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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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 transmitting. The transmitter output power is a fixed 10 mW, and the altitude of the balloon is encoded in the "power" field of the WSPR packet according to this chart:

The WSPR callsign of this balloon was again W6MRR, and using the aprsWsprBridge.py script, was piped into the APRS network using the callsign W6MRR-16.

Launch

The big change we ...

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I recently read an article about how a "cold blob" was interrupting the Atlantic Meridional Overturning Circulation (AMOC). This is pretty interesting, as the AMOC takes heat from Florida and brings it to Europe, keeping Europe warmer during the winter. The fear is if this current stops, winters in Europe will become a lot colder than they currently are. Towards the end of the article, they talk about using ocean float data for in situ measurements. That jogged my memory, I actually helped to deploy these ocean floats a long time ago!

In spring 2005, during my junior year at Cal Poly San Luis Obispo, I participated in the Cal Poly At Sea program. This partnership between Cal Poly and Cal Maritime invites Cal Poly students to take classes about the Training Ship Golden Bear for two months. The trip was great, we sailed from San Francisco to Hawaii, Suva, Noumea, Sydney, and Brisbane, with a stop off at Palmyra Atoll on the way back to Hawaii. Professors from Cal Poly taught real classes on environmental chemistry, biology, astronomy, and ...

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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 wire	0.9 g
Total payload	15.24 g

The two balloons weighed 71 grams, and after filling with hydrogen had a net neck lift of 23 grams, for a total free lift of 8 grams. This lift should give the balloon a final altitude of 11,500 meters (~38,000 ft), which is above any weather.

Since longevity of ...

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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 transmitter is only 10 mW. Since the WSPR protocol only includes a Maidenhead gridsquare and not altitude, we encoded the altitude using the Power field in the WSPR protocol. This is described more by ZachTek (PDF). This chart shows the different Power values corresponding to the altitude bands.

Software

The ground software to post the WSPR packet on the APRS ...

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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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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 altitude, then bursts. Latex balloons also break down under ultraviolet light, and are much more expensive than plastic balloons.

Early picoballoon launches just used 2m APRS for sending position information. However, the APRS frequencies in Europe and the rest of the world are different than the North American standard of 144.390 MHz, so balloons that crossed the Atlantic needed ...

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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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Update July 2021: Run rtl-ais and kplex in a docker container.

At the conclusion of my last AIS blog post, I noted that the AIS receiving station I had set up was not sustainable for the long term. It was using a full hardware radio, and the software was running in a Windows 7 virtual machine on my personal laptop. Since AIS decoding is not super useful only when my laptop is powered on, a new station setup was needed.

One option would be buying a dedicated Raspberry Pi with a dAISy Hat receiver. It's a dual-channel receiver that spits out UART serial NMEA frames to the Raspberry Pi, and costs $70, plus a Pi for $35. But that's a lot of money for something that I don't really get any benefit from.

One Pandemic Positive is that I have a lot of free time on my hands, so I thought about receiving AIS signals using equipment I already own. I have an extra RTL-SDR Blog v3 receiver, and after searching the internets I found the rtl-ais project, which seemed ...

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I recently moved, and while packing up boxes I found my FunCube Pro+ receiver dongle. One of the many Pandemic Positives is that I have a lot of free time on my hands now, so I thought I would see if I could receive amateur satellites with this. Perusing the AMSAT live Oscar satellite status page, the only recently-launched CubeSat I could receive with the FunCube Pro+ dongle is AO-95, also known as Fox-1Cliff. And even then, the satellite appeared to be in Safe mode, with its transponder not working due to a failed receiver.

Fox-1Cliff is named for Cliff Buttschardt K7RR, who was the amateur radio mentor for the PolySat project at Cal Poly. He was also heavily involved with AMSAT, ARRL, and Project Oscar, which is another amateur satellite organization that launched the first OSCAR satellites back in the early 1960s. He passed away in July 2006.

I was an undergrad at Cal Poly from 2002-2008, and he was a constant presence in the lab. Cliff, along with Ed English W6WYQ (SK), mentored the Cal Poly students in ...

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