Crowd Supply is hosting Teardown Session 38 on Thursday 3- November at Noon PST time which will feature the Discovery Dish. Join us for this livestream where I will be talking about and showing the Discovery Dish prototype.
Discovery Dish is currently being crowd funded over on Crowd Supply. It is designed to be an easy entry to the world of L-band weather satellites, hydrogen line radio astronomy, and Inmarsat reception. The Discovery Dish aims to be the start of an ecosystem of hardware designed to get users set up with satellite reception, including a planned companion light-duty antenna rotator.
Remember to click on the “Notify me” button on the YouTube link in order to be reminded about the stream!
Over on his YouTube channel "saveitforparts" has uploaded a video where he uses an umbrella, pin tin and tin foil tape to create a simple dish antenna for receiving GOES, NOAA and METEOR HRPT satellites.
The full build consists of an umbrella covered in tin foil tape, a helical wire feed on a pie tin, a filtered LNA, an RTL-SDR and an Android phone running SDR++. While he did have initial success at receiving, he soon decided to swap out the helical wire feed for a PCB linear feed instead which worked much better as helical feeds can be very difficult to get right.
Through the video saveitforparts goes over the failures he had, in the end noting that it's not a great antenna, but it's something that can be used in a pinch.
We also want to remind readers that we are currently Crowd Funding for our Discovery Dish, which will be a low cost way to get into L-band satellite reception.
Before this update, to automate the reception and decoding of APT and LRPT satellites a Windows PC, and a huge stack of various decoding and tracking programs and SDR# plugins are required, some of which are now even abandonware.
For APT a typical chain was SDR# -> DDETracker -> Orbitron -> WXtoIMG and for LRPT a typical chain is SDR# -> DDETracker -> Orbitron -> LRPT Demodulator -> LRPT Decoder -> SmoothMeteor -> MeteorGIS. Setting this chain of programs up can obviously be a lot of hard work.
The latest version of SatDump adds automation features which means these two entire chains can be replaced with just one program - SatDump. SatDump is available for Windows, Linux and Mac, so it can even run on something like a Raspberry Pi 5 or Orange Pi 5.
We decided to develop Discovery Dish because we were disappointed by the lack of ready-to-use, low-cost, lightweight dish antennas on the market that are suitable for software-defined radio projects like receiving L-Band geostationary and polar-orbiting weather satellites, as well as for 1.5 GHz Inmarsat reception and 1.42 GHz hydrogen line radio astronomy. With excellent open source weather satellite decoding software, like SatDump, now available, it’s time for a complementary, easy-to-use hardware solution.
Through testing over several years, we chose 65 cm as the diameter, as we found that 60 cm is close to the minimum diameter required for perfect GOES weather satellite reception at 24° elevation, so this size should be suitable for most of the world that has GOES reception available. For LRPT satellites like GK-2A, and HRPT polar-orbiting satellites, it is more than large enough. We combined the dish with a carefully tuned feed that has a built-in low-noise amplifier (LNA) and dual filtering, which means there is no loss from feed to LNA. This also means we can use thinner and less stiff coax cable, which is a lot easier to handle and route. Finally we ensured that the entire dish and feed system is waterproof.
The only other ready-to-use dish offering we found is based on a modified 2.4 GHz grid Wi-Fi dish, which is still in our opinion too big and heavy. Size and weight is especially the important if you want to be able to use a low-cost, light-duty antenna rotator, which typically can only handle less than 1 kg in weight. We found that the grid Wi-Fi dish offering also has no solution for waterproofing the LNA, so the LNA needs to be placed indoors and very thick and unwieldy coax is used to avoid feed to LNA losses.
Other ways to receive these weather satellites and carry out hydrogen line experiments typically involve modifying a 2.4 GHz Wi-Fi grid antenna, or an old satellite TV dish. But these modifications can be time-consuming and difficult to get right, and even 60 cm satellite TV dishes are too heavy for light-duty antenna rotators.
Finally, we developed Discovery Dish with an eye toward it being used with a low-cost antenna rotator, and we are in the process of prototyping our own rotator design. Our antenna rotator is not ready for crowdfunding yet, as there are still some things to work out and long-term stress testing to be done, but please keep an eye out for it in 2024! An antenna rotator is a great addition if you want to use a dish antenna to decode images from the polar-orbiting HRPT weather satellites.
Note that you don’t need an antenna rotator to receive geostationary satellites like GOES, or to do drift hydrogen line observations. For polar-orbiting HRPT satellites, the lightweight nature of Discovery Dish also makes tracking the satellites by hand a much easier prospect.
SatDump is a popular program that is used with RTL-SDRs and other SDRs for decoding transmissions from a wide array of weather satellites and their various imagers and sensors. Recently SatDump's author @aang254 has been working on improving the way projections work. Projections are essentially when the weather satellite image is stretched and skewed to fit correctly over the curved earth.
This means now that city markings and border lines should show up in the correct placed in any images received from SatDump.
If you're interested @aang254 has uploaded blog post on the SatDump website explaining the math, algorithms and problems he found when trying to get projections done right.
For the past few years we have been working on finding the best way to help beginners get started with L-band weather satellite reception and basic radio astronomy. We have now come up with a solution that we're calling the 'Discovery Dish' - a lightweight 65 cm diameter dish and active filtered feed set.
Discovery Dish: Simplified system for weather satellite reception and hydrogen line radio astronomy
Discovery Dish is a 65-cm diameter aluminum satellite dish and active filtered feed designed for receiving GOES HRIT, GK-2A LRIT, FengYun LRIT, NOAA HRPT, Metop HRPT, Meteor M2 HRPT and other weather satellites that operate around 1.69 GHz. The dish is designed to weigh under one kilogram, and it splits into three petals, making it easier to ship worldwide. The 1.69 GHz feed contains a built-in LNA right at the feed point, as well as filtering, which means that there is almost no noise figure loss from cables or connectors.
Note that the prototype images show an early non-petalized prototype with rough laser cut wind holes. The production version will obviously be a lot neater looking!
In testing the 65 cm diameter Discovery Dish with it's highly optimized feed has proven effective at receiving the GOES HRIT satellite signal with SatDump. We typically achieve SNR values of 3-4 dB to GOES-18 at 24 deg elevation, and with SatDump an SNR of 1 dB is about the minimum required to receive images so there is plenty of margin. It can also easily receive LRIT from GK-2A and Fengyun, and also when combined with an antenna rotator (or manual hand rotating) can receive HRPT weather satellites too.
The feed on the Discovery Dish consists of a tuned dipole feed with two 5V bias tee powered low noise figure LNAs, and two SAW filters (centered at 1680 MHz with 69 MHz Bandwidth). The feeds are also easily swapped out, and we will also be selling a 1.42 GHz Hydrogen Line feed for those who want to use the dish to get started with radio astronomy. Because the LNA's are right by the feed there is are no losses from feed to LNA, so we can use thinner and easier to handle cabling like RG58 without any loss issues.
In the past we've recommended and relied on 60 x 100 cm WiFi dish antennas for L-Band geosynchronous satellites and Hydrogen Line reception, but at 1.6kg these are too heavy, wide and exert too much torque for light duty antenna rotators to handle. At about half the weight of an equivalent WiFi Dish, the Discovery Dish is much easier to handle.
In the future we hope to be able to provide a low cost light duty antenna rotator that compliments the Discovery Dish. Currently we have tested the Discovery Dish with the AntRunner antenna rotator and found it to be light enough for that rotator to handle, versus a WiFi dish which is far too heavy for it.
Also when compared to a WiFi dish, the Discovery Dish is much easier to optimally set the offset skew as you can simply rotate the feed, versus having to rotate the entire dish at 45 degree increments.
We will also be offering an outdoor electronics enclosure that can be used to house a Raspberry Pi, RTL-SDR and other components like POE splitters. In our tests we have been running an RTL-SDR Blog V4, Orange Pi 5 and POE splitter in the enclosure, and running the SatDump GUI directly on the Orange Pi 5. This results in a neat contained system where only one Ethernet cable needs to be run out to the enclosure.
As we are in pre-launch, pricing is not yet confirmed, but we expect the Discovery Dish to sell for less than US$200 with reasonable worldwide shipping costs. It will be a similar cost to what you would pay if you purchased a WiFi dish, filtered LNA and cabling yourself. Obviously please check what satellites can be seen in your region.
SatDump is a popular program that can be used with RTL-SDRs and other software defined radios for decoding images from a wide array of weather imaging (and other) satellites including GOES, GK-2A, NOAA APT, NOAA HRPT, FengYun, Electro-L and Meteor M2 LRPT + HRPT, and many many others. It is multiplatform, running on Windows, MacOS, Linux and even Android. Because of it's good decoding performance, wide satellite and OS compatibility, it is the most recommended software for satellite decoding.
Recently SatDump was updated to version 1.1.0 and the new version brings many enhancements and new features. In summary, Lua scripting support has been added, calibrated products are now possible, composites can be made via Lua scripting, nightly builds are now available on GitHub, Mac .dmg builds are now available, decimation has been added, an SDR Server is available, and a Windows installer was added.
Support for various satellites and their instruments have also been added for NOAA APT, CCSDS LDPC decoding for Orion, LandSat-9, TUBIN X-Band, FengYun-3G/3F, Meteor M2-3, Geonetcast (soon), GOES RAW X-Band, STEREO-A, DSCOVR EPIC, ELEKTRO-L N°4, Inmarsat STD-C, UmKA-1 (soon), PROBA-V GPS .
SatDump also now includes rotor tracking control which works together with it's satellite pass predictor and scheduler. There is no more need to use programs like Orbitron or Gpredict as everything can be handled by SatDump.
An insane amount of work has gone into SatDump, so if you like the software please remember to support the developer @aang23 by donating on Ko-Fi.
Thank you to Carl Reinemann for writing in and sharing with us that the Meteor M2 LRPT decoder by Oleg (Robonuka) was recently updated. The Russian Meteor M2-3 weather satellite was launched in June of this year and is currently the only operational Meteor M2 satellite in the sky. It transmits images at 137 MHz in the digital LRPT format.
To receive it a simple V-Dipole antenna and RTL-SDR is usually sufficient. And to decode it software like SatDump or M2_LRPT_DECODER combined with the Meteor Demodulation Plugin for SDR# can be used. Instructions for the latter are available on HappySats instructional page.
Regarding the update Carl writes:
Thanks to Oleg (Robonuka), Happysat and Usradioguy have been testing the new decoder for about 6 weeks now, and it is ready to go!
The stability of the processing has been improved: The decoder is now more likely to produce stable results, even when there are errors in the input data.
The procedure for generating RGB and calculating GEO in the error-handling block has been improved. Now, the decoder's processing is considered unfinished until the GEO calculation is completed.: This means that the decoder will now wait until the GEO calculation is finished before generating the RGB values. This helps to prevent errors and produce more accurate results.
Exception errors fixed: Some errors that were previously causing the decoder to crash have been fixed.
AutoClose=yes by default: This means that the decoder will now automatically close when it is finished decoding. This can be helpful for saving resources and preventing memory leaks.
80K is much more stable: The decoder is now more stable than before. This means that it is less likely to crash or produce unexpected results.
Overall, these changes make the decoder more reliable and easier to use.
