Tagged: sdrplay

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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SDRplay RSPDuo Diversity: Combing a Magnetic Loop and Miniwhip Antenna

The SDRplay team have posted some more videos that demonstrate the SDRplay Duo's diversity function. The SDRplay RSPDuo is a 14-bit dual tuner software defined radio capable of tuning between 1 kHz - 2 GHz. It's defining feature is that it has two receivers in one radio, which allows us to combine the signal from two antenna together.

In the video Jon uses a Wellbrook Magnetic Loop antenna and a Bonito Miniwhip antenna both connected to the RSP Duo. Individually each antenna receives the signal relatively poorly and fades in and out as conditions and signal reflections fluctuate. However, with diversity enabled the SNR is improved and fading is significantly reduced.

The method they use to combine signals is a relatively simple method called maximum-ratio combining (MRC). The idea is that the two signal channels are added together, with the currently stronger and less noisy channel having increased gain. So while the signal levels fluctuate, as long as one antenna can receive the signal you will see no fading.

SDRplay HF Diversity Demo

SDRplay note that the key to a good setup is to have the antennas spaced out at a quarter wavelength of the signal frequency that you are receiving. In a second video they show how to properly set up an antenna system for proper HF diversity receiving.

This video demonstrates how SDRuno diversity and the RSPduo can bring enhanced reception at HF using 2 antennas separated by approximately a quarter wavelength. It uses the the current version of SDRuno (V 1.32) and the dual tuner RSPduo SDR from SDRplay.

In this experiment we had a wire dipole with one leg approximately a quarter wavelength from a Boniwhip vertical - both were picking up similar strength signals before going into "diversity" (max ratio combination) mode.

The benefits of diversity tuning at HF are very dependent on many variables, most notably the changing nature of the reflected signal path and the degree to which noise and unwanted signals are not as coherent as the wanted signal.

Antenna and SDRplay set-up for HF diversity reception (rev1)

A Demonstration of RSPDuo Diversity Being used to Cancel Local Interference

SDRPlay have recently published a video demonstrating how the new RSPduo diversity feature in SDRUno can be used to cancel local interference.  The SDRplay RSPDuo is a 14-bit dual tuner software defined radio capable of tuning between 1 kHz - 2 GHz. It's defining feature is that it has two receivers in one radio, which should allow for interesting phase coherent applications such as diversity. The RSPDuo's diversity feature allows us to either combine two antenna signals together for an up to 3 dB increase, or for removal of an unwanted noise source via subtraction of signals.

In the video they show a broadcast AM signal that has it's SNR reduced by being on top of a local electrical noise source. The use a Bonito Mega-dipole on tuner 1, and a Bonito Mini-whip on tuner 2. The Mini-whip appears to receive the local interference stronger, so can be subtracted away from the Mega-dipole's signal with the diversity function. The result is improved SNR, and the noise is almost entirely cancelled.

There are 2 very practical applications for diversity software. The first is MRC (Maximum Ratio Combination) Diversity which, in order to be effective, needs two antennas presenting the same signal with some degree of diversity. Then there is this second impressive application which is becoming more and more useful due to the growing number of domestic sources of interference.

This is possible in an RSPduo, due to the coherent nature of the combined tuner streams being presented to the computer for processing.

Using Diversity in SDRplay's SDRuno to Cancel Local Interference

Two Antenna Diversity For the SDRPlay RSPDuo now Available in SDRUno

The SDRplay RSPDuo is a 14-bit dual tuner software defined radio capable of tuning between 1 kHz - 2 GHz. It's defining feature is that it has two receivers in one radio, which should allow for interesting phase coherent applications such as diversity.

In the latest v1.32 release of SDRUno a diversity feature has been added. Diversity reception was demo'd back in May at Hamvention, and we have a previous post with video about that. Diversity works by subtracting or adding two signals from the two receivers running independent antennas. The result is an up to 3 dB increase in SNR, and better performance with fading signals. They write:

From V1.32 onwards, MRC (Maximal Ratio Combining) Diversity is supported using the RSPduo. MRC Diversity can be used to combine the 2 tuner input streams together to potentially improved the SNR (signal to noise ratio). The same frequency is used for both tuners in the RSPduo and the gain can be adjusted either on each tuner independently or locked together (the default method).

Diversity mode is enabled by clicking on the RSPduo MODE dropdown and select DIVERSITY. Make sure both the 50 ohm ports are connected to the correct input source and note that the HiZ port is not available for Diversity mode. Trying to use the HiZ port will result in an error message being displayed.

Diversity Controls in SDRUno
Diversity Controls in SDRUno

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

SDRPlay Hamvention Demo of SDRUno and RSPDuo Diversity Features

At this years Hamvention Chris Howard from ICQ Amateur interviewed Andy at the SDRplay booth. In the interview they discuss various new features and improvements to SDRuno, the official software for SDRplay devices.

Later they also discuss the RSPduo, and the new diversity feature coming in a new version of SDRUno that is due to be released in a few weeks. The diversity feature works with the two tuners on the RSPduo to combine or subtract signals from two different antennas. Andy notes that diversity should be able to achieve a net 3dB increase in SNR, and is most useful for a moving or dynamic signal environment.

Finally Andy discusses the future development of SDRUno and notes that they're working on a plugin environment which will allow the creation of third party demod/decoders, a multiplatform server for remote SDR, and eventually cross platform drivers and SDRUno.

SDRPlay Announce Update to SDRUno and Future Plans for Software Defined Radio at Hamvention 2019

SDRplay Spectrum Analyzer Software Updated to V1.0a

Steve Andrew, the author of the SDRplay Spectrum Analyzer software has recently released an update which enables several new features. This software allows you to use SDRplay SDRs to scan a wide swath of bandwidth by rapidly scanning in 10 MHz (or less) chunks over the SDRplay's frequency range. The SDRplay team write:

We are pleased to announce the availability of V1.0a of the Spectrum Analyser software developed by Steve Andrew specifically for the RSP line of products. This is a very-much upgraded version of the original alpha release and includes many new features as well as removing the limitations imposed on the previous version. New features include multiple traces, a versatile marker system with maths, peak find and display functions, Zero or non-Zero IF options and an upgraded tracking generator system. Currently support are: 

RSP1
RSP2/RSP2pro
RSP1A
RSPduo (single tuner mode)

SDRplay Spectrum Analyzer
SDRplay Spectrum Analyzer

Building a Transmit/Receive Relay System for a “Boat Anchor” Transmitter and SDRplay

Over on YouTube user ElPaso TubeAmps has uploaded a video showing his transit/receiver relay system that allows a "boat anchor" (old radio) ham radio transmitter and SDRplay SDR receiver to coexist. In order to protect the SDRplay's front end from being destroyed by a ham radio transmitting on the same antenna, a relay should be used to ground the SDRplay during a ham radio transmission. He writes:

How to build a small chassis and relay system to switch the antenna from the SDR input to ground and open the speaker connection from the PC to the speakers during transmit. I use "boat anchor", i.e. separate VFO for transmitter and receiver equipment and this video is about that type of connection and is not for transceivers.

SDRPlay, RTL-SDR, Transmit-Receive , PC Speaker, T/R Switch