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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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 450 MHz, plus connectors. Because this had a base station radio attached, it didn't have an LNA or filter up at the antenna.

Here is a pic of the antenna, mounted to a 5 ft pole that is clamped to a steel sewage roof vent. This is a very easy (temporary) installation. The Nanostation M5 also installed is part of ...

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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 the Bay Area, there's a really good chance that it's going to land on or near some car infrastructure. Even my neighborhood in San Francisco, one of the densest cities in America, dedicates 28% of surface area to cars: from the center stripe to the front of the house is 40 ft, and the lot is 100 ft deep. Cars ...

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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 that 1680 MHz was being used at Oakland, but they were transitioning over to 400 MHz "sometime in 2020." So first step was to install the software, then find what frequency band the radiosondes were on.

Software Install

The radiosonde_auto_rx program is designed for Raspbian/Debian systems. I use a crappy laptop with Ubuntu for my APRS balloon tracking, so I decided to use ...

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