Tracking Weather Balloons With SDR

The advent of cheap software-defined radio hardware means that what would have once been an exotic expensive undertaking can now be relatively cheap. [David] notes that using some pretty simple gear, he could track down weather balloons.

The U.S. National Weather Service sends up a large number of radiosondes attached to balloons twice a day. Their job is to measure conditions at high altitudes up to about 30km. Once the balloon gets too high, the pressure inside bursts the balloon, and a small parachute slows the instrument package’s descent back to Earth. [David] wanted to track these down and return them to the NWS for reuse.

There are several interesting items to note in the post, including a link to a site that tracks ballons all over the world. The radiosondes that [David] wanted to find transmit on 403.4 MHz and they were relatively easy to hear. If you want to join in on the fun, you only need a few simple pieces of gear. One important thing, though, is perhaps the best hack of all: an orange safety vest. As [David] says, “If you’re wearing an orange vest, everyone assumes that whatever you are doing is legit.”

It doesn’t sound like [David] has actually recovered any radiosondes yet. But he found one, but it was, unfortunately, on the other side of a fence with no trespassing signs. We guess an orange vest doesn’t solve all problems.

Of course, some people see the radiosonde hardware as a gift from the heavens but we think it is classier to return them. We’ve actually looked at these devices several times and we always find them fascinating.

26 thoughts on “Tracking Weather Balloons With SDR

  1. This is myth. The hobby electronic magazines had VHF receiver projects, not great, but they were there. Once again, about 1966, a guy in England received weather satellite pictures. In 1971, Paul Wilson described his 2.4GHz converter, which I’m pretty sure he used to receive Apollo transmissions.

    About the mid-seventies there were articles about reeiving weatger satellite pictures, detailed info. Ralph Taggart wrote a book about 1977 on the topic.

    No it wasn’t for everyone, but it was hardly the hardship that kids today imagine

    1. Yes I would agree.
      Once it was a simple affair to construct a receiver with a handful of commonly available components and build a circuit to receive various transmissions. Now you “NEED” an SDR and computer with thousands of transistors and hundreds of hours of programming.

      1. You forgot to mention how expensive and fragile early DRAM (not to say SRAM) was.
        Just look at how many of them are needed for a simple framebuffer device.

        The manual of the clasdic Robot Model 400 SSTV converter will give a clue.

        So unless a storage tube was used that filmed visuals of another CRT, things were very pricey.

        But it wasn’t just price. Early TTL era RAM needed a lot of care. They were prone to static damage, over voltage etc.

        Don’t get me wrong, I’m kind of a fan of vintage tech. But claiming that everything was easier to build or more accessible in the ~1970s is a myth I believe (it was before my time, but my dad experienced that era as a ham).

        Sure, there was surplus stuff to tinket. But some of it was broken or datasheets were unavailable.

        It was a lot of work to get specs. Friends were needed, lots of mails had to be written, parts catalogues must be checked. Which involved traveling to a big library etc.

        And then, the tools.. A simple analogue oscilloscope was a big thing back then. Everyone wanted one due to its usefulness, but maybe wasn’t able to afford one.

        People built simple scopes from scratch or at least tried. It’s no fun if you can’t be certain your tools are working properly.

        And then the adjustment issue. You needed stuff like frequency counters, spectrum monitors, etc. A complete measuring station, so to say. Their functionality wasn’t part of the usual scope yet.

        The poor man’s solution was to use a grid dip meter in most situations, which required much patience.

        1. Everytime SDRs are mentioned here, except when Jenny List writes about internals, it’s always implying that people couldn’t build radios in the old days. But people had no choice, if they wanted to do interesting things.

          But the reality was different. People got by with what they had. They didn’t need all your fancy test equipment. Frequency counters weren’t really a thing until Heathkit had one in 1971, and it was about TTL, lots of repetetive wiring. If you needed to tune something up on an exotic frequency, you’d use a crystal oscillator and multiply it up. To make it sound difficult or impossible is to deny the long history of radio experimentation.

          I wasn’t talking about receiving satellite photos. But here’s some real history. Copthorne McDonald started writing about SSTV in 1958. It wss based on cheap surplus long persistence display tubes. For a decade, you had to build. There was even a project in 1970 for turning an oscilloscope into an SSTV monitor by swapping the CRT to a P7 tube. Yes, about 1973 or 74 there were scan converters, but they used NMOS memory, I recall long shift registers. But it was surplus, and supplies would run out.l

          SSTV was the foundation of much of the weather satelite reception. Ralph Taggart cowrote a book about SSTV in 1972, and then got interested in weather satellites. So people built, though I think some tried using surplus fax machines.

          But I was talking about the radio hardware. People lived without SDRs.

          1. Alright, but no need to teach me.
            I’ve got some of the old stuff laying around right here (FT-101, Robot 400, Trio 9R59DS, SSTV camera/monitor with 7s afterglow etc), including the matching OM. He’s NOS, hi. :)

            Seriously, though. For adjustment, say of an 1960s Yaesu FL 200 transmitter (all tube), a frequency counter, a wobbler, dip meter, a scope etc. is highly recommended. Without proper tools, you’re at construction kit level.

            A scope, an ampere/volt meter and a dip meter was the base line level. Plus a jigsaw, a toolbox with some screw drivers.. Maybe optionally some function generator, a little RF signal generator (even if was just fixed frequency/crystal controlled).

            I assume that’s what most hams had which were into DIY or small/medium repair jobs.

            But if you’re referring to building a regenerative receiver (“Audion”), a crystal-controlled CW transmitter or a foxhole radio / a crystal radio, then sure, these things aren’t needed.

            CW can also be done by adjusting the level of the feedback of the Audion / Regenerative Receiver.
            At some point, the oscillation travels back to the antenna and you’ve got a weak transmitter.

            Best wishes, vy55/73,

          2. I see whete you’re coming from and I understand what you mean to say, but personally, I’m overly joyful and glad that hams moved beyond the dreadful superhet.

            The superhet was a good idea, in somewhen in the 60s, sure.
            But it became a dead end, also.
            Single-super, double-super, tripple-super etc.
            Until the self-noise of the transistors made the receiver insensitive to weak signals. What a stupidity.

            But radio amateurs were unable to evolve beyond it. They compensated with more and more filtering. Ever increasing complexity vs elegance.. Until the SDR principle came around.

            People looked back to the roots and recognized, that a simple direct-conversion (DC) receiver and a computer with a soundcard could do much better.

            That’s when amateur radio finally (🙏) moved on. SDRs gave new life to the hobby/service.

            The SDyr movement also saved old equipment. Many OMs nowadays use SDRs with their belovec old receivers. They add an IF out to their vintage radios and use SDRs as monitor scopes/panorama adapters. Back in the 1970s, these costed more than the radio, sometimes!

            The bottom line is:
            Old and new are no contradiction.
            Tube technology could be paired excellently with modern SDR technology. Tubes are wonderful as RF fronteds and amps.

            Just have a look at this schematic.
            SDRadio or DREAM can demodulate.

            The SAQ software SAQrx can work with a soundcard alone (+antenna), even. The 17,2 KHz signal from Grimeton can be received with an 48 KHz soundcard.

          3. Interesting tidbit… the first video image transmitted to, and received by the Space Shuttle used SSTV. The crew got to watch images of their own launch. This was part of the Shuttle Amateur Radio EXperiment (SAREX), which was the predecessor to Amateur Radio on International Space Station. Later, the first fast-scan (NTSC) TV images sent to and received by a Shuttle crew were made to happen by the SAREX team again.

        1. SDRs can do Synchronous Detection for AM, also.

          AM (Sync) was never really cared about by amateurs, which is a shame.
          It’s much more pleasant to listen to, than say, SSB. Hi.

          Gratefully, SDR software can decode/demodulate AM this way.
          – The WebSDR has a separate radio button (pun intended) for it.

          Receivers in avionics have that feature, too, I vaguely remember.

  2. Why is it “classier to return them”? The Radiosonde devices are not reusable, the weather services that launch them consider them single use items, and they get all the data they need from them while in flight… So, why return them when they will just throw them in the trash anyway?

      1. Notice it says “If the NWS radiosonde comes with a postage paid mailbag…” then it could be returned and possibly re-used. The vast majority of the ones flown in the US are Vaisala Radiosonde RS41, the 3rd image on the right, and they have a label stating “Please do not return the radiosonde to the NWS.”

  3. I found a radiosonde in my backyard in the early 90’s. I took it apart as much as I could without destroying it, put it back together and then mailed it back. I had it in the house for a little while but my mother put it outside because it smelled strongly of ozone.

  4. Hunting radiosondes is a lot like geocaching on steroids! Plus adding custom firmware on these devices is a lot of fun.
    I’m happy to see more people talking about these on the media, we could always use more people the the community.

    1. If I tell my coworkers I’m hunting weather balloons, they think I’m just a weirdo… but if I explain it as “Geocaches from the sky” it seems to be more understandable. I think it’s an awesome excuse to ride my motorcycle out into the middle of nowhere, so I’ve been enjoying it.

      1. Cool, here in Germany, we do the same.

        The radio sondes are used as disposable products.
        While they could be used multiple times technically, the weather people decide to don’t do this.

        Maybe because they want to be sure correct information is gathered and so there’s that fear an used probe might be having too much wear.

        But it’s important that if we collect the probe, that we collect everything.

        Only this way, we do properly contribute something (clean the landing site):

        Getting the sonde, but Leaving the strings and the balloon behind is not good practice.

        Animals or children could get hurt if they get entangled with them.

  5. Just an overall comment. I am 81 years old and it is wonderful to see the spirit of todays ‘hackers’. When I was 15, I bought my first Mullard Transistor, the OC71. I started to build single transistor circuits from the electronic magazines of the day. Then I read an article that described how to scrape the paint off the OC71 to make a light sensitive device. My first circuit was the scraped OC71 transistor and a relay to turn on our house front lights when it got dark. It worked great until my mother asked, why are the lights on during the day, oops! A quick wiring change corrected that.
    Anyway Mullard cottoned onto what the ‘hackers’ of the day were doing and then advertised their new product: the ‘OCP71’ and sent several OCP71 transistors to a whole bunch of electronics hobbyists (the term electronics Hacker was not known in 1957).
    So it it amazing to see what is happening today when we treat a complete processor as a ‘component’.
    And, yes I do have a whole box of early and recent processor boards/modules. Keep up the good work, take us to Staurn or Uranus on your experimentation.
    Adrian Zeffert (60 years of systems engineering).

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