Back in October 2021, the excellent team behind Sondehub added several features to the map. They added launch site locations, grabbed from the official NOAA database. Clicking on a particular launch site allowed a user to generate a weeks worth of flight predictions based on the most recent GFS run. Cool!

The red lines on this prediction map of Oakland show the next 14 launches (7 days). As with any prediction of the future, the further out you go the worse the prediction.

Reverse predictions (pdf) were also added, for predicting where a radiosonde was launched from. This feature would have been very helpful when I was trying to find the Monterey Bay launch location.

Scrolling around the new map, I saw a launch site just east of Houston, Texas. I knew some people that lived in Houston, so I sent them a radiosonde receiving station. The hardware was almost identical to the Santa Cruz station, except that this station is entirely inside a home. No weatherproof case was needed, which is great because I didn't really want to figure ...

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Now that the pandemic has tapered off a bit, I took another short trip up to Inuvik, NWT. While I was up there, I visited the Environment Canada Weather Station, and participated in a radiosonde launch.

The big news out of Inuvik during this trip was that the road from the airport to the town has been paved! The road is much smoother, and I don't need to worry about windshield cracks every time a big truck passes.

Since my 2016 visit, the site has been upgraded with modern equipment. The old Electrolyser Corporation hydrogen generator was replaced with a Proton Hogen unit, all housed in a modern building with explosion-proof light switches, electrical outlets, etc.

I arrived just before the Midnight UTC launch, and Chris already had the balloon inflated and was working on the radiosonde transmitter. As I saw in Newfoundland, Canada has transitioned to the Graw DFM-09 radiosonde.

To my surprise, he actually let me release this radiosonde. This was my first radiosonde release, and it's very similar to a bursting HAB release. One interesting aspect of ...

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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.

There are many online calculators that will give you the approximate dimensions for the elements, but I usually use M0KUD's calculator. Whenever you are making antennas, always cut your elements a bit longer (maybe 20%) than the calculation says, then trim them during tuning.

Use any type of wire for the elements. I use standard 14-gauge solid copper wire because it's easy to get from the hardware store, it's ...

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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 and turned my attention to the task at hand.

New LMS6-403 Radiosonde Version

A few days later, my curiosity got the better of me, and I started to investigate these signals. Over the course of four days, I did decode a single packet each from two radiosondes. Based on the location, these definitely were from Vandenberg, but the signal must ...

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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 with every packet, so it takes a while to determine the serial number of the radiosonde you are receiving.

Receive Station

Since I was traveling, I needed a portable station with two receivers. This is very similar to my standard radiosonde receive station at home, and I didn't use a preamp or filter.

The Comet M-24M dual-band amateur radio antenna ...

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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.

The second third was Martin talking about picoballoon electronics. He discussed using APRS and WSPR for publishing telemetryon the internet. Martin designed and built a custom tracker for all of the picoballoon launches we have done from the Berkeley Marina.

The last third of the presentation was yours truly talking about radiosondes. I gave a brief overview of their purpose ...

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Taking a look at SondeHub one evening in early July 2021, I noticed some radiosondes down in the Monterey Bay, about 75 miles south of San Francisco. There seemed to be one per day in the afternoon on most days. The Naval Postgraduate School launches radiosondes very infrequently for their meteorology program, but these seemed to be launched from Watsonville or Salinas, not the main NPS campus in downtown Monterey.

Then, on Monday July 12th, there was a flurry of radiosondes launched. I received a total of 5 of them from my station in Los Gatos. This station does not have good coverage in the direction of Monterey, and only starts receiving radiosondes when they rise up to 5,000 meters (~16k feet), above nearby mountains.

This rate of around 5 launches per day was sustained until Friday July 23rd. I was pretty busy with other things in life during this period, so I didn't really pay attention to these launches or landings.

Then on August 20th, many radiosondes started appearing in the sky again, and this time I was ...

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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 2020, when I started receiving them. Each red dot is the last position received by my two receiving stations, and is typically less than 1,000 meters altitude. This map shows 337 radiosondes, and I have removed the radiosondes launched up north by UCSD during atmospheric river events. As you can see, they are mostly south and east of the ...

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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 feet), and became a "floater" radiosonde. Maybe was underfilled with hydrogen gas, or had a hydrogen/air mixture instead of pure hydrogen.

The serial number of this floater balloon was S3240385, and it launched around 20:40 UTC on March 12th.

Due to buildings in the way, I stopped receiving the balloon west of Santa Cruz, and started picking it ...

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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 in support of Aerostats patrolling the border.

The program I use to decode radiosondes, radiosonde_auto_rx, supports multiple receivers, so I stole a RTL-SDR from my AIS station and continued receiving. The next day I saw radiosondes above Santa Rosa as well.

Where were all these coming from? Using the telemetry I was directly receiving from the balloons, and the low-level ...

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