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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In September 2016 I visited the Environment Canada Weather Station in Inuvik, NWT. I arrived just as they were preparing for the 2300z weather balloon launch, and they let me hang around and take some pictures.

Every twelve hours around the globe, approximatley 800 radiosondes are launched. These weather balloons record temperature, pressure, humidity, and location from the surface all the way up to 100k feet, or higher. These measurement are fed into weather models for long-term weather forecasting. These launches happen worldwide at 1100 and 2300 UTC, which gives the balloon enough time to be up at altitude around noon and midnight UTC.

This is the Vaisala RS92-SGPD radiosonde, which measures location, pressure, temperature, and humidity as the balloon ascends. The helix antenna in the upper right is for GPS, and the silver strip below that has two temp sensors and a humidity sensor. The 402.7 MHz wire antenna is on the bottom of the unit, on the left side. The 200 ft of string on the spool attaches to the balloon.

The balloon is filled with locally-generated ...

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