How to Receive HRPT
Watch the Road to HRPT Playlist
I made a few Videos about my journey to receiving HRPT Signals and decoding them into nice Images. It's a good startpoint for everyone that want's to get started. The Videos are in German, but i added English subtitles. Also See the Following two Blog Post by me: HRPT first images, HRPT optimizations and great images
Down below you find Information about Hardware and Software that is used to Receive HRPT images at the Moment as well as my recommendation to get started with dowloading awesome Images from Weather Satellites Orbiting Earth like the one Below.
Curently the Following Satellites can be received on L-Band that all transmit a HRPT Signal:
- NOAA15 (very weak)
- Meteor M2 (Weak, broken Antenna)
- Meteor M2-N2
- MetOp A (only active in some Areas)
- MetOp B
- MetOp C
- FengYun 3B
- FengYun 3C (Now active only over China)
You can use a normal Satellite Dish as you use for Receiving TV via Satellite. It should be at least 80cm in Diameter, a 1m sized one would be the sweet spot in my opinion. You can get them on ebay, Amazon or your local Hardware Store etc. for under 100€ if you go for a 1m one. If you want professional (but expensive) mesh dishes take a look at rfhamdesign
The Feed is similar to a LNB on a TV Dish and receives the Signal that the Dish focused onto it. The Feed can be build quite cheaply by yourself and there are many different options:
- Cantenna Just a Metal Can with a Signal Probe, very Easy
- Helical Feed A Wire Helix that is mounted ona metal plate
- Patch Feed Two metal Plates in a specific distance from each other
Amplifier / LNA
The Signals that arrive at the Feed are quite Weak, so you need a Amplifier that you don't lose everything in the Cable to your Receiver. A filtered one also removes unwanted Signals and improves Signal qwuality with that what is very good. There are many Options, but a cheap and very good working one is the Nooelec SawBird+ GOES. It can be powered by MicroUSB or over Bias-T from your SDR.
The Receiver is a important component because it converts the Analog Signal into a Digital one that you PC can handle. You can get soemthing with a RTLSDR, but you will never get a clean image with that because it is not good enough in many different sections. The cheapest way is to get yourself a Airspy Mini, that is good for all HRPT Satellites and it is a great SDR all around.
Of course you need a Computer to connect to your SDr, but you should use a PC or Notebook that is powerful enough. It's stange to many because the Notebook was never a bottleneck, but if you decode HRPT Signals live even a decent i5 Notebook can struggle. In my experience a modern i5U is good for NOAA and Meteor Satellites, a i7U is okay for all Satellites. As an alternative you can use a not so powerful PC and record the Signal and prosess it later.
The Satellites are all moving in relation to you on Earth, so you need to follow them with the Antenna as they fly by. You can get a expensive Antenna Rotor if you wan't but you should be fine with just moving the Dish by Hand. It takes some time to get used to it but you can get very nice Images even with this "low tec" method. It also makes more Fun tracking by Hand when you get it right in my opinion :)
Besides the Main Components you will need some SMA Cables to connect SDR, LNA and Feed. A few USB Cables are also needed to supply your LNA with Energy and connect your SDR etc.
To know where and when a Satellite flys by you will need some Software that can calculate that. If you use a Antenna Tracker it should also automatically follow the Satellite. There are many Options, here are some good ones:
- Orbitron Old but still Awesome! (FREE)
- WXTrack a good allrounder by HRPT_Reader writer David Taylor (FREE)
- gPredict a good Tracking software for use on Linux / Mac (FREE)
- UltraTrack nice Software by HRPT Decoder writer USA-Satcom (Paied)
Gnuradio is a platform that makes it possible to build Signal Processing Software with building Blocks. It is avaliable on Windows and Linux for Free and can be used to Decode HRPT Signals. You can live Decode Signals from NOAA and Meteor Satellites, for MetOp and FengYun you can only Demodulate the Signals and you will need other Software to further process them. See the Link below for Downloading the Flowgraphs on this Website.
xHRPT is a piece of Windows only Software from USA_Satcom that is NOT free but a very nice package. It is very comfortable and has some very good Signal processing, so you get cleaner images when the Signal is weak. It can live Decode all Satellites including MetOp and Fengyun, but you need a powerful PC for that. If needed you can use the Demod only mode and process it later with the Standalone Decoder.
To view the Decoded Data as an Image you will need a Software that can Read the files that the Decoder Produced. The recommended Software is HRPT Reader by David Taylor that you can get for Free on satsignal.eu. There is a paied Versions with soem Extras, but the Free one really has anything you need to get some great images out of it.
USA_Satcom also programmed a little tool to decode demodulated Signals saved in raw files from metOp And FengYun Sats. It is not Free but it can be used in combination with gnuRadio or xHRPT Demod only Mode. For xHRPT users it's included in the License. There also is a Decoder made by @Aang254 that is free to use and Open Source. It can handle the same raw / bin files from GnuRadio.
MetOp and FengYun satellite Files decoded need further Processing before they can be viewed in HRPT Reader. For that there is a little Software Tool that can do that for you. You find the Download and more information under the following Link.
NOAA with GnuRadio - Free and Easy
The easiest and cheapest way to get an HRPT Image out of the Radio waves you receive is to use GnuRadio to Decode NOAA Satellites, with that there is no Software Cost associated. Install Gnuradio including gr-noaa on your Windows or Linux PC, download our Flowgraphs that are provided by Peter and make sure your SDR is recognised by GnURadio.
Get everything Ready
Make sure your Dish including Feed and LNA is all connected correctly including your SDR. Check that your SDR is connected to your PC and that the LNA is powered (LED should be lit). If you use a Tracker make sure you have it setupo correctly, if you track by Hand it is helpfull having a Tracking Software Open to have a reference where the Satellite is. If thats okay your Hardware should be good to go!
Start the Flowgraph
Open GnURadio, Open the flowgraph and start it up when the Satellite comes into view. You can see the Signal of the Satellite in the Spectrum, the Signals from NOAA Satellites have a Carrier that is really String, that's the first Thing you should see when the Sat come sinto View and you are pointed ruffly in the right direction.
Receive the Satellite
Aim for the best Signal possible by adjusting the Gain of the SDR and make sure the Antenna is tracking the Satellite correctly (if you have a good setup Rotor all should be fine, important for Handtracking). You can Stop/Close the Flowgraph as soon as you lose the Signal of the Satellite.
Open your Image!
Start HRPT Reader and Open the File you Decoded from the Satellite with the Gnuradio Flowgraph before. Select the right Satellite in the Popup and if it was a North or Southpass. Voila, you should now see your Image on the Screen!
Down Below you see a Overview of the Current Ecosystem around the xHRPT Decoder by USA_Satcom. It shows quite well how you go from a Signal on your SDR to a nice Image with Software from USA_Satom as well as the GnuRadio Metop/FengYun Standalone Demodulator.