Everyday multiple NOAA weather satellites pass above you. Each NOAA weather satellite broadcasts an Automatic Picture Transmission (APT) signal, which contains a live weather image of your area. The rtl-sdr dongle combined with a good antenna, SDRSharp and a decoding program can be used to download and display these live images several times a day.
This tutorial will show you how to set up a NOAA weather satellite receiving station, which will allow you to gather several live weather satellite images each day. Most parts of this tutorial are also applicable to other software radios, such as the funcube dongle and HackRF, but the rtl-sdr is the cheapest option. Hardware radio scanners can also work, provided the radio has a large IF bandwidth (30 KHz +) and a discriminator tap.
Examples
YouTube user GaitUutLiern shows an example of receiving NOAA satellite weather images with rtl-sdr, SDRSharp, decoding program WXtoImg and a QFH antenna.
Here, YouTube user themrworf1701 shows a video tutorial on how he set up his weather satellite receive station. He used an rtl-sdr, SDRSharp, WXtoImg, a QFH antenna and also an LNA.
Requirements and Setup
To set up a NOAA weather satellite receive station you will need
A right hand circularly polarized antenna tuned to 137 MHz.
Software such as WXtoImg for decoding the APT signal.
We will assume you have the rtl-sdr dongle set up and working already. If you have not bought a dongle yet, see the Buy rtl-sdr page for information, and the check out the Quickstart Guide for an easy setup routine with SDRSharp. You will also need to have an audio piping method installed and set up. Audio piping will allow the audio from SDRSharp to be passed to a decoding program. You can use either windows stereo mix, VB-cable (free) or virtual audio cable (paid with trial version).
The sampling rate of your audio piping method should be set to at least 48000 samples/sec. To set this in Windows, right click your device in the Windows sound recording tab, go to properties and under the advanced tab, set the sample rate to 48000 Hz. Do the same to the same device under the Playback tab as well.
Also, in your SDRSharp folder, open SDRSharp.exe.Config in a text editor such as Notepad, and ensure the key minOutputSampleRate has a value of 48000 such that the line reads as <add key=”minOutputSampleRate” value=”48000″ />.
NOAA Weather Satellite Antennas
The NOAA APT weather satellites broadcast their signal at about 137 MHz, and their signals are also right hand circularly polarized (RHCP), which means you will need a right hand circularly polarized antenna to properly receive the signals. This is because as the satellites broadcast their signal, they also rotate, rotating the signal polarization. Three options for easy homemade circularly polarized antennas are presented below.
Turnstile Antenna
A turnstile antenna is a circularly polarized antenna. It can be built in two modes, normal and axial. For satellite reception we want it in axial mode.
A page showing a turnstile antenna for 137 MHz is here.
Quadrifilar Helix (QFH) Antenna
A Quadrifilar Helix (QFH) is a circularly polarized antenna that can be constructed out of PVC pipe and coax cable. Most people report that the QFH antenna has slightly superior reception compared to the turnstile.
If you are into antenna theory, a good technical paper on the QFH (called QHA in the paper) can be found here.
A tutorial on building a QFH out of coax cable and PVC pipe can be found here. Another home brew QFH antenna constructed out of copper wire is here. Also, a good calculator for determining QFH antenna dimensions for 137 MHz can be found here.
Double Cross Antenna (DCA)
Another antenna that works well with the NOAA APT satellites is the double cross antenna (DCA). It is basically four dipoles arranged in a certain way to produce circular polarization.
A good guide on DCA antennas, and constructing them can be found in this pdf guide by Gerald Martes (KD6JDJ).
Yagi antennas can also work, but since they are so directional you will need to carefully track the satellite by hand, or by using a rotor controller.
Software Tutorial
The NOAA satellites only pass overhead at certain times of the day, broadcasting a signal. These signals appear at around ~137 MHz, and only when a satellite is passing overhead. Each satellite has a different frequency. Currently only NOAA satellites 15, 18 and 19 are operational, their frequencies are shown below.
NOAA 15 – 137.6200 MHz
NOAA 18 – 137.9125 MHz
NOAA 19 – 137.1000 MHz
An example of a NOAA APT weather satellite signal is shown to the left, and an example audio file of the signal is shown below.
WXtoImg Tutorial
WXtoImg is a free weather satellite decoding program, which can decode the APT signal, and also tell you the times and frequencies of the satellites passing overhead. There is also a paid version of WXtoImg which can unlock more features, however it is not required for use with rtl-sdr. To use WXtoImg and SDRSharp together follow the instructions below.
First, download and install WXtoImg from their homepage here.
Next open WXtoImg, and then set your Ground Station Location, (which is the coordinates of your antenna) by going to Options -> Ground Station Location. The city you are in should suffice, but you can be more accurate by entering in an exact latitude and longitude if you want.
Set your audio piping method which you have chosen in WXtoImg. Go to Options -> Recording Options, and ensure the correct device is selected under the soundcard option.Also, here you can adjust the “Record only when active APT satellites are overhead” “with maximum elevation above (degrees)” and “record only when satellite is above (degrees)” settings. You may want to reduce the default values if you have an antenna with a good view of the sky, and find that WXtoImg stops recording or doesn’t start fast enough even though the APT signal is present in SDRSharp.
Now you will need to update your Kepler files. These files contain the information about satellite locations. They need to be periodically updated, because satellites drift in their orbit over time. Go to File -> Update Keplers to do this. Make sure you have an internet connection for the update.
Now you can go to File -> Satellite Pass List, and find a time when a satellite will be passing overhead. Take note of the frequency as well.
When the time comes for the satellite to appear, open WXtoImg, and then go to File->Record, and click on Auto Record. The recording and decoding will begin when the satellite appears on your horizon, and stop when it goes out of view according to the times in the satellite pass list.
Open SDRSharp select the audio piping method you are using under the Audio Output drop down box, and then tune to the frequency that the satellite will be broadcasting at. Adjust the gain settings in SDRSharp under the Configure button so that you get good reception of the signal. Set the receive mode to WFM, filter bandwidth to 34 KHz and Filter Audio set to OFF. It may also be useful to ensure Snap to Grid is unchecked.
As the rtl-sdr is not frequency accurate, and also due to the Doppler effect, the signal may not be at the exact frequency it should be at. Just adjust the frequency in SDRSharp until it is centered on the satellite signal.
Adjust the AF Gain in SDRSharp, and/or Windows volume settings so that the volume bar in the bottom right hand corner of WXtoImg shows a green color.
WXtoImg should now be decoding and showing the weather satellite image as it is received. You may need to periodically adjust the frequency to center the signal as the Doppler effect will cause it to move. But, with the rtl-sdr adjusting for the Doppler shift is not critical as the filter bandwidth can be simply set larger than 34 KHz (try 36 -40 KHz) so that it is large enough to receive the entire signal even as it as it shifts.
Once the image has been fully received, you can play with the options under the Enhancements and Projection menu in order to add false color and enhance the received image.
Orbitron Tutorial
It is not entirely necessary for these NOAA satellites, but if you want the Doppler effect to be automatically adjusted for in SDRSharp, you can use free a program called Orbitron, which with the aid of a plugin, will interface with SDRSharp.
Download and install Orbiton from their website here.
Download the SDRSharp Orbitron plugin from here. The readme file comes with installation instructions, but some of the instructions did not work for me. You can try follow their instructions, or mine below. I start from the step after installing the plugin into SDRSharp. I also found that I did not need to download the DDE driver, but you might want to anyway just to be safe.
Open Orbitron in Administrator Mode (if in Windows Vista/7/8), by right clicking it, and selecting Run as Administrator. Orbitron may open in full screen mode. Press Alt+Enter to exit full screen if you wish. You will probably also be initially presented with a TLE file update screen. You can leave all the boxes as default. Click on the update button, which is the icon with a globe and lightning bolt. Orbitron will download the new TLE files. The TLE files contain the satellite orbit information, and will need to be periodically updated every few days. Running Orbitron in Administrator mode is important, as otherwise the TLE files will not be able to be written to.
Close Orbiton. Now open Notepad in Administrator mode, by right clicking it’s shortcut in the Start Menu, and clicking on Run as Administrator.
In Notepad, go to File->Open, and browse to your Orbitron\Config folder. Orbitron is probably installed in “Program Files (x86)\Orbitron”. Open Setup.cfg.
At the bottom of the Setup.cfg text file, add these two lines. [Drivers]
SDRSharp=SDRSharp.exe
Now open Orbitron, and set your home location, by clicking the location tab on the bottom. You can select your city on the right side if you don’t know your exact longitude and latitude.
Next click on Load TLE, and load the noaa.txt file.
We are interested in NOAA satellites 15, 18 and 19, as they are the only ones working, so place a check next to those. Double clicking on a satellite name will select it and show it in the map window.
Now go to the Rotor/Radio tab, and set the Dnlink mode to FM-W, and the Driver to SDRSharp. Click the icon with two windows next to the Driver dropdown box, and make sure it is pressed in.
Open SDRSharp, press Play and then head to the Orbitron Plugin, select Enabled, set the Tracking Software to Orbitron, and then click connect. Now double clicking on a satellite name in Orbitron should set the correct Doppler corrected frequency in SDRSharp.
SDRSharp should now snap to the correct frequency, and adjust for the Doppler effect automatically. You will still need to manually set the correct filter bandwidth. Also, since the rtl-sdr is not frequency accurate, you will need to adjust the PPM correction in the SDRSharp configure box to ensure the signal is centered.
Some Tips
An LNA such as this one may improve signal reception, especially if you run a long feedline from the antenna to the dongle.
If you enjoyed this tutorial you may like our ebook available on Amazon.
The EAS is a national public warning system that requires broadcasters, cable television systems, wireless cable systems, satellite digital audio radio service (SDARS) providers, and direct broadcast satellite (DBS) providers to provide the communications capability to the President to address the American public during a national emergency. The system also may be used by state and local authorities to deliver important emergency information, such as AMBER alerts and weather information targeted to specific areas.
Reddit user rtlsdr_is_fun is working on software to automatically detect an EAS broadcast from a NOAA Weather Radio stream using an rtl-sdr (or any SDR, or even an internet stream) and then immediately play it and record it. This will allow the EAS alert to be heard up to 2 minutes faster than email/sms alerts, without the need to constantly listen to the NOAA WX Radio.
He stresses that his software is still in the very early alpha stages, but you can read about his project on his Reddit post here, which also contains a download link.
On Twitter user @uhf_satcom has been using a HackRF software defined radio together with GNU Radio, a tracking L-Band antenna and this HRPT decoding software to receive and decode HRPT weather satellite images. He used GNU Radio to output to a .RAW16 file, which the HRPT decoding software was then able to use to produce an image.
Finally! HRPT via SDR; http://t.co/MvLWcByZfB – hackRF + GNUradio + tracking L-Band antenna, and HRPT decoder tool = great images
HRPT is a picture transmission protocol which stands for High Resolution Picture Transmission. There are multiple satellites which broadcast weather images in this format including the NOAA, GOES, Metop-A and Feng Yun satellites. These satellites transmit HRPT at about 1.7 GHz.
Over on the SDR for mariners blog, author Akos has written two new beginners posts on getting up and running with receiving and decoding NOAA weather satellite APT images.
There are now dozens of software defined radio packages that support the ultra cheap RTL-SDR. On this page we will attempt to list, categorize and provide a brief overview of each software program. We categorize the programs into general purpose software, single purpose software, research software and software compatible with audio piping.
If you know of a program that is missing please leave a comment in the comments section at the bottom of the page.
SDR# (pronounced “SDR Sharp”) is the most popular free RTL-SDR compatible software in use at the moment. It is relatively simple to use compared to other SDR software and has a simple set up procedure. We have a full overview of the installation procedure on our Quick Start Page.
SDR# is a simple to use program that also has some advanced features. It has a useful modular plugin type architecture, and many plugins have already been developed by third party developers. The basic SDR# download without any third party plugins includes a standard FFT display and waterfall, a frequency manager, recording plugin and a digital noise reduction plugin. SDR# also decodes RDS signals from broadcast FM.
HDSDR is based on the old WinRAD SDR program. HDSDR supports the RTL-SDR through use of an ExtIO.dll module. To install HDSDR, download the program from the link on the main HDSDR page, then to use the RTL-SDR you will need to download the ExtIO_RTL2832.dll file an place it into the HDSDR folder. When opening HDSDR, select the newly copied ExtIO_RTL2832.dll. The other dlls that come with HDSDR will not work with the RTL-SDR, even though they have RTL-SDR in their filename. The official installation instructions can be found here.
Along with a FFT display and waterfall, HDSDR has some extra advanced features. Users will also find an Audio FFT and waterfall display on the bottom of the screen. The output audio can also be bandpass filtered by dragging the filter borders on the display. Bandpass filtering the audio can really help clean up a noisy signal. The audio processing also supports placing of notch filters either manually or automatically. There are also noise reduction and noise blanker features and an automatic frequency centering algorithm which will automatically center the signal, so you don’t need to click exactly in the center of a signal. Traditional ham radio users will also enjoy the S-units signal strength meter and the built in frequency manager.
SDR-RADIO.COM V2 is a popular SDR program with many advanced features. As such is it a fair amount more difficult to learn and use compared to SDR# and HDSDR. Be sure you install version 2 and not V1.5 as only V2 has RTL-SDR support.
Once sdr-radio is installed, to get it working with the RTL-SDR you will need to compile or download three .dll files (SDRSourceRTL2832U.dll, rtlsdr.dll and libusb-1.0.dll) and place them into the sdr-radio folder. To compile your own dlls see the instructions here, otherwise download the dlls directly from the bottom of this link. If the dlls were placed in the correct folder you will be able to add your RTL-SDR as a receiver by clicking on the +Definitions button, and then finding and adding the RTL SDR (USB) option under the search drop down menu.
Like HDSDR, not only does sdr-radio have a RF FFT signal and waterfall display, but also an optional audio spectrum FFT and waterfall display. Built in are also several DSP features like a noise blanker, noise reduction filter, notch filter and squelch options. The EMNS noise reduction filter is particularly good at automatically cleaning up and clarifying voice signals.
To add to the feature list, sdr-radio also has built in PSK, RTTY and RDS decoders, and also comes with a satellite tracker. Furthermore, sdr-radio has an excellent remote server which will allow you to easily set up and connect to a remote RTL-SDR server over a network or the internet. Finally, sdr-radio is capable of listening to up to 6 signals in the same chunk of visible spectrum at a time.
Linrad is a free advanced SDR program with a steeper learning curve compared to most other SDR programs. Many users prefer to use Linrad as it can be set up to have a very high amount of information density on the screen and it also has an advantage with receiving signals with the E4000 tuner as it can be made it run in a special linearity mode which significantly improves the dynamic range.
Linrad also has some very advanced features not found in most other SDR receivers. It has multi-frequency interval I/Q correction, a very powerful “smart” noise blanker, multicast output, weak signal optimized waterfall, settings to aid in taking performance measurements, two RF channel input, superior AGC and an adaptable automatic frequency controller (AFC). Linrad is probably the software most superior in terms of actual signal processing performance.
To install Linrad on Windows first download and run the setup-dll installer, and then download and extract the actual Linrad program. You will need to go through a text based set up at the very beginning.
GQRX is a free simple to use SDR receiver which runs on Linux and Mac systems. It is similar to SDR# in terms of features and simplicity of use. GQRX comes with a standard FFT spectrum and waterfall display and a number of common filter settings.
Studio1 is a non-free commercial SDR receiver with advanced DSP capabilities, and is claimed to have the lowest CPU usage of any general purpose SDR software. Studio1 supports the RTL-SDR through use of an ExtIO.dll module.
Studio1’s main selling point is that it claims that its spur/alias free dynamic range is greater than 130 dB compared to the 70 dB that most free SDR software programs have (spurious free dynamic range influences the capability of the receiver to resolve small signals in presence of in-band strong signals). It also claims that it has a very efficient DSP engine that can run well on older Pentium 4 machines.
ShinySDR is an SDR application built in GNU Radio with a web based interface. It is currently in a usable state, but is still undergoing major development. Since ShinySDR is controlled via a web interface it can easily be controlled over a network or the internet. It also has a plugin type development feature which allows demodulators to be easily written and integrated.
The current main technical advantage to ShinySDR is that it has a persistent waterfall, meaning that the waterfall can be moved, zoomed and re-tuned without loss of any history like in other SDR software.
WebRadio is a Linux based application that is attempting to build an open source system for the RTL-SDR and other software defined radios similar to the closed source WebSDR . The WebSDR system allows for multiple public users to connect to a radio over the internet and tune to various frequencies. WebRadio is currently functional but still under development.
Sodira is a Windows application that is capable of decoding AM and FM+RDS radio as well as DRM/DRM+ and time signals DCF77/HBG. It supports the use of the RTL-SDR through use of the ExtIO_RTL2832.dll module. The same ExtIO_RTL2832.dll module that is used with HDSDR and whose download is linked to in this HDSDR tutorial can be used with Sodira. Just place the dll in the same folder as Sodira, and then under Configuration->Receiver select the dll file and then click on HW Init + Start to activate the RTL-SDR.
SDRTouch was the first Android based RTL-SDR software receiver available. There is a free restricted trial version and the full version can be bought from the Google Play store. To run SDR Touch you need a modern Android 4.0+ device with decent processing power and USB OTG support. You will also need a USB OTG cable to connect to the Android device to an RTL-SDR dongle.
SDR Touch has several standard features such as FFT spectrum and waterfall displays, WFM/FM/AM/SSB tuning and a frequency manager.
Wavesink Plus is another Android based RTL-SDR receiver with a free trial and paid full version. Wavesinks main feature is that it is capable of decoding DAB+ and DRM+ digital radio signals. As well as the digital radio signals, it can also receive standard FM and do FM-RDS decoding as well. To use Wavesink, like SDR Touch you will need a decently powerful Android 4.0+ device with USB OTG cable.
An SDR receiver intended for use with the HPSDR project SDR hardware, but can be used with the RTL-SDR through use of the RTL_HPSDR translation server program. One advantage to cuSDR is that it can support up to seven simultaneous RTL-SDR dongles. cuSDR is still currently under development.
PowerSDR is an SDR receiver intended for use with the FlexRadio SDR hardware. It is compatible with the RTL-SDR through use of the RTL_HPSDR translation server program. PowerSDR is capable of supporting up to four simultaneous RTL-SDR dongles.
QtRadio is an open source SDR receiver that is based on a client-server architecture from the ground up. It is designed so that multiple clients can connect to a single server. QtRadio comes with a special RTL-SDR server which you will need to download and run.
SeeDer is a general purpose SDR GUI that has a focus on decoding data from satellites. Legality Note: SeeDeR may be an illegal clone of SDR#. If this is proven in the future we will remove links to SeeDeR on our site.
Single Purpose RTL-SDR Software
Here we list single purpose RTL-SDR supported software. By single purpose we mean an application that decodes a single protocol, or performs a single function.
RTL_FM is a command line based FM receiver for the RTL-SDR which is bundled in the official RTL-SDR release. It is extremely useful in Linux as it can be used to pipe decoded FM audio to decoder software.
SoftFM is a command line FM receiver for the RTL-SDR that is similar to RTL_FM. The difference is that SoftFM claims to get much better audio results compared to RTL_FM.
RTL_TCP is used to stream IQ data from the RTL-SDR over a TCP network. Many programs can connect to this, for example in SDR# there is the RTL-SDR/TCP option.
A Python program based on rtl_fm that allows you to tune to any station using a web interface.
RTLSDR Scanner(Windows/Linux/Mac) (Free) – Wideband Frequency Scanner
RTLSDR Scanner
RTLSDR Scanner is a simple cross platform python based wideband spectrum analyzer for the RTL-SDR. It can scan an arbitrarily large frequency bandwidth. The scanner also has an auto calibration feature which can help find the PPM offset of a dongle. Newer versions also have a GPS feature, which allows you to interface a hardware GPS receiver to the software and do signal mapping experiments.
Similar to the RTLSDR scanner but written in the basic for gambas programming language. Essentially a front end for rtl_power.
RTL Panorama (Windows) (Free) – Wideband Frequency Scanner
RTL Panorama
Another wideband RTL-SDR scanner but based on the command line software rtl_power. Essentially a GUI interface for rtl_power. Scans much faster compared to RTLSDR Scanner.
SDR-J is a free program that is split into two different programs. There is the SDR-J DAB/DAB+ receiver program and the SDR-J FM decoder program. The DAB decoder is the most popular of the two. To install the SDR-J DAB receiver go to the SDR-J website and download the dabstick-radio.zip file, unzip it and run dabreceiver.exe. If your RTL-SDR is plugged in you’ll be able to click the start button and begin choosing the DAB band in your country using the left drop down box.
ADSB# is a Windows Mode S ADS-B decoder for the RTL-SDR written by the author of SDR#. Use this program to broadcast data via TCP/IP locally via TCP to a graphical radar program such as Virtual Radar Server, Planeplotter or adsbSCOPE.
RTL1090 is another Windows Mode S ADS-B decoder for the RTL-SDR. As with ADSB# you need to use this program to broadcast data via TCP/IP to a graphical radar program. The latest installation program known as the RTL1090 IMU simplifies the installation by automatically downloading some required .dll files. The current series 2 beta version aims to improve decoding and also has a built in radar display.
Dump1090 is a lightweight command line Windows and Linux based Mode S ADS-B decoder. It also has a built in web service which can display the decoded aircraft positions on Google maps. Many people report that dump1090 has the best decoding performance.
A multiplatform command line based ADS-B Mode S and Mode A/C decoder for the RTL-SDR. Can feed Basestation natively without the need for com port converters. Can also decode Mode S and mode A/C simultaneously.
ADS-B on USB SDR RTL is an Android app that can help receive, decode and display on a map ADS-B aircraft positions with the RTL-SDR. To run this program you will need an Android 4.0+ device with a decent processor, a USB OTG cable and an RTL-SDR dongle.
An Android app for listening to weather radio in the US and Canada. Can also decode EAS alerts. To run this program you will need an Android 4.0+ device with a decent processor, a USB OTG cable and an RTL-SDR dongle.
rtl_acars_ng is an improvement of the old rtl_acars command line based Linux ACARS decoder. It is capable of scanning multiple frequencies and has a built in airline database. See this post for some more information.
TVSharp is a simple analogue PAL/NTSC TV decoder. Due to the RTL-SDRs limited bandwidth in SDR mode it is only capable of decoding black and white images.
Unitrunker is a trunking control channel decoder and controller. It can be used in conjuction with general purpose SDR receiver software like SDR#, or the latest preview version can be used directly with the RTL-SDR. Unitrunker listens to a control channel, and then can correctly tune SDR# (via a plugin), or itself in the preview version to the correct channel in order to successfully follow a trunked voice conversation.
A trunking control channel decoder and controller. Supports most Motorola systems. Can connect directly to the RTL-SDR.
Trunk88
SDRTrunk (Windows/Linux/Java) (Free) – Trunking Control
SDRTrunk is a java based application for decoding and trunk tracking multiple analog and digital radio channels across multiple USB dongle tuners and/or sound card inputs from discriminator-tapped scanner radios.
rtl_power is a wideband spectrum monitor. This tool let’s you gather signal data over a very wide area of the frequency spectrum, and then that data can be used to find active areas of the spectrum.
Kalibrate-rtl is a command line Linux tool that is used to determine an RTL-SDR dongles frequency offset in PPM. It uses the time synchronization information in GSM signals to do this.
LibRedio is a tool which can decode temperature and humidity readings that are broadcast from many commercially available wireless environmental sensors.
PureData and Max/MSP are graphical programming tools for creating music, sound, video and interactive graphics applications. This software is a wrapper for RTL-SDR that allows the dongle to be used in these tools.
Software that allows you to visualize the output of a rtl_power scan using a generated waterfall image in a web browser. Shows the current frequency and time wherever the mouse is.
GNU Radio is a powerful digital signal processing (DSP) package for creating software defined radios. DSP programs can be written visually using block diagrams in the GNU Radio Companion software. It supports the RTL-SDR with an RTL2832U source block. Various decoders are written in GNU Radio and require it to be installed to run.
Redhawk is another digital signal processing package that is very similar to GNU Radio. It is designed to aid in the development, deployment, and management of real-time software radio applications
MATLAB is a well known mathematical computing language. With this support package MATLAB can interface with the RTL-SDR, and digital signal processing algorithm can then be written in MATLAB.
LabVIEW is a software package usually used for control systems engineering. With SDR Lab, the RTL-SDR is able to interface with LabVIEW.
Programs Compatible Through Piping
These programs do not directly access the RTL-SDR but are compatible with the RTL-SDR either through piping of the audio output via software like VBCable, Virtual Audio Cable, Windows Stereo Mix, Linux pipes or a physical Audio Cable or via receiving RTL-SDR received data through some other way such as through a network. Most of these are general ham radio programs that have found wider use with the RTL-SDR.
WxToImg to a program which can be used to decode NOAA weather satellite data and then display and post process the weather images. Use in conjunction with a general purpose SDR receiver and pipe the audio output to WxToIMG.
DSD is an acronym for digital speech decoder. It is a program that is capable of decoding digital speech codecs such as P25, DMR/MOTOTRBO, NXDN and D-Star. DSD+ is a new version of DSD which has the same features as DSD, but has improved decoding performance. For DSD you will need to copy cygwin.dll into the same direction as dsd to run the program. For DSD+ you won’t need cygwin, but instead you will need lame_enc.dll. Use in conjunction with a general purpose SDR receiver and pipe the audio output to DSD/DSD+.
There is now also the in development DSD 1.7 which supports new features like D-Star voice decoding.
DREAM is a Digital Radio Monodiale (DRM) decoder. You will need an upconverter to receive DRM signals with the RTL-SDR as they are on the HF band. To use DREAM you’ll need to also compile or download an AAC decoder dll file, see our tutorial for a pre-made .dll. Use in conjunction with a general purpose SDR receiver and pipe the audio output to DREAM.
SondeMonitor is commercial software with a 21 day free trial that is used to decode various weather balloon (radiosonde) telemetry signals. Use in conjunction with a general purpose SDR receiver and pipe the audio output to SondeMonitor.
dl-fldigi (Windows/Mac/Linux) (Free) – High Altitude Balloons
A modification of fldigi that can receive telemetry from amateur high altitude balloons (HABs). Use in conjunction with a general purpose SDR receiver and pipe the audio output to dl-fldigi.
PlanePlotter is a commercial advanced graphical ADS-B radar display with a 21 day free trial. With the RTL-SDR, use in conjunction with an ADS-B decoder. PlanePlotter also has an excellent ACARS decoder. To use the ACARS decoder, use with a general purpose SDR receiver and pipe the audio output to PlanePlotter.
Virtual Radar Server is a free program which will display ADS-B data on a Google Maps window. With the RTL-SDR, use in conjunction with an ADS-B decoder.
Acarsd is a free ACARS decoder program. It contains a database of aircraft and will display their images if they exist. Use in conjunction with a general purpose SDR receiver and pipe the audio output to Acarsd.
ShipPlotter is a commercial program which can plot ship positions on a nautical map or Google maps from decoded AIS datastreams. It has a 21-day free trial. Use in conjunction with a general purpose SDR receiver and pipe the audio output to ShipPlotter.
AISMon is a free AIS data decoder. It can output decoded AIS data through a UDP stream for use in other programs that display the ship positional data such an OpenCPN. Use in conjunction with a general purpose SDR receiver and pipe the audio output to ShipPlotter.
OpenCPN is a free nautical AIS mapping tool which can display ship positions on a map using AIS data. Use this software in conjunction with a program that decodes AIS data, such as AISMon.
RDS Spy is a free and very sensitive Radio Data System (RDS) decoder. Use in conjunction with a general purpose SDR receiver and pipe the audio output to RDS Spy.
Orbitron is a free satellite tracker. With a plugin, Orbitron can be made to control the tuned frequency in SDR# allowing for automatic satellite tracking, and doppler effect correction. Use in conjunction with the Orbitron SDR# plugin.
AFSK1200 is an AFSK1200 decoder. This mode is used by APRS radio hobbyists. Use in conjunction with a general purpose SDR receiver and pipe the audio output to AFSK1200.
This is a program designed to decode the Funcube satellite telemetry data. Use in conjunction with a general purpose SDR receiver and pipe the audio output to the dashboard.
Spectrum Lab is a free specialized audio analyzer, filter, frequency converter, hum filter, data logger. It is usually used in the field of radio astronomy for things like meteor detection. Use in conjunction with a general purpose SDR receiver and pipe the audio output to Spectrum Lab.
Baudline is a free audio spectrum analyzer usually used to analyze radio data signals. Use in conjunction with a general purpose SDR receiver and pipe the audio output to Baudline.
HROFFT is a specialized audio analysis software program designed for monitoring meteor scatter signals. Use in conjunction with a general purpose SDR receiver and pipe the audio output to HROFFT.
multiPSK(Windows) (Free for non-commercial use) – Ham digital mode decoder
multiPSK is a popular ham digital mode decoder and supports a very wide range of digital modes. It also directly supports connecting to the RTL-SDR via RTL_TCP.exe. You will need to download the rtlsdr official Windows release, and copy the rtl_tcp.exe, rtlsdr.dll, pthreadVC2-w64.dll and libusb-1.0.dll into the same directory as multipsk.exe to use this option. Otherwise you can simply pipe the audio from a general purpose SDR receiver into multiPSK.
Fldigi (Windows/Mac/Linux) (Free) – Ham digital mode decoder
Fldigi is a free software program capable of decoding various ham radio digital data signals such as CW, Contestia, Domino, Feld Hell, Olivia, MT63, PSK, RTTY, Thor and WEFAX. Use in conjunction with a general purpose SDR receiver and pipe the audio output to Fldigi.
multimonNG (Windows/Mac/Linux) (Free) – Ham digital mode decoder
multimonNG is a fork of the multimon software. It is a general purpose decoder capable of decoding POCSAG512, POCSAG1200, POCSAG2400, EAS, UFSK1200, CLIPFSK, AFSK1200, AFSK2400, AFSK2400_2, AFSK2400_3, HAPN4800, FSK9600, DTMF and ZVEI. Use in conjunction with a general purpose SDR receiver and pipe the audio output to MixW.
MixW is a free software program used for decoding various digital ham radio signals. It is capable of decoding CW, BPSK31, QPSK31, FSK31, RTTY, Packet, Pactor, Amtor, MFSK, Throb, MT63, Hellschreiber, WEFAX and SSTV. Use in conjunction with a general purpose SDR receiver and pipe the audio output to MixW.
Sorcerer is a free software program capable of decoding a wide range of ham radio signals. Sorcerer is known for its decoder support for rarely used signals, but it is mostly used to decode STANAG 4285 signals. Use in conjunction with a general purpose SDR receiver and pipe the audio output to Sorcerer.
Sigmira (Windows/Linux) (Free) – Ham digital mode decoder
Sigmira is a free software program that is capable of decoding a wide range of ham radio signals. Sigmira is best known for it’s support for decoding the “Japanese Navy Slot Machine” signal and STANAG4285 signals. Use in conjunction with a general purpose SDR receiver and pipe the audio output to Sigmira.
Rivet(Windows/Mac/Linux) (Free) – Ham digital mode decoder
Rivet is a free open source decoder for various spy agency and numbers station related HF signals such as Baudot, CCIR493-4, CIS36-50, CROWD36, FSK200/500, FSK200/1000, FSK, GW FSK, XPA and XPA2.
CWSkimmer is a Morse code (CW) decoder. It is generally regarded as one of the best CW decoders available. Use in conjunction with a general purpose SDR receiver and pipe the audio output to CWSkimmer.
Taxidecoder is a free mobile data terminal (MDT) decoder. It will only work in countries that use MDT data signals that taxi decoder supports. Use in conjunction with a general purpose SDR receiver and pipe the audio output to taxidecoder.
The Meteor-M N2 is a polar orbiting Russian weather satellite that was launched on July 8, 2014. Its main missions are weather forecasting, climate change monitoring, sea water monitoring/forecasting and space weather analysis/prediction.
The satellite is currently active with a Low Resolution Picture Transmission (LRPT) signal which broadcasts live weather satellite images, similar to the APT images produced by the NOAA satellites. LRPT images are however much better as they are transmitted as a digital signal with an image resolution 12 times greater than the aging analog NOAA APT signals. Some example Meteor weather images can be found on this page and the satellite can be tracked in Orbitron or online.
The RTL-SDR and other SDRs like the Funcube along with some free software can be used to receive and decode these images. LRPT images from the Meteor-M N2 are transmitted at around 137.1 MHz, so any satellite antenna like those commonly used with the NOAA weather satellites can be used.
The tutorial also shows an alternative and faster Linux based method using some GNU Radio scripts, but with the final processing still done with Oleg’s decoder in Windows.
The Meteor-M2 SatelliteAn Example LRPT Image Received with an RTL-SDR from the Meteor-2 M2.Another Sample LRPT ImageWhat a LRPT signal looks like in SDR#
For a comprehensive book about the RTL-SDR you may be interested in our eBook available on Amazon.
The reception process is to essentially record an IQ file of an LRPT transmission using SDR#, reduce the sample rate of the IQ file using audacity and then decode the file using LRPTrx.exe. Then finally the decoded data can be imported into LRPTofflineDecoder to produce an image.
Over on YouTube user max30max31 aka IZ5RZR has uploaded a video that shows a faster method for decoding Meteor M2 weather satellite images on a Windows system. The Meteor-M N2 is a Russian weather satellite that transmits images using the LRPT protocol at around 137.1 MHz with can be received with an RTL-SDR. Compared to NOAA satellite APT images, LRPT images are much higher in resolution.
Normally, decoding Meteor M2 LRPT images requires a post processing step which involves the use of Audacity, an audio editing suite to reduce the recorded IQ files sample rate. However, with the recently released decimation SDR# drivers the Audacity step can be avoided by using a an appropriate decimation factor (8 at 1.024 MSPS) when recording the LRPT signals IQ data.
Back in September last year we posted a tutorial written by RTL-SDR.com reader Happysat which showed how to receive and decode high resolution Meteor-M2 LRPT satellite images. The tutorial required several offline manual processing steps to be performed and therefore could not decode the image in real time.
At the same time Vasili has also released another plugin called DDE Tracker which allows a satellite tracking program such as Orbitron to interface with and control SDR#. The plugin can be downloaded on the same page as the QPSK plugin. This is similar to the already existing DDE plugins, but now also comes with a scheduler which allows users to automatically schedule recordings of Meteor-M2 and NOAA satellite passings.
Tutorial
To help users get set up with this new method, Happysat has again come forth with another tutorial which can be downloaded here (.pdf) (.docx) (.txt w/ images in .rar). At first glance the tutorial may seem more complicated than the old method, but in the end it is a much faster and more efficient way at decoding LRPT images. The basic steps involve setting up Orbitron and the DDE plugin to automatically track the Meteor-M2 LRPT satellite and signal, and then setting up the QPSK plugin and the new version of Lrptdecoder to talk to one another in real time via a local TCP connection.
Real time decoding of Meteor-M2 with two new SDR# Plugins.QPSK Demodulator SDR# PluginDDE Orbitron Interface SDR# Plugin.
AMIGOS
One more Meteor-M2 related thing to look forward to in the future is the AMIGOS project which stands for Amateur Meteor Images Global Observation System. This will be a system where users around the world can contribute LRPT images through the internet to create a worldwide LRPT receiver. Oleg of LrptDecoder writes:
There is an idea to merge LRPT receive amateur radio stations in a network through the Internet and create a super LRPT receiver. I see the benefit of professionals from the control center in the operational monitoring of the condition of the equipment MSU-MR, and for fans of the fullest reception of images from Meteor-M.
All is in testing phase and need some setup for the servers, data is beeing shared thru a VPN connection to a central server which will have a continous flow of images from all over the world. Users can join and share in realtime the data more info on: http://meteor.robonuka.ru/for-experts/amigos/
What is Meteor-M2?
If you don’t understand what all this is about: The Meteor-M N2 is a polar orbiting Russian weather satellite that was launched on July 8, 2014. Its main missions are weather forecasting, climate change monitoring, sea water monitoring/forecasting and space weather analysis/prediction.
The satellite is currently active with a Low Resolution Picture Transmission (LRPT) signal which broadcasts live weather satellite images, similar to the APT images produced by the NOAA satellites. LRPT images are however much better as they are transmitted as a digital signal with an image resolution 12 times greater than the aging analog NOAA APT signals. Some example Meteor weather images can be found on this page and the satellite can be tracked in Orbitron or online.
A software defined radio such as the low cost RTL-SDR, or the higher end Airspy and Funcube dongles can be used to receive these signals.
An Example LRPT Image Received with an RTL-SDR from the Meteor-2 M2.
Updates
The DDE plugin can also be used for tracking NOAA satellites. Some people have been having trouble with set up. Happysat writes a solution:
Over on YouTube user max30max31 (a.k.a IZ5RZR) has uploaded a video showing some of the steps in the tutorial as well as the real time result of decoding of the weather satellite image.
The RTL-SDR software defined radio is often used to receive signals from NOAA APT weather satellites. Once decoded these signals produce a freshly captured image of the earth over your current location. We have a simple tutorial on setting this up here.
However, recently Marco Johansson wrote into RTL-SDR.com to explain an alternative method to the one described in our tutorial. His method uses rtl_fm as the receiver instead of the GUI based software SDR# and uses several other pieces of software to automate the whole process. Marco believes that his method may be useful for some people and his tutorial is presented below. Also, if you are interested Marco has a WxtoImg generated webpage which shows all his recently received images here wxsat.haastaja.net.
A composited weather satellite image made up of several images received from NOAA satellites by Marco Johansson
Note that the following tutorial is written by Marco Johansson.
Marco’s NOAA APT Decoding Tutorial
As a Windows user I had some serious problems using an RTL-Dongle as a receiver for WxtoImg. Signal drops, CPU load, and no receiver control. I had to use 5 different pieces of software to get automatic reception to work and every day one of the programs had some weird problems causing the whole system to stop working. I read several forum posts about similar problems. A huge bit of help came from WxtoImg’s own forum where a user told how he was able to use rtl_fm as a receiver. His system was Linux based, so I was not able to use his scripts, but it gave me enough information to find a Windows based solution.
I stumbled on to a software program that solves my problem totally. It is originally made to control Windows MCE (Media Center), but since it’s release it has been enhanced to work as a universal remote control for the Windows system.
In WxtoImg I selected “Baykal” receiver, port COM1 and 2400baud. The protocol for remote control is very easy to understand and after every command WxtoImg sends CR/LF to receiver, which is mandatory to get commands to work.
Control commands are handled with MCE controller. It listens to COM2 (bridged with COM1) and when it hears a valid command string (A Magic ‘word’) it activates a task. Tasks are .bat files, one for every satellite and a “kill” to stop receiver after the satellite pass.
When satellite is coming (one minute before it is over head) WxtoImg sends a command “MUA” that triggers “kill.bat”. Then WxtoImg sends a command “RF0xxxxxxx” where xxxxxxx is the frequency of the satellite, “1371000” for NOAA19 – this triggers “rec-noaa19.bat”. When the pass is over, Wxtoimg sends again “MUA” to kill the receiver program.
Now I can control recordings directly from WxtoImg without any other software (Orbitron, SDR#, DDE client etc).
.bat files and other configurations are provided below for others to use. I ended up to have separate .bat to start the tasks as in that way I can set the system start and stop recording in the background without a command prompt popping around my desktop every 90 mins
My system is Windows 8.1, I have not tested this in 7, 8 or 10 but I believe it should work without any modification. The HW ID of the RTL-Dongle I use for wx_rtl_fm.exe is “3” (‘-d 3′ in script). If you have only one RTL-Dongle, then this should be set to “0”. I use the bandwidth of 55 kHz that seems to be enough for good APT reception including doppler error as in this method the doppler error is not corrected in the receiver at all (no AFC).
NOTE! I have copied the original ‘rtl_fm.exe’ to ‘wx_rtl_fm.exe’ to be able to start other rtl_fm.exe instances without the risk that WxtoImg kills my other receiver accidentaly. And of course, remember that these are from my system and the correct path used in scripts will be different for you Also, the original ‘sox.exe’ is copied to ‘play.exe’ as instructed in the SoX’s manual for Windows user. And because I’m lazy, I copied rtl_fm and SoX binaries to same directory so that I do not have to put so long path strings into my .bat scripts
Final words:
.bat’s used in this are very dirty hacks and there are lot’s of improvement available for sure – but it works! Also, the remote protocol for Baykal receiver actually sends two more commands, one is used for telling the modulation of the transmission (RM NFM) and second to do something I do not know (MUF).
The whole communication in my system goes like this:
1) “MUA” => Kill all wx_rtl_fm.exe processes currently running (if any). This happens one minute before satellite pass starts.
2) “RF0xxxxxxx” => Start wx_rtl_fm & SoX, xxxxxxx=frequency of the satellite and is used to select correct .bat for different satellites (see MCE Control XML-file for details). This happes when satellite pass starts.
3) “RM NFM” => Not used in my system. Could trigger something fun if needed :). This happens right after ‘RF0xxxxxxx’ command.
4) “MUF” => Not used in my system. Could trigger something fun if needed :). This happens right after ‘RM NFM’ command.
5) “MUA” => Kill all wx_rtl_fm.exe processes currently running. This happes right after satellite pass.
SoX is a very powerfull tool for audio manipulation. There are options that could greatly improve the audio quality of the received signal – denoice, better dynamics etc. I am not that keen to try everything SoX could do as the results are already very good in my system, but if there are someone who knows better ways to handle SoX then please do not hesitate to comment!
Used .bat Files
“Kill the receiver”:
kill.bat is triggered by MCE control and calls kill-wx_rtl_fm.bat to do the actual killing.
kill.bat
cd C:\Users\Mac Radio\ownCloud\SDR\rtl_fm_sox
start /min kill-wx_rtl_fm.bat ^& exit
This triggers;
kill-wx_rtl_fm.bat
taskkill /IM wx_rtl_fm.exe /F
“Start recording”:
Recording is started after MCE Control gets the correct ‘word’ from WxtoImg. For every satellite there are separate ‘words’ and separate .bat files.
rec-noaa15.bat
cd C:\Users\Mac Radio\ownCloud\SDR\rtl_fm_sox
start /min noaa15.bat ^& exit
This triggers;
noaa15.bat
cd C:\Users\Mac Radio\ownCloud\SDR\rtl_fm_sox
play -r 55k -t raw -e s -b 16 -c 1 "|wx_rtl_fm -d 3 -M fm -f 137.62M -s 55k -l 0" -t waveaudio
rec-noaa18.bat
cd C:\Users\Mac Radio\ownCloud\SDR\rtl_fm_sox
start /min noaa18.bat ^& exit
This triggers;
noaa18.bat
cd C:\Users\Mac Radio\ownCloud\SDR\rtl_fm_sox
play -r 55k -t raw -e s -b 16 -c 1 "|wx_rtl_fm -d 3 -M fm -f 137.9125M -s 55k -l 0" -t waveaudio
rec-noaa19.bat
cd C:\Users\Mac Radio\ownCloud\SDR\rtl_fm_sox
start /min noaa19.bat ^& exit
This triggers;
noaa19.bat
cd C:\Users\Mac Radio\ownCloud\SDR\rtl_fm_sox
play -r 55k -t raw -e s -b 16 -c 1 "|wx_rtl_fm -d 3 -M fm -f 137.1M -s 55k -l 0" -t waveaudio
And finally, the MCE Control magic ‘words’. By default, MCE Control understands over 200 separate commands originally meant to remote control Windows MCE (Media Center). Fortunately, one can create their own commands and get MCE Control to do much more – control Wx-system!
MCE Control uses an XML configuration file for these extra commands. The file is located in the same directory where the main executable is located. My system uses following XML file to be able to control ‘wx_rtl_fm.exe':
<?xml version="1.0" encoding="utf-8"?>
<MCEController xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<Commands xmlns="http://www.kindel.com/products/mcecontroller">
<!-- Place command definitions here -->
<!--
==================================================================
StartProcess Commands
File: The full path to the executable you want to start.
==================================================================
-->
<StartProcess Cmd="RF01376200" File="C:\Users\Mac Radio\ownCloud\SDR\rtl_fm_sox\rec-noaa15.bat"/>
<StartProcess Cmd="RF01379125" File="C:\Users\Mac Radio\ownCloud\SDR\rtl_fm_sox\rec-noaa18.bat"/>
<StartProcess Cmd="RF01371000" File="C:\Users\Mac Radio\ownCloud\SDR\rtl_fm_sox\rec-noaa19.bat"/>
<StartProcess Cmd="MUA" File="C:\Users\Mac Radio\ownCloud\SDR\rtl_fm_sox\kill.bat"/>
</Commands>
</MCEController>
Pete’s tutorial starts from a fresh install of Ubuntu and uses GQRX, GNU Radio Companion, WxtoIMG and the MeteorM2 decoding tools. He shows how to set up the audio piping within Linux, how to run the MeteorM2 LRPT Offline decoder Windows tool in Wine, a Linux Windows emulator and how to use WxtoIMG together with GQRX.
The NOAA and Meteor M2 weather satellites transmit images that they have taken of the earth. With an RTL-SDR and appropriate antenna you can receive these images. On this blog we have Windows tutorials on receiving NOAA and Meteor M2 satellites.
The Windows LRPTOfflineDecoder tool running in Linux with Wine.
Recently a reader of our blog, Initrd, wrote in to let us know about a new tutorial he created that shows how to set up a dual NOAA APT and Meteor LRPT weather satellite monitoring station with an RTL-SDR dongle. These weather satellites transmit a live image of the portion of the earth that they are currently over, providing a valuable tool for weather analysis. APT transmissions are analogue and are transmitted by the American NOAA satellites, and the newer Meteor M2 satellite transmits a higher resolution image in the LRPT format. We also have posted separate tutorials that show how to set up NOAA APT and Meteor M2 LRPT decoding with an RTL-SDR, but Initrd’s tutorial appears to be a good all in one guide.
His tutorial takes you step by step through a process that involves setting up the satellite tracking software Orbitron, all the required SDR# plugins, the APT decoder WXtoIMG and the LRPT decoder. The tutorial also shows how to connect them all together and set them up so that APT and LRPT decoding can coexist.
The Meteor M N-2 is a polar orbiting Russian weather satellite that was launched in July 2014. It transmits with the LRPT protocol which allows us to receive weather satellite images that are of a much higher resolution than the NOAA APT satellites. For a while since the launch RTL-SDR users had a good time receiving beautiful images from Meteor M-N2, but unfortunately since late last year the N2 LRPT transmitter has been turned off, due to technical problems with the IR sensors as cited by Russian meteorologists.
Fortunately for Meteor N2 enthusiasts the old Meteor M N1 satellite which was thought to be dead sprung back into life around November 2015. Recently Matthew A., a reader of our blog wrote in to let us know that while N2 is still not transmitting, N1 is still transmitting, albeit with somewhat distorted images. Matthew also mentions this link: http://homepage.ntlworld.com/phqfh1/status.htm, which contains up to date info on the status of all weather satellites. He also writes:
While transmissions are readily detectable and decodable at night, it seems that M N-1’s infrared sensors are not functioning. Yielding only black, with the typical noise bars of Red, Green, or Blue
As has been previously mentioned, Meteor MN-1’s stabilization system has obviously failed, and the horizon is clearly visible. Perhaps not of scientific value, but certainly beautiful.
We also note that there are several comments over on the Meteor-M N2 news and support website regarding receiving images from N1 and N2. It seems that sometimes N1 also has some problems with transmission, but they are usually quickly fixed.
In order to optimally receive NOAA weather satellite images a special satellite antenna tuned for 137 MHz should to be built. Generally either a QFH or turnstile antenna is recommended as these receive signals coming from the sky very well. If you are interested in receiving weather satellite images from NOAA satellites with an RTL-SDR dongle then we have a tutorial available here.
While QFH and turnstile antennas are not difficult or expensive to build, they still do require a small amount of electrical and construction skills. Over on YouTube user Wanderlinse shows us a possible alternative NOAA antenna that is simply made out of an old umbrella (the video is narrated in German, but it is easy to understand from the visuals). He uses a short BNC cable with crocodile clips, and connects one clip to the spines of the umbrella, and the other to the central metal shaft. For some reason this seems to create a good antenna that receives NOAA APT signals very well. To prevent wind issues he also cuts out some holes in the umbrella fabric.
Wanderlinse also shows that he can receive other signals with this umbrella antenna too, such as long wave, medium wave, shortwave, aircraft radio and ham radio.
According to various reports the Russian Meteor M-N2 satellite appears to be active again once more. The Meteor M N-2 is a polar orbiting Russian weather satellite that was launched in July 2014. It transmits with the LRPT protocol which allows us to receive weather satellite images with an RTL-SDR that are of a much higher resolution than the NOAA APT satellites.
Unfortunately late last year Meteor M N-2 had some problems and LRPT transmissions were turned off for the time being. During this downtime the Russian space agency switched the LRPT transmitter on the older Meteor M N-1 satellite back on, even though the satellite was tumbling in orbit. Currently people are not reporting any signal from Meteor M N-1, so this may have been turned off, perhaps temporarily.
Now however, it seems that Meteor M N-2 has been switched back on again and various people have already successfully received its signal. If you want to receive these Meteor M N-2 weather images with an RTL-SDR dongle or other SDR then you can view the tutorial written by Happysat here.
It is well known that the NOAA satellites broadcast weather satellite images which can be received and displayed with an RTL-SDR and computer. What is less known is that there is a telemetry beacon that is also transmitted by the same satellites. The telemetry not only contains data such as the current spacecraft time, day and ID, but also contains scientific data from on board instruments such as:
The HIRS/3 and HIRS/4 instruments which is a high resolution infrared sounder which can be used to create a low resolution multi-spectral scan of the earth. (more info)
The Space Environment Monitor (SEM-2) which has a Medium Energy Proton and Electron Detector (MEPED), and a Total Energy Detector (TED). This experiment is used to measure the effect of the sun on satellite communications. (more info)
The experimental DCS/2 transmitter which retransmits signals from 401.65 MHz sea buoys, arctic fox collars, sea ice monitors, weather balloons and more. (more info pdf)
The ARGOS Advanced Data Collection System (ADCS) which amongst other uses is used in research for tracking animal GPS collars around the world.
Over on Reddit user merg_flerg has uploaded an imgur post that carefully details a step by step guide for building a double cross antenna. A double cross antenna is great for reception of satellites like NOAA and Meteor since it has a sky oriented radiation pattern with very few nulls. This means that it can receive satellite signals coming from the sky well. Alternative antennas for NOAA/Meteor include turnstiles and QFH antennas, although the double cross antenna seems to have the least nulls, meaning that the signal is less likely to fade in and out as the satellite moves across the sky.
merg_flerg’s design is also modified from the standard design slightly, allowing it to become easily disassembled and carried within a backpack. At the end of his tutorial he writes that he gets much better reception with his double cross antenna than he does with his QFH.
In the post he demonstrates the final constructed antenna decoding a NOAA APT weather satellite image with an RTL-SDR and the WXtoIMG software. See our tutorial for information on decoding NOAA weather satellite images.
The finished double cross antenna connected to a PC running an RTL-SDR and WXtoIMG.
A few days ago we reported that the Outernet L-band satellite service had just upgraded their software to make it available for receiving APRS and weather updates. Back then it wasn’t clear what the weather updates would entail. Today weather updates starting being transmitted. They are using NOAA data and displaying it on a live weather app (which can also be viewed online here).
The app can be used to view weather data such as wind vectors, temperatures, relative humidity, total precipitable water, total cloud water, mean sea level pressure and ocean currents. Outernet writes that the global weather data will be updated via their satellite system once per day, and that each update also provides 24h, 48h and 72h predictions.
We also see that grib files for mariners are now coming in as well as several Wikipedia articles and regular APRS broadcasts from the ISS.
It looks like the Outernet service is becoming more and more useful over time. If you are interested in receiving Outernet with an RTL-SDR see our tutorial post here.
Over on YouTube Adam 9A4QV has uploaded a video showing how to build a DIY bandpass filter for 137 MHz. This can help improve the reception of NOAA and Meteor M weather satellites, by blocking strong out of band signals. Adams design is a 132 MHz – 142 MHz Butterworth bandpass filter which gives about 35 dB attenuation outside of the pass band. He’s also posted a write up documenting the filter design on his website.
Lucas Teske recently went ahead and built the 137 MHz filter suggested by Adam. Lucas didn’t have the correct capacitor values so he ended up cascading several in series. His results showed that the filter did improve his reception significantly.
