The U.S. government recommends that everyone have a disaster kit that includes a weather radio. These radios tune to a nationwide network run by the National Oceanic and Atmospheric Administration (NOAA) and the Federal Communications Commission that provides alerts about hazardous weather and other major emergencies. Such broadcasts can be a lifeline when other communication systems go out. But what if you could step it up and get not just audio information but also images, charts, and written reports, even while completely off the grid?
Turns out you can, thanks to modern geosynchronous weather satellites, and it’s never been easier than with KrakenRF’s new Discovery Dish system. This system involves buying a US $115 70-centimeter-diameter parabolic antenna, and then one of a number of $109 swappable feeds that cover different frequency bands. To try out the system, I got one feed suitable for picking up L-band satellite transmissions, and another tuned for detecting the radio emissions from galactic hydrogen clouds.
The parabolic antenna comes as three metal petals plus some ancillary bits and pieces for holding the feed and mounting the dish on a support. Everything is held together with nuts and bolts, so it can be dissembled and reassembled, and the petals are light and stack together nicely—you could pack them in a suitcase if you ever wanted to travel and sample a different sky.
In addition to KrakenRF’s dish and feed, you’ll also need a software-defined radio (SDR) receiver and a computer with software to decode the signals coming from the feed. Many SDRs can be used, but you’ll need one that comes with what’s known as a bias tee built in, or you’ll need to add a bias tee yourself. The bias tee supplies power to the low-noise amplifiers used in KrakenRF’s feeds. I used the recommended $34 RTL-SDR Blog V3 (which comes as a USB dongle), with my MacBook, but you can use a PC or Raspberry Pi as a host computer as well.
After I inserted the L-band feed into the dish, it was time to look for a satellite. Following KrakenRF’s guide, I used Carl Reinemann’s Web app to print out a list of azimuths and elevations for geosynchronous weather satellites based on my location. Then I headed up to the roof of my New York City apartment building with the mast from my portable ham radio antenna to provide a mount. And then I headed straight back down again when I realized that it was too blustery for a temporary mount. The dish is perforated with holes to reduce air resistance, but there was still a real risk of the wind toppling the portable mast and sweeping it over the side of the building.
A couple of days later, I returned to calmer conditions, and with my iPhone employed as a compass and inclinometer, I pointed the dish at the coordinates for the GOES-East weather satellite. This satellite hangs over the equator at a longitude of 75 degrees west, close to that of New York City. A second satellite, GOES-West, sits at 135 degrees west, over the Pacific Ocean.
These GOES satellites are fourth-generation spacecraft in a long line of invaluable weather satellites that have been operated by NOAA and the U.S. National Weather Service for 50 years. The first of the current generation, known as GOES-R, launched in 2016 and features a number of upgrades. For radio enthusiasts, the most significant of the upgrades are its downlink broadcast capabilities.
The current GOES satellites transmit images taken in multiple wavelengths and scales. A false-color full-disk image [above] is captured in an infrared band that detects moisture and ash; the image at top shows the eastern United States in an approximation of what you would see with the naked eye. Stephen Cass/NOAA
The GOES-R satellites transmit data at 400 kilobits per second, versus a maximum of 128 Kb/s for previous generations, allowing more information to be included, such as images from other weather satellites around the globe. The satellites also merge satellite-image data and emergency and weather information into a single link that can be simultaneously picked up by one receiver, instead of needing two as previously.
For fine dish-pointing adjustments, I was guided by watching the signal in the frequency spectrum analyzer built into SatDump, an open-software package designed for decoding satellite transmissions picked up by SDR receivers. I groaned when no matter how I adjusted the dish, I could barely get the signal above the noise. But much to my surprise, I nonetheless started seeing an image of the Earth begin to form on the display.
The original GOES-R design specified that receiving ground dishes would have to be at least one meter in diameter, but the folks at KrakenRF have built their feeds around a new ultralow-noise amplifier that can make the weaker signal gathered by their smaller dish usable. Soon I had pictures of the Earth in multiple wavelengths, both raw and in false color, with and without the superimposed outlines of states and countries, plus a wide assortment of other charts plotting rainfall and wind speeds for different areas.
The GOES satellites also broadcast information uploaded from the U.S. National Weather Service, such as this chart of marine wind speeds.Stephen Cass/National Weather Service
My next test was to do a spot of radio astronomy, swapping out the L-band feed for the galactic hydrogen emission feed. Getting results was a much longer process: First I had to point the dish at a bit of the sky where I knew the Milky Waywasn’t to obtain baseline data (done with the help of the Stellarium astronomy site). Then I pointed the dish straight up and waited for the rotation of the Earth to bring the Milky Way into view. Pulling the signal out of the noise is a slow process—you have to integrate 5 minutes of data from the receiver—but eventually a nice curve formed that indicated I was still safely within the embrace of the spiral arms of our home galaxy. Much more sophisticated radio astronomy can be done, especially if you mount the dish on a scanning platform to generate 2D maps. But I swapped back the L-band feed just to marvel at how our planet looks from 36,000 kilometers away!
