Older articles:

1. Sondehub Grafana Graphs for December 2024 High-Altitude Balloon Launch

   In December 2024, the SF-HAB group flew a high-altitude balloon from the San Francisco Bay Area. The flight was a partial success, with the payload recovered the next day. Only several weeks later did I find out about this excellent Sondehub Grafana instance, hosted on AWS and directly connected to the Sondehub Amateur database.

   In this post, I want to dive a bit deeper into the Horus Binary v2 telemetry that was transmitted from a reprogrammed RS41 radiosonde on this flight. This entire post is commentary and screenshots from this grafana dashboard, screenshotted here to reduce link rot. All times are in UTC on Dec 15th 2024.

   Balloon Position Graphs

   Due to the under-inflated balloon, we knew it was going to rise slower than predicted, and burst at a higher altitude. This balloon reached a maximum of 37,412 meters (~122.7k feet) at 21:09:57.

   

   This is a graph of the ascent and descent rates for the whole flight. The blue line is what the GPS reports (in meters/sec, left axis), and the yellow line is calculated ...

   Read More →

2. December 2024 High-Altitude Balloon Launch

   On Sunday 15 December 2024 the SF-HAB group got together and flew a bursting high-altitude balloon. We had a whole crew there, including Martin W6MRR, Kazu AG6NS, Robert K6RGG, John NI6D, Walter K6ATV, Benjamin KO6CNT, and Steve K6WW. Everyone helped out with assembling the payload train, filling the balloon, or documenting the launch.

   Preflight Planning

   The days before the flight we had an atmospheric river in the Pacific Northwest, so the upper winds were very unsettled. The lower-level winds were also blowing all different directions, and it rained significantly the day before. But the weather forecast for launch day was clear and sunny, and the Sondehub predictions showed a general Southeast flight. We picked Walnut Creek as the launch location to have our balloon land on the eastern side of the Central Valley

   

   Balloon Assembly and Filling

   The launch site was at a local park in Walnut Creek, and we met at 9:30am on a very cool and cloudy day. There was no wind at all. The balloon was a standard Kaymont 1500 gram filled with hydrogen.

   

   Unfortunately, during ...

   Read More →

3. Reprogramming a RS41 Radiosonde for Amateur Radio Frequencies

   I decided to re-fly a Vaisala RS41 radiosonde on an upcoming SF-HAB high-altitude balloon launch. The radiosonde must be reprogrammed on amateur radio frequencies, and I decided to use the RS41ng project by Mikael Nousiainen OH3BHX. This post is a companion post to setting up a Horus Binary receiving station.

   Radiosonde Hardware

   The radiosonde I randomly pulled out of my box was V1920305, launched over a year ago from Oakland on 8 August 2023. I picked it up the next morning from a construction zone in South San Francisco, and the construction guys just gave it to me after I asked about a balloon.

   

   Building the firmware

   On Linux, building the RS41ng firmware is ridiculously easy. You build a local docker container with the build environment, which takes up about 2.2 GBytes of storage (!?). After editing the configuration file, one command builds the firmware inside the docker container.

   Here are the commands I ran, stolen from the detailed linux docker procedures:

   ~$ git clone https://github.com/mikaelnousiainen/RS41ng
   ~$ cd RS41ng
   ~/RS41ng$ vim src/config.h                                                        (edit with your configuration ...

   Read More →

4. Setting Up a Linux Horus Binary Receiving Station

   The SF-HAB group is talking about doing a High-Altitude Balloon launch in the next few weeks, and asked if I had any payloads to fly. I thought it would be fun to refly all these radiosondes that I have collected.

   Looking around a projects online for reprogramming radiosondes, I came across the the great work that Mark Jessop VK5QI was doing down in Australia. Mark and David Rowe created the Horus Binary protocol, which is a low-power 100 baud 4FSK modulation scheme specifically designed for high-altitude balloons. Mikael Nousiainen OH3BHX wrote the RS41ng project which implements the Horus Binary transmitter on a regular Vaisala RS41 radiosonde.

   The next blog post will focus on reprogramming the RS41 radiosonde.

   Hardware Setup

   The hardware receiving the Horus is pretty much the same as receiving a radiosonde or AIS, except it's a different frequency so a different antenna must be used. While I list a Raspberry Pi 4 on the block diagram (running Debian 12 Bookworm), any Debian-based distribution can be used.

   

   The Mt. Carmel High School Amateur Radio Club (W6SUN) down in San ...

   Read More →

5. Keflavik, Iceland Radiosonde Receiver

   I spent a few weeks in Iceland in May 2024, working near the main airport in Keflavik. The area was a US Air Force/NATO base from 1951 until 2006, when it was turned over to the Icelandic government. The US Air Force returned in 2016.

   While I was there, I installed a radiosonde_auto_rx station. Iceland has one radiosonde launching site located at the Keflavik airport, and launches two radiosondes a day at 1100 and 2300 UTC. Skew-T plots are published by the Iceland Met Office after every launch.

   Hardware

   The hardware for this receiving site is the standard radiosonde receiving hardware. A Rasbperry Pi 3B+ and a RTL-SDR Blog v3 are the main components, along with an external antenna. All of the hardware sits on a rack shelf in the building.

   

   

   Antenna

   The air in Iceland is very corrosive from the volcanoes and salt spray. Any metal that isn't stainless rusts almost immediately, and even lower-grade stainless rusts after a few years. Since the receive antenna would be placed outdoors, my homemade quarter-wave ground plane antenna would be a ...

   Read More →

6. Japan Radiosonde Recovery and Tracking

   In July 2023 another work trip took me to Hokkaido, Japan. I stayed in Obihiro, a city of about 165,000 people. I brought along a RTL-SDR dongle and mag-mount antenna, and if I had some free time, I would try and decode nearby radiosondes.

   From my earlier trip back in September 2022, I knew there was radiosondes launched from Sapporo twice a day. However, it was unclear if the Kushiro autolauncher had been replaced after the fire.

   

   After tracking the radiosondes in Hokkaido, I would travel to Tokyo for a few days and try and track them in the city, labeled "Tateno" in the above map.

   Tracking Hardware

   The equipment I use is very simple but effective, just a RTL-SDR Blog v3, a mag-mount antenna, laptop, and car power supply.

   

   Pro tips for using this mobile setup:

   • Have someone else drive the car, or pull over whenever viewing the laptop.
   • Use a short USB extension cable instead of plugging the RTL-SDR dongle directly into your laptop. This prevents torque on the laptop's USB port.
   • Use a car DC-DC converter ...

   Read More →

7. Fairbanks Radiosonde Receiving Station

   After my visit to Fairbanks, Alaska back in July 2022, I chatted with a friend who lives in Fairbanks. He agreed to host a radiosonde receiver at his house just north of town. Since I wasn't traveling to Fairbanks again in 2022, I shipped him all the parts necessary for the installation.

   

   This station is the standard Raspberry Pi and RTL-SDR Blog v3 that I have been shipping around to Houston and other sites. radiosonde_auto_rx runs inside a docker container, which makes it trivial to install and update the software. For remote monitoring and control, wireguard is the way to go.

   Antenna

   My go-to antenna for radiosonde receiving is a quarter-wave ground plane antenna. They are super easy to build, very inexpensive, and work better than commercially-made antennas.

   But a home-made quarter-wave vertical antenna has one major flaw: ice. Ice buildup on the elements will not only cause it to detune, but there is also a potential for mechanical failure. Hardware store 14-gauge copper wire just isn't strong enough to hold up ice.

   Since Fairbanks gets a lot of snow ...

   Read More →

8. Kushiro, Japan, Radiosonde Autolauncher

   A recent work trip brought me to Hokkaido, Japan. Taking a look at Sondehub beforehand, I noticed a few radiosonde launch sites on the island. My work would bring me closest to the Kushiro radiosonde launch site, so maybe if I had some free time I could go watch a launch.

   Research

   Before leaving for the trip, I contacted Shaun JH1HNB/KJ6VGQ, who was uploading radiosonde data to Sondehub. Shaun lives in Tokyo, and has written some blog posts about his experiences.

   Shaun gave a presentation (pdf) in February 2022 to the Tokyo International Amateur Radio Association. The presentation was about using radiosonde_auto_rx or a rdzTTGOsonde to receive radiosondes.

   

   I also did some research on the Japan Meteorological Association's radiosonde webpage (pdf), which has a lot of information about the program. Their online map showed that this site uses an autolauncher, but doesn't indicate which type of radiosonde is launched.

   

   Since radiosonde_auto_rx can receive all three of the types of radiosondes that are launched in Japan, I felt confident that I could receive any radiosonde that was taking measurements.

   Kushiro ...

   Read More →

9. Fairbanks Radiosonde Autolauncher

   On the last day of my recent trip to Fairbanks, Alaska, I finished up work a bit early and headed to the airport to see a radiosonde launch. Looking at satellite imagery before my trip, the launch location has a few buildings so I thought it might be a manually-launched site like Inuvik or Newfoundland.

   However, when I arrived, through the fence I saw a Vaisala AS41 autolauncher, just like my local radiosonde launch site across the bay in Oakland, California. No one to talk with this trip.

   

   I arrived just before 3pm local time (2300 UTC), and the autolauncher was beeping away, indicating that the balloon was filling with hydrogen. I set up my mobile radiosonde_auto_rx station, with a mag-mount antenna and RTL-SDR dongle. Running the software inside a docker container makes it easy to install and update.

   

   The radiosonde was turned on and transmitting on 405.3 MHz inside the autolauncher, but the expected launch at 2300 UTC came and went with nothing happening. Interesting, maybe something was wrong? My local Oakland station launches at exactly 1100 and ...

   Read More →