Tagged: discovery dish

Tech Minds: Testing out Discovery Dish for Inmarsat and Hydrogen Line Radio Astronomy

Over on YouTube Matt from the Tech Minds YouTube channel has recently uploaded a new video where he tests out our Discovery Dish antenna. Discovery Dish is designed to be a low-cost, portable solution for receiving L-band and S-band weather satellites, Inmarsat satellites, conducting amateur hydrogen line radio astronomy, and more.

In the video, Matt unboxes the Discovery Dish and provides an overview of the build process before demonstrating its use in decoding AERO and STD-C messages on Inmarsat. He then shows the dish and Inmarsat feed being used to receive Iridium satellites, and how they can be decoded using iridium-extractor with a HackRF or Airspy R2.

Finally, Matt swaps out the Inmarsat feed for the Hydrogen Line feed. Using SDR#, the IF AVG plugin, and Stellarium, he was able to obtain a clear hydrogen line peak.

This Discovery Dish Is The ONLY Satellite Dish You Will Need!

Discovery Drive: An Affordable Antenna Rotator Crowd Funding Pre-Launch Page now Active!

We're happy to announce that the pre-launch page for our "Discovery Drive" automatic antenna rotator is now live! Please sign up to be notified of when the crowdfunding page goes live as the price will be reduced by at least $100 during the campaign.

Discovery Drive is an automatic antenna rotator that is designed to be used with our Discovery Dish product, as well as similarly sized antennas such as Wi-Fi grid and Yagi antennas.

Discovery Drive with Discovery Dish Mounted
Discovery Drive with Discovery Dish Mounted

A motorized rotator allows you to use a satellite dish or directional antenna to track and receive signals from polar orbiting satellites, which quickly move across the sky. It also lets you switch swiftly between geostationary satellites without manually realigning the dish. 

Examples of polar-orbiting weather satellites that you can track include NOAA POES, METEOR-M2, METOP, and FENGYUN. Depending on your location, you may also have access to other interesting satellites that dump data over specific regions. Amateur radio operators can also use Discovery Drive to track amateur radio satellites with Yagi antennas.

Discovery Drive
Discovery Drive

Discovery Dish is designed to be easy to set up and use. Unlike many other rotators on the market, no external controllers are required. Discovery Drive has a built-in ESP32 controller, and control can be commanded over WiFi or serial from rotctl-compatible software such as SatDump, GPredict, and Look4Sat on Android. 

Features and Specifications

  • Up to 125 kgcm (12.25 Nm) of torque
  • ESP32 control board
  • ± 1.5° of accuracy
  • -360° to +360° Azimuth range, 0° - 90° elevation range
  • 1.5 RPM Azimuth speed, 0.25 RPM elevation speed
  • 12 V power input (either barrel jack or USB Type-C Power Delivery)
  • Wi-Fi connectivity with browser-based web UI
  • Serial over USB data connectivity or Wi-Fi data connectivity
  • Low power draw (< 10 W, can be powered with PoE+ supplies and still have power left over for powering a single board computer and RTL-SDR)
  • Robust worm gear-locked output drives
  • Direct rotctl compatibility over Wi-Fi (compatible with programs that implement the rotctl protocol, such as SatDump, GPredict, and Look4Sat on Android)
  • Hamlib compatibility (EasyComm II protocol)
  • Waterproof outdoor enclosure
  • Open source ESP32 firmware 
Discovery Drive Inside Look
Discovery Drive Inside Look

IEEE Spectrum Article on Discovery Dish

Electrical engineering magazine IEEE Spectrum has recently posted an article about our Discovery Dish product, which was successfully crowd-funded on CrowdSupply and delivered to initial backers early this year. Discovery Dish is a 70-cm aluminum satellite dish with an active filtered feed. It is designed for receiving real-time weather data from GOES HRIT, GK-2A LRIT, FengYun LRIT, NOAA HRPT, Metop HRPT, Meteor M2 HRPT, and other weather satellites that operate around 1.69 GHz. There are also feeds for Inmarsat satellites, Hydroden Line observation, and S-band satellites.

In the article, Stephen Cass introduces the Discovery Dish, highlighting its practical uses and the convenience of disassembling it for easy packing in a suitcase during travel. He also shares his experience using the Discovery Dish to successfully receive images from the GOES-East satellite from the rooftop of his New York City apartment.

Finally, he mentions how he tested the hydrogen line feed as well, successfully seeing a hydrogen line peak when pointing at the galaxy.

Image from the IEEE Spectrum Article on Discovery Dish
Image from the IEEE Spectrum Article on Discovery Dish

A Review of the Discovery Dish for Inmarsat Reception

Over on the Airframes Community forum, user 'thebaldgeek' has posted a review of our Discovery Dish product. If you weren't already aware, the Discovery Dish is an easy-to-set-up and use backyard dish system for weather satellites, Inmarsat, and Hydrogen line radio astronomy.

In his post, thebaldgeek unboxes the dish and feed boxes, showing all the individual parts. He goes on to bolt the dish together and show it fully built. In the rest of the post, he compares the Discovery Dish with Inmarsat feed against three other options, including a GPS puck, our RTL-SDR Blog Active Patch Antenna, and a homemade 7-turn helix antenna.

As expected, the Discovery Dish performs the best, with the 7-turn helix coming in second, followed by the RTL-SDR Blog Patch, and finally, the GPS patch. He rightly notes that the dish does have increased wind loading over the other options, and this needs to be taken into account when positioning and mounting.

Inmarsat antennas tested by 'thebaldgeek'.
Inmarsat antennas tested by 'thebaldgeek'.

Saveitforparts Checks out the Discovery Dish

Over on his YouTube channel 'saveitforparts,' Gabe has uploaded a video checking out and reviewing our Discovery Dish product that we successfully crowd-funded on CrowdSupply back in December 2023.

Discovery Dish is designed as a low-cost way to dive straight into backyard satellite experiments, including receiving L-band and S-Band weather satellites as well as Inmarsat satellites. It also offers an easy entry into making galactic Hydrogen line observations.

The dish is a 70cm prime focus dish, that can easily be broken down into three parts for easy storage and transport. The feeds are fully integrated, meaning that the feed antenna, LNA, and filtering are all in one unit and built into a waterproof enclosure. This means there is no need to purchase individual components and figure out waterproofing.

In his video, Gabe unboxes the Discovery Dish, builds it, and uses the L-band feed to receive a few images from GOES 16, Meteor M3, Meteor M4, and METOP weather satellites. He goes on to successfully test reception with the S-band feeds on NOAA weather satellites, before testing out the Inmarsat feed and successfully receiving signals. Finally, Gave notes that he hopes to test out the Hydrogen Line feed in a future video.

Checking Out The Discovery Dish - A Simple & Easy-To-Use Satellite Antenna For Everyone!

Discovery Dish April Manufacturing Update

This was posted over on our Discovery Dish Crowd Supply updates page and we are cross-posting here too.

It’s been over a month since our last update so we thought we’d share some of the recent progress. As mentioned in our last update, during the month of February all manufacturing was shut down due to the Chinese New Year holiday. In early March, staff returned to the factories and began making progress on finishing Discovery Dish.

We have a snazzy new logo, and we are working on obtaining some stickers to include with the feeds.

 

Dish Manufacturing Progress

The molds for the dish stamping machine were successfully created in March and the test stamps have come out great. The manufacturer is still tweaking the secondary mold that stamps the mounting and connecting holes, but we expect that to be completed shortly. Once that is done and tested, we can begin stamping the dish segments en masse.

The Dish mounting system was also finalized and we added 45-degree markers to it, which can help with aligning skew.

We are still awaiting the results of the anodizing tests, but they should be completed by the end of this month. Anodizing the dish is important as the dish must be a dark non-reflective matte color, so that it does not focus hot sunlight onto the feed point plastic head.

Feed Manufacturing Progress

PCB Upgrades

While waiting for the manufacturers to finish up with the molds, we’ve been further refining the PCB feed. Our final version of the PCB has now moved to a PTFE substrate with significantly lower loss at higher frequencies. This has yielded an over 1 dB increase in SNR at the GOES 1.69 MHz frequency.

The change to PTFE was not without problems. An interesting RF engineering problem occurred with the move to PTFE that we wanted to share. When moving to PTFE the only changes to the board layout are PCB trace width changes to keep the impedances matched. Other than that, the boards and layout are essentially identical. However, we discovered that the dual LNA design started oscillating when we moved the PTFE substrate. Oscillations can occur with LNAs when RF essentially bounces back and forth between the two LNAs, which causes undefined behavior in the LNA, such as poor gain, multiple spikes in the spectrum, and unexpected current draw values.

We found this quite odd because oscillations were not occurring in the original FR4 PCB, and the QPL9547 LNA is advertised as ‘unconditionally stable’ which means that it should never oscillate. However, we found that unconditionally stable guarantees may not apply to two-stage designs. In the end, the fix was simple, we just needed to add a damping resistor to one of the inductors on the circuit which reduces its Q-value. It seems that the change from FR4 to PTFE effectively increased the Q-value of this inductor so much, which in turn induced an oscillation in the circuit.

Discovery Dish Feed Head Enclosure

We’ve also refined the entire feed assembly. The feed arm pipe now has a ruler laser etched onto it so that mounting it at the correct distance is easy. A skew angle guide has also been added around the neck. A thumbscrew locking mechanism has been added to the feed head neck too, so that skew can easily be adjusted without the need for a screw driver or Allen wrench to loosen the set screw.

The PCB enclosure has been slightly refined and the injection molding die is currently in production and due to be completed in mid-May. While waiting for the die to be made, we’ve been testing different plastic mixes for the head enclosure to make sure that they are UV stable. The plastic mix has certain strict requirements and choosing the correct mix is crucial. It has to be RF-transparent with a low relative permittivity value, it has to endure direct sun, UV damage, and freezing weather, as well as be water-proof too.

S-Band Feed

Previously as noted in prior updates we were testing an S-band feed with the FR4 substrate. But we found that there was too much loss and the SNR values we got were not great. The move to PTFE substrate means that our experimental S-band feed is now working very well. We will be releasing this in the near future as an additional feed product that can be used with Discovery Dish. This feed will have a frequency range of 2.2 GHz - 2.3 GHz. This covers the main S-band weather satellites, other satellites like Coriolios and JASON as well as the many dump-only S-band satellites that transmit signals only over certain regions.

As requested by most people interested in an S-band feed, the S-band feed will not include a downconverter, so to use it you will either need an SDR like the HackRF which is capable of tuning to the S-band, or a third-party downconverter product.

Discovery Dish Outdoor Metal Enclosure Progress

Our enclosure set is now complete, and the final packing has almost been completed. The user manual can be found here Discovery Dish Outdoor Enclosure User Manual.pdf.

The final set consists of:

  • 1x Metal Enclosure
  • 3x Custom metal cable glands
  • 1x Vent
  • 1x Electronics mounting board
  • 1x Pole mounting set (with hose clamps)
  • 1x Wall/DIN mounting set
  • 1x 10 mm x 10 mm x 8 mm thermal pad (to be placed under the electronics mounting board)
  • 1x 10 mm x 10 mm x 3 mm thermal pad (to be placed under electronics on top of the mounting board)
  • 1x Set of various screws and washers

(Note that there will be some minor changes from this image in sets going out of customers - the hose clamp will be shorter, and the mounting rails will be longer)

Meteor M2-4 Launch

We mentioned in our last update that a new weather satellite Meteor M2-4 was due to launch. The launch was successful and the satellite is now in orbit. The satellite was briefly turned on after launch, and we were able to receive HRPT images from it in the L-band. However, now it is currently in a testing phase so the transmitters are often turned off. We don’t know how much longer it will be in testing, but we assume it won’t be more than a few more months.

GOES-U / GOES-19 Launch Updates

We’ve been keeping an eye on the expected launch date for the next GOES satellite. Currently, it has been delayed from April 30, 2024, to the new date of June 25, 2024, when it will be launched on a Falcon Heavy from Kennedy Space Center, Florida.

Elektro-L4 Updates

In the last update, we mentioned that we were having some problems getting SatDump to receive Elektro L4 properly on computing devices that used ARM processors. After some investigation, we determined that this was a problem with buffer size settings in SatDump and we were able to suggest a fix in https://github.com/SatDump/SatDump/pull/616 which was implemented. New versions of SatDump have this problem fixed.

Driver Tweaks

We have been looking at the RTL-SDR drivers and have found a few tweaks that can improve performance at L-band frequencies. We’ve put a modified version of the librtlsdr/librtlsdr fork up our the rtlsdrblog GitHub at https://github.com/rtlsdrblog/librtlsdr. With this fork and the PTFE feed upgrades, we now get around 5-6 dB of SNR on GOES-18.

Antenna Rotator

The low-cost antenna rotator is finishing up with prototype testing, and we are now working on improving the design’s manufacturability.

Timeline

The ramping of progress from the Chinese New Year holidays to now has been a little slower than expected, but if everything goes perfectly to plan, we will be on time for shipping by the end of June. However, this is currently a best-case scenario. There are still a few manufacturing stages to get through like the final mass production, CE testing and sea freight shipping. Unfortunately, from prior manufacturing experience, there are always setbacks along the way that slow progress, so we are conservatively pushing our advertised timeline back by about 1-2 months. We apologize for any potential delays, but we are working hard to get the product out to you ASAP!

Customer Questions

We have had a few more customer questions over email which we’d like the answer publicly below:

Would it be practical to use this kit indoors to do hydrogen-line astronomy? I ask because I live in a flat in a block of retirement flats, and wouldn’t be able to place an aerial or dish outside, but could find space for a Discovery dish + rotation gear inside.

Unfortunately, indoor Hydrogen line astronomy is out of the question. The hydrogen line signal is just too weak to be seen indoors, and there would most likely be too much interference indoors as well.

What all do i need to purchase and get for the Discovery Dish for Radio Astronomy?

You’ll need these two components from the Discovery Dish Crowd Supply store:

  • Discovery Dish (Dish & Mount Only)
  • Hydrogen Line Discovery Feed

You will also need a software defined radio, such as an RTL-SDR Blog V3/V4 which can be purchased separately, a computer and somewhere to mount your dish (e.g. a mast/tripod etc).

Have you tested this for C-Band / Aero downlink reception?

Currently, we do not have a C-band feed, so we have not tested it for this purpose. Generally, a larger 1.2 m+ dish is required for C-band AERO, so the 70 cm Discovery Dish may not be suitable. We may test this with Discovery Dish in the near future just in case however.

I want to purchase a hydrogen antenna. Where should I buy it? Also, please tell me what is needed to observe seti radio waves.

The Discovery Dish (Dish & Mount) and Hydrogen Line Discovery Feed can be pre-ordered from the Discovery Dish Crowd Supply store. I’m not sure exactly what you are referring to with SETI radio waves. An alien signal could in theory be on any frequency, but the 1.42 GHz Hydrogen line frequency could be a good bet as it’s a universal frequency of interest that any technological civilization would be observing. Realistically the Discovery Dish would be too small to detect potential alien signals unless they were very strong.

I’ve seen a small home made 3D-printed dish called a ‘heliocone dish’ being used for HRPT. How is Discovery Dish different?

The heliocone 3D printer design going around is a great DIY solution for L-Band polar orbiting HRPT satellites. But it has some limitations as it cannot receive the weaker geostationary satellites due to its smaller size and use of a circular polarized feed. It also cannot receive satellites using the opposite circular polarization. It also cannot receive satellites on different frequencies or the Hydrogen Line without designing a new helical feed and using a different LNA+filter combo. Discovery Dish is a more of a general purpose ‘does-it-all’ and ‘ready to use’ out-of-the-box dish. With our dish and feeds you can receive the L-Band polar orbiting HRPT satellites as well as the geostationary satellites. You can quickly swap out the feed for a different feed that covers a different band as well.

 

Multiple Comprehensive Tutorials on Weather Satellite Decoding

Over on his website "Jacopo's Lair" IU1QPR (@original_lego11) who is also a developer for SatDump has written up many tutorials about weather satellite decoding that involve the use of SatDump. SatDump is a popular piece of software often used with RTL-SDRs and other low cost SDRs for decoding weather satellite images.

With a small satellite dish, feed, RTL-SDR and LNA+filter and the SatDump software it's possible and download beautiful images of the earth from many geostationary and polar orbiting weather satellites. We note that we are currently taking pre-orders on Crowd Supply for our Discovery Dish system, which is low cost hardware designed to help users get started with weather satellite reception.

Over on Reddit IU1QPR has created a listed summary of all the tutorials he's written. These are currently the most up to date and comprehensive tutorials that we have found on this topic. The tutorials cover everything from what satellites are available, what dish sizes you need, what SDRs can be used, what LNA+filter and other hardware you need, and how to use the SatDump software.

Satellite reception and decoding

Automated stations

SatDump usage

All have been moved to SatDump's documentation page

Satellite data processing and usage

From the HRPT tutorial: What various HRPT signals look like on the spectrum.
From IU1QPR's HRPT tutorial: What various HRPT signals look like on the spectrum.

The Biggest RTL-SDR and Related Stories from 2023

This year there were several interesting stories and product releases that we posted about on the blog and this post will be a brief end of year review of some of our most popular posts. We also wanted to wish everyone a Merry Christmas and Happy Holidays to every celebrating at this time of the year!

In January we saw that the popular ADS-B Exchange (ADSBx) ADS-B aggregation platform was sold to a private equity firm called JETNET. This caused quite a bit of outrage as many involved with the development of the platform were blindsided by the owner's sudden decision to sell. ADS-B Exchange is a popular ADS-B aggregator that uses RTL-SDRs and is known for it's hard no censorship policy, allowing it to be used in projects like "Dictator Alert" and to uncover immoral use of aircraft in policing and military "kill chains". Many of the original team have since started a new service at https://airplanes.live.

ADSBExchange.com interface
ADSBExchange.com interface

Next in February at the height of the "Chinese Spy Balloon" scare we ran a story about how the US air force had shot down an amateur radio 'pico balloon' called K9YO-15  , on the assumption that it could have been another Chinese spy balloon. Pico balloons are party sized helium balloons with a solar powered amateur radio transmitter attached. The fun of the hobby is seeing how far and long around the world they can travel for. A typical pico balloon could circumnavigate the globe several times over several months, all whilst transmitting it's position.

Rough trajectory overlay
Rough trajectory overlay

In April we saw the Flipper Zero go mainstream when it was reviewed on the Linus Tech Tips YouTube channel. The Flipper Zero is a small RF hacking device that gained high popularity on social media sites like TikTok. 

Linus Tech Tips Reviews the Flipper Zero
Linus Tech Tips Reviews the Flipper Zero

In June we saw a video from a YouTuber that appeared to show a Flipper Zero being used to wirelessly 'let the smoke out' and self-destruct an electricity meter which raised major infrastructure security concerns. However, this video appears to have since been removed, and there was speculation that the video was faked, or at least staged in some way.

In July we showed a video demonstration of how our KrakenSDR could be used to track down a low power FM transmitter station. In August we showed the KrakenSDR tracking down multiple GSM base station transmit towers simultaneously.

Later in August we also released the RTL-SDR Blog V4 dongle, a limited edition RTL-SDR that makes use of existing stockpiles of R828D tuner chips. It has improved HF performance thanks to an upconverter, and improved filtering on the VHF and UHF bands.

In September we saw crowd funding start for the RFNM, a device that promises to be a next generation software defined radio.

Finally in November we saw the release of the crowd funding campaign for our Discovery Dish project, a low cost and easy way to get into reception of L-band satellites, as well as Hydrogen Line radio astronomy.

Later in November we also saw a great technical overview of the Watch Duty wildfire monitoring project which uses multiple RTL-SDRs in their system.

The Discovery Dish
The Discovery Dish