software defined radio.

In the review Fenu-Radio compares the Discovery against the G33DDC and finds absolutely no difference in performance between the two. In the review he's also uploaded several audio comparison samples so that you can hear for yourself how identical the two radios are.

Fenu-Radio's Airspy HF+ Discovery Review Unit
Fenu-Radio's Airspy HF+ Discovery Review Unit

A Low Cost 2.4 GHz Downconverter from off the Shelf Dev Boards

Over on GitHub Ian Wraith has released his design and microcontroller code for a low cost 2.4 GHz downconverter circuit. A downconverter is a hardware device that shifts the signals that it receives into a lower frequency band. This is useful in the case of RTL-SDRs and Airspy SDRs, as their maximum frequency range is only 1.7 GHz. Ian's 2.4 GHz downconverter reduces those 2.4 GHz signals down to 1 GHz, which can then be received with his Airspy.

Rather than designing a circuit from scratch, Ian's design makes use of several very cheap Chinese evaluation/development boards that he found on eBay. It costs of a mixer board, oscillator board, and an STM32 development board for controlling the oscillator board via SPI. The whole set of hardware cost him less than £30 (~37 USD).

After spending some time working through the difficulties in programming the SPI interface on the STM32 board, he was able to get the downconverter circuit fully working. He notes that he's been able to receive WiFi, Zigbee, Bluetooth and ISM band signals at 2.4 GHz, as well as 3G and 4G cellular signals at 2.6 GHz.

Ian Wraith's Downconverter consisting of three off the shelf cheap Chinese eBay boards.
Ian Wraith's Downconverter consisting of three off the shelf cheap Chinese eBay boards.

SignalsEverywhere: Common Modulations Tutorial Video

This week on the SignalsEverywhere YouTube channel, host Corrosive gives us a tutorial on common modulations that you'll see on your software defined radio. His tutorial covers Amplitude Modulation (AM), Frequency Modulation (FM), Single Side Band (SSB) and Conintuous Wave (CW) modulations. In the video he shows what they look like and how to select the correct mode and bandwidth settings in SDR#. Corrosive uses an Airspy in the video, but the same concepts are valid for any SDR, like the RTL-SDR.

If you're new to SDR then this is a great introductory video to watch and learn from.

AM FM SSB and CW | Common Modulation You'll See on SDR

SignalsEverywhere: What SDR To Buy? Choose the Right one For You

Over on his YouTube channel SignalsEverywhere, Corrosive has just released a new video titled "Software Defined Radio Introduction | What SDR To Buy? | Choose the Right one For You". The video is an introduction to low cost software defined radios and could be useful if you're wondering which SDR you should purchase.

The video includes a brief overview of the Airspy, KerberosSDR, PlutoSDR, LimeSDR Mini, HackRF, SDRplay RSPduo and various RTL-SDR dongles. In addition to the hardware itself Corrosive also discusses the compatible software available for each SDR.

Software Defined Radio Introduction | What SDR To Buy? | Choose the Right one For You