9. Two Radiosonde Recoveries in San Francisco

   The prevailing winds here in California blow from west to east, from the Pacific Ocean towards the Sierra Nevada mountains. Radiosondes launched from Oakland International Airport float in these winds, landing east of Oakland in the Central Valley, or south in the hills east of San Jose. I never recover the ones that land in the Central Valley, as driving 2 hours each direction during rush hour to recover a balloon is a bit too far for me. Only rarely do they land in populated areas in the Bay Area, and almost never on the Peninsula or in the city of San Francisco.

   This map (code below) shows the landing locations of all the radiosondes launched from Oakland since November ...

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10. Picoballoon Launch 5

    After the fourth launch, Martin W6MRR respun the tracker board to try and fix some GPS lock errors. Unfortunately, the new layout did not fix the self-interference, but we decided to launch the new tracker board anyways on Saturday May 22nd, 2021. The launch party was Rob NZ6J, Martin W6MRR, Robert K6RGG, and myself KF6ZEO.

    This time, Rob NZ6J brought a 20m receiver and speaker so we could actually verify the tracker was transmitting before letting it float away. While we didn't have any software to actually decode the packets, we were able to see that the transmitter on the radio S-meter. This is more of a nice-to-have, as the tracker board also has an LED that lights up when ...

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11. Picoballoon Launch 4

    The next Saturday after the third launch, Martin W6MRR, Robert K6RGG, and Rob NZ6J got together at the Berkeley Marina and launched another picoballoon. I was away on a much-needed vacation.

    Since the last launch didn't get above 9000 meters, Martin spent extra time measuring the payload and lift of the balloon. To go around the world, it's important that the balloon has enough lift to rise above weather that may push the balloon down, or coat it with water or ice.

    Here's the mass breakdown of this balloon, with the same tracker electronics as the previous launch:

    Item	Mass
    2 solar cells & carbon fiber stick	5 g
    Beacon PCB w/supercaps	7 g
    Upper wire	1.5 g
    Lower ...

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12. Picoballoon Launch 3

    On the morning of Saturday April 10, 2021, members of the San Francisco High Altitude Balloon group launched another picoballoon from the Berkeley Marina. Launch location was the south tip of Shorebird Park, and the launch party was Martin W6MRR, Robert K6RGG, Peter W6DEI, and myself.

    Balloon Hardware

    The hardware was very similar to the previous launch. The one big change this time was that the APRS 144.39 MHz transmitter was removed. This 500 mW transmitter took a lot of power, and sometimes RFI would lock the processor up bad enough that the balloon needed to power off completely before it would reset. The only transmitter on this balloon was WSPR on 14.0956 MHz.

    

    Output power of WSPR ...

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13. Telemetry from an Oakland Radiosonde Floater

    In the beginning of March, something happened to the regular cadence of radiosonde launches from Oakland Airport. No balloon was launched on March 11th 2300 UTC, nor the next standard launch window on March 12th 1100 UTC (5am Pacific time). The SDM Ops Status Messages had a 10142 error for Oakland, which is ground equipment failure. I'm guessing that something broke or got jammed on their autolauncher, or maybe they ran out of hydrogen gas.

    By the afternoon of March 12th, the issue appeared to be resolved, and there was three launches in quick succession. The first and third balloons, S3231708 and S2321334, were normal, but the middle balloon slowly rose and leveled out around 35,000 meters (~115,000 ...

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14. March 2021 Berkeley Picoballoon Launches

    As part of the San Francisco High Altitude Balloon group, Martin W6MRR has been experimenting with picoballoons. Picoballoons are different than regular amateur radio balloons in that are designed to be neutrally buoyant at around 40k feet. This requires payloads that are much lighter than traditional balloons, and different balloon materials that won't stretch or break. This altitude was picked because it is above airplanes and weather, but still in the jetstream, where they can float around the world in a matter of weeks. Our goal is to circumnavigate the globe at least once.

    Picoballoons use either Mylar or plastic material in their construction. More traditional Amateur radio balloons, like from our previous launch use latex, which expand dramatically at ...

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15. An Atmospheric River of Radiosondes

    I recently installed a new antenna (see below), and checking SondeHub a few hours later I noticed a bunch of balloons west of Sacramento. Well, that's pretty interesting. There aren't any regular launches near Sacramento, so this must be something special. They seemed to be launched frequently, because when I stopped receiving one balloon I immediately start receiving the next.

    

    These balloons were far away! I guess this new antenna works a lot better than the old one. Trying to back out the launch location, it seemed like they were being launched from Beale AFB, which is directly east of Yuba City. Maybe a military project? The military does launch a lot of radiosondes, but those are usually in Arizona ...

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16. Two Months of Radiosonde Balloon Reception

    It's been two months since my first radiosonde recovery. In this post, I perform some analysis of the receiving stations at my apartment in San Francisco and my vacation home/parents place in Los Gatos. I also include the python code needed to generate your own plots.

    San Francisco Station

    Immediately after I got home from my first recovery, I converted my regular amateur radio station at my apartment to receive radiosondes. The external antenna is a Diamond X-50NA, which is a great amateur radio 5/8 wave 2m/70cm dual-band antenna. Coax up to the roof is about 80 ft of LMR-400, which is calculated at around 1.5 dB loss at 145 MHz and 2.5 dB at ...

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17. Two Radiosonde Payload Recoveries, and RS-41SGP Teardown

    I've been watching SondeHub for the past two months to, every day since my first recovery, but the winds have not been cooperating! Lots of radiosondes went into the hills east of San Jose, out into the ocean, into the Santa Cruz mountains, all the way down to Gilroy, or splashed down in the bay, but none have landed in populated areas within an hours drive of my home in San Francisco. I realized how lucky I was that the first radiosonde I successfully tracked actually landed in a populated place.

    In a typical city, approximately 35-50% of the land is dedicated to cars: residential roads, arterials, freeways, and parking lots. So when a balloon lands in populated areas of ...

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18. Oakland Radiosonde Investigation, Launch, and Recovery

    I've recently stumbled upon the radiosonde_auto_rx project. I've always been interested in tracking radiosondes, and even watched a radiosonde launch in Inuvik, NWT a few years back. Worldwide, there are over 800 launches every twelve hours of every day, and this data feeds into weather forecast models.

    The radiosonde_auto_rx project is built around decoding many different types of radiosondes with a software-defined receiver. The preferred receiver is a RTL-SDR Blog v3, and I already had an extra one of those (because they are so inexpensive!).

    Most radiosondes worldwide use 400-406 MHz as their downlink, but the United States also uses some frequencies around 1680 MHz. Reading the documentation on which frequencies are in use, it appeared ...

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