Category: Discovery Dish

Measuring Antenna Gain Patterns with Discovery Drive

Our Discovery Drive campaign is currently being crowd-funded on Crowd Supply. Please consider ordering a unit if you are interested in a high-quality, low-power, and portable antenna rotator. Below is an update from the campaign exploring a potential use-case for measuring antenna gain patterns:

In this update, we’ll examine an alternative use case: measuring antenna gain radiation patterns.

One interesting use of a capable Az/El rotator is to measure the radiation pattern of various antennas. This is normally done in an anechoic chamber, but if you have a large enough open space, it can be done cheaply with a rotator and signal source.

To test this as a proof of concept, we used Claude code to very quickly create a tool that could help us create an antenna pattern plot. The software tool simply rotates the antenna on the Discovery Drive one step at a time, measures the SNR using an RTL-SDR, and plots the reading on a graph. To be clear, this simple setup is not providing any sort of calibrated readings, but it will at least give you an idea of what the radiation pattern and performance of an antenna looks like.

In our test, we mounted a TV Yagi on the Discovery Drive and used our software to plot the radiation pattern at 433 MHz. As expected from a Yagi, we see higher gain at the front and lower gain at the rear.

Antenna Gain Results
Antenna Gain Results

Due to a lack of a suitable open area, this test was performed in a small backyard and, hence, the radiation pattern is a little lopsided due to multipath. In this test, we also used a simple omnidirectional antenna for the signal source, which exacerbated the multipath. A way to improve this test would be to use a directional antenna on the transmit side, too.

We will release this open-source tool for others to play with, but please be aware that it was only created for proof of concept. However, if there is interest, we can continue to refine it.

Below is a photo of the physical setup. A HackRF with Portapack and whip antenna are mounted on a tripod a few meters away, while the Discovery Drive carries a Yagi antenna. As the Discovery Drive rotates the Yagi through 0 to 360° in azimuth and -30 to 90° in elevation, it measures the received power at each step.

Antenna Gain Measurement Backyard Setup
Antenna Gain Measurement Backyard Setup

Saveitforparts: Testing a Prototype Discovery Drive Az/El Antenna Rotator

Over on YouTube, Gabe from the saveitforparts channel has uploaded a new video testing a prototype of our upcoming Discovery Drive Az/El antenna rotator, which is now live for crowdfunding on Crowd Supply.

In the video, Gabe unboxes the Discovery Drive and sets it up with a Discovery Dish. He then tests it on various weather satellites, including Meteor M2-4, Meteor M2-3, DMSP, Metop-B, and Metop-C.  Later in the video, Gabe shows that you can also attach an Arrow Yagi antenna to the mount and notes that in a future video, he hopes to test CubeSat and Amateur radio satellite reception with the Yagi.

Testing Prototype Discovery Drive Satellite Tracker

Discovery Dish 1420 MHz Hydrogen Line Feed Tested with a WiFi Grid Dish

Thank you to Alex P for writing in and sharing with us his detailed evaluation of the Discovery Dish 1420 MHz hydrogen line feed when paired with a low-cost 1m WiFi grid dish. The goal was to see how well this near off-the-shelf setup performs as a hydrogen line radio telescope. The Discovery Dish feed integrates the dipole very close to the internal LNA and filters to minimize losses, uses a weather-sealed enclosure, and is built around a low-noise Qorvo QPL9547 amplifier, which has a very low noise figure at 1420 MHz.

Alex used 4NEC2 with a simple geometry approximation to analyze the beam pattern and also experimentally determined the optimal feed-to-dish spacing for the WiFi grid. The results show that the Discovery Dish feed significantly outperformed a more standard feed + external LNA setup.

Alex also shows how he uses aluminum foil, or conductive foam, to shield the feed from all signals during a background correction scan. Generally, for background correction scans, we recommend pointing towards a cold area of the sky (any area far away from the Milky Way with little to no hydrogen), but Alex prefers this method.

Discovery Dish 1420 MHz Hydrogen Line Feed Tested on a WiFi Grid Dish
Discovery Dish 1420 MHz Hydrogen Line Feed Tested on a WiFi Grid Dish

WOW@Home: A Global Network of RTL-SDR Based Radio Telescopes Looking for Alien Technosignatures

The Wow! signal is a famous, strong, and unexplained radio signal detected in 1977 by the Big Ear radio telescope in Ohio, lasting 72 seconds and appearing to originate from the constellation Sagittarius. Its origin remains unknown, with some speculating that it could be an extraterrestrial technosignature. Upon reviewing the signal data, Astronomer Jerry R. Ehman discovered the powerful signal burst in the readout and wrote a large "Wow!" next to it, unintentionally coining the name.

Wow@Home is a new project that aims to coordinate a network of small radio telescopes globally, in the hopes of increasing our chances of detecting interesting astrophysical and technosignature events, such as the Wow! event.

A network of small radio telescopes offers several distinct advantages compared to large professional observatories. These systems are low-cost and can operate autonomously around the clock, making them ideal for continuous monitoring of transient events or long-duration signals that professional telescopes cannot commit to observing full-time.

Their geographic distribution enables global sky coverage and coordinated observations across different time zones, which is especially valuable for validating repeating or time-variable signals. Coincidence detection across multiple stations helps reject local radio frequency interference (RFI), increasing confidence in true astrophysical or technosignature transient events.

These networks are also highly scalable, resilient to single-point failures, and capable of rapid response to external alerts. Furthermore, they are cost-effective, engaging, and accessible, ideal for education, citizen science, and expanding participation in radio astronomy.

However, these systems also come with notable limitations when compared to professional telescopes. They have significantly lower sensitivity, limiting their ability to detect faint or distant sources. Their angular resolution is poor due to smaller dish sizes and wide beamwidths, making precise source localization difficult.

Calibration can be inconsistent across stations, and frequency stability or dynamic range may not match the performance of professional-grade equipment. Additionally, without standardized equipment and protocols, data quality and interoperability can vary across the network.

Despite these constraints, when thoughtfully coordinated, such networks can provide valuable complementary observations to professional facilities.

The team note that the Wow! signal was strong enough that it could have been detected by a small home radio telescope. They go on to make the case that we could be missing out on detecting many compelling signals simply because radio telescopes aren't watching every part of the sky simultaneously. 

The project will monitor the Hydrogen Line frequency for interesting signals. Currently, the team is using a WiFi grid dish and an external LNA as the radio telescope hardware, but they also aim to evaluate our Discovery Dish with H-Line feed.

Wow@Home Typical Radio Telescope Hardware
Wow@Home Typical Radio Telescope Hardware

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'.