1. Building a Quarter-Wave Ground Plane Antenna

    After my talk at Pacificon a few months ago, several people reached out to me about setting up a radiosonde receiving station at their house. They specifically had questions about the antenna and LNA, and after answering the same question a few times I decided to do a post about this topic.

    Building a 1/4 wave ground plane antenna is very easy to do. The overall design is simple, with a vertical element surrounded by a ground plane consisting of two or four wires bent down. Here are the dimensions for the VHF/UHF amateur radio bands (from the ARRL Handbook), but these dimensions can be scaled to any frequency.

    Quarter wave vertical antenna construction diagram

    There are many online calculators that will give you ...

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  2. Vandenberg Radiosonde Launches

    Just after setting up a remote receiving station in the hills above Santa Cruz for tracking radiosondes launched from Monterey Bay, I started noticing some weird stuff with the station. The station would detect a LMS6-403 radiosonde, but was unable to actually decode anything. The "jamming" signal was always on the same frequency of 400.259 MHz, and occurred daily around noon and midnight UTC.

    I speculated that it might be radiosondes from Vandenberg Space Force Base, approximately 300 km (~180 miles) south of the receiver along the coast of California. Although it would be cool to receive those radiosondes, the purpose of this station was to track the Monterey Bay radiosondes, so I put that frequency on the blacklist ...

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  3. Picoballoon Launch 19: Midway Islands

    The SF-HAB group launched another picoballoon on December 11th, 2021, from the Berkeley Marina. The launch party was Martin W6MRR, Robert K6RGG, and Kazu AG6NS. This picoballoon used two clear Chinese party balloons with hydrogen gas for lift. Martin's custom electronics was used, with a WSPR transmitter that alternated 14 MHz (20 meters) and 10 MHz (30 meters).

    The aprs.fi callsign was W6MRR-22 using the WSPR to APRS bridge, and the WSPR callsign was W6MRR.

    W6MRR-22 picoballoon trajectory

    This picoballoon floated between 9,900 and 11,100 meters (32.5k to 36.5k feet) for the duration of the flight, which is the perfect altitude for picoballoons. This is above most bad weather (rain and thunderstorms), but still low enough to be ...

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  4. Picoballoon Launch 18: Almost around the World!

    While the previous Lodi picoballoon was floating over Mexico City, we launched another picoballoon from the southeast corner of the Berkeley Marina on November 13th, 2021. The launch party was Martin W6MRR, Robert K6RGG, Kazu AG6NS, and myself KF6ZEO.

    W6MRR-21 picoballoon launch

    The forecast for the morning was no wind, and when we arrived at 10am the winds felt pretty calm. But after assembling the picoballoon train, it was apparent that even the very light breeze was too strong. The two clear Chinese party balloons were bent over, threatening to scrape against the ground.

    We waited almost 30 minutes for the winds to die down enough to release the picoballoon. During a bit of a lull in the wind, we walked across the ...

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  5. Picoballoon Launch 17: Lodi to Florida

    SF-HAB's Central Valley Division launched a picoballoon from Lodi, California, on Thursday November 11th, 2021. The launch party was David WB6TOU and Skip N6NFB. The tracker electronics used this time was a ZachTek WSPR Pico transmitter. Two Chinese party balloons were used for lift.

    ZachTek WSPR Pico transmitter front

    ZachTek WSPR Pico transmitter back

    The WSPR callsign for the balloon was N6NFB, and the APRS callsign was N6NFB-1.

    Launch party

    N6NFB-1 Flight Results

    Unfortunately, the tracker electronics did not power up on launch day, November 11th. We thought all was lost, but it awoke the next day in Maidenhead grid square DL58, which is ~1640 km (~885 mi) southeast of the launch location. The balloon was at an altitude between 9,900 and 11,100 meters (~32.4k to ~36.4k feet ...

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  6. Newfoundland Radiosonde Launches

    I recently went on a work trip to Newfoundland, Canada. Checking Sondehub before I left, I saw that there were two radiosonde launching stations on the Island of Newfoundland, one on the west side in Stephenville, and the other on the far east end in St. John's. And as luck would have it, I was traveling to Lewisporte, which is on the Trans-Canada highway almost halfway between the two launching sites. I might be able to receive both sondes at the same time!

    As far as I could tell, the radiosondes launched at both of these sites were Graw DFM-09P (pdf), which transmit around 403 MHz. One interesting thing about these radiosondes is that they don't transmit a serial number ...

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  7. Pacificon 2021 Picoballoon and Radiosonde Presentation

    David WB6TOU, Martin W6MRR, and myself gave a presentation at the Pacificon, which is the annual ARRL Pacific Division ham radio conference held in San Ramon in the fall. Our presentation was titled "Picoballooning in the Bay Area: High Altitude Balloons, Picoballoons, and Radiosondes." Download the slides here.

    We also used this opportunity to launch the new SF-HAB website, which is a collection of how-tos, resources, and blog posts about our ballooning activities.

    The first third of the presentation was David talking about balloon mechanics, including how to prestrech, fill, measure, and release SBS-13 and cheap Aliexpress picoballoons. David launched two SBS-13 picoballoons from the Central Valley in winter 2021, one of which went 2.5 times around the world ...

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  8. October 2021 Picoballoon Activities: Launches 12 thru 16

    In the beginning of October 2021, we had a flurry of launches from the Berkeley Marina. In the span of two weeks, we launched five balloons. All of the picoballoons woke up after launch, which means that we are getting better at building, testing, and launching picoballoons. But unfortunately, only one of them survived the first night and woke up the next day. We can't achieve our goal of going around the world if the picoballoons only last for one day!

    All of these picoballoons used the same custom electronics designed and built by Martin W6MRR. Two cheap Aliexpress 36-inch clear plastic balloons were used, with around 6 grams of free lift.

    Picoballoon Launch 12: K6RGG-11

    On Thursday, Sept 30th ...

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  9. Picoballoon Launch 11: The Intermittent Picoballoon

    We launched again on Monday, September 20th, 2021, from our usual spot in the Berkeley Marina. The launch party was Martin W6MRR and Robert K6RGG, and the launch time was a bit later than usual at 11:30am Pacific time (1830 UTC). The picoballoon did not wake up on launch day. After our previous halfway around the world picoballoon, we were a bit dismayed to have another failed launch.

    WSPR.rocks map overview

    But the following day it woke up! The picoballoon was meandering out in the Pacific Ocean in gridsquare CL79, somewhere between 9,900 and 11,100 meters (32.5k to 36.5k feet). While this is higher than most of our previous picoballoons, our ideal altitude is above 11,100 meters ...

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  10. Picoballoon Launch 10: Halfway Around the World!

    At the beginning of Week 3 of Launch 10, we were getting excited that this balloon might circumnavigate the globe. The prediction made from the middle of Egypt showed strong winds would take the balloon to the West Coast within 5 days, maybe even crossing the -122 degree longitude line of our launch site before heading back out to sea.

    HYSPLIT trajectory forecast

    Flight Results

    Unfortunately, the picoballoon only survived two more days in the Middle East. In a situation eerily similar to W6MRR-17, a single packet was received from the ground in southwest Uzbekistan near the Turkmenistan border. The altitude reported was less than 900 meters (encoded in the WSPR power field as 0 dBm or 1 mW). Maybe the tracker was ...

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