Tagged: HAB

Tracking Multiple Amateur Radio APRS Balloons with RTL-SDRs

Last month Jeff Deaton from "Edge of Space Sciences" (EOSS) presented a talk called "SDR Multi Balloon Tracking", where he discusses how EOSS are using RTL-SDR receivers to track their APRS high altitude balloons. EOSS is a Denver, Colorado based non-profit organization that promotes science and education by exploring frontiers in amateur radio and high altitude balloons. The talk overview reads:

Review of the software defined APRS system being used to track multiple balloon flights at EOSS. Overview of primary features like the graphical user interface and landing predictions as well as a discussion of the open source software used to power the system like GnuRadio, Dire Wolf, and Aprsc.

It appears that they've created some interesting software that they run on small portable computers that they take in chase vehicles. The software uses an RTL-SDR to receive the APRS signal from the high altitude balloons that they've launched, allowing them to track and predict the flight path, and ultimately recover the balloons and attached cameras.

SDR Multi Balloon Tracking

Creating a High Altitude Balloon Telemetry System with Raspberry Pi, RPiTX and RTL-SDR

The 2M TX Filter by ZR6AIC
The 2M TX Filter by ZR6AIC

Over on his blog ZR6AIC explains how he's created a full HAB (high altitude balloon) telemetry transmit and receive system using RPiTX and an RTL-SDR dongle running on a Raspberry Pi 3.

RPiTX is software that enables the Raspberry Pi to transmit any modulated signal over a wide range of frequencies using just a single GPIO pin. However, the transmission contains multiple harmonics and thus requires sufficient filtering in order to transmit legally within the 2M ham band. To solve this ZR6AIC uses a 2M Raspberry Pi Hat kit which he designed and created that contains two low pass filters as well at the option for an additional power amplifier.

The rest of ZR5AIC's post explains how his HAB telemetry system combines the Raspberry Pi 3, RPiTX 2M Hat, RTL-SDR, a GPS unit, battery, temperature sensor and optional camera into a full HAB transmitting system. He also explains the software and terminal commands that he uses which allows him to transmit via RPiTX a CW beacon and GPS and temperature sensor APRS telemetry data with the Direwolf software. Full instructions on setting up the alsa-loopback audio routing is also provided.

Launching the High Altitude Balloon.
Launching the High Altitude Balloon.

Creating a FSK SSDV data system for High Altitude Balloons

David and Mark are building a 115 kbit/s FSK SSDV (slow scan digital video) data system for high altitude balloons. In their system, on the balloon transmit side they use a Raspberry Pi, Raspberry Pi camera and a RFM22B wireless transceiver modulator board to transmit the SSDV FSK signal. On the receive side they use an RTL-SDR dongle, low noise preamplifier and a GNU Radio program to demodulate the SSDV images. The first video below demonstrates the hardware and GNU Radio program and shows them receiving the SSDV signal. In the second video they demonstrate that the images can be received at low signal levels (-106dBm) as well, by heavily attenuating the signal.

115.2kbaud FSK Modem Test
115.387kbaud FSK Modem Test – Part 2

If you are interested, all their code for the SSDV system has been uploaded to https://github.com/projecthorus/HorusHighSpeed.

While testing the RTL-SDR for use in this system they also measured the noise figure of an R820T RTL-SDR dongle. The noise figure at maximum gain comes out at around 5.6 dB. By adding a low noise amplifier they reduce the measured noise figure down to 2 dB.

Testing the attenuated SSDV signal reception with an RTL-SDR.
Testing the attenuated SSDV signal reception with an RTL-SDR.

HackRF Decoding PICO High Altitude Balloons (HAB)

Blogger g0hww shows us how he used his HackRF to decode Pico high altitude balloon (HAB) transmissions using gqrx and dl-fldigi. Pico balloons are small party sized high altitude balloons, typically launched by hobbyists. They have enough lift to carry a small sized ~60g payload. Since they are so small, they are usually exempt from requiring permission from the authorities, unlike full sized weather balloons.

The cheaper RTL-SDR could also be used to track these balloons.

PICO High Altitude Ballo0n Recevied with HackRF

RTL-SDR Tutorial: Receiving Weather Balloon (Radiosonde) Data with RTL-SDR

Around the world meteorological weather balloons are launched twice daily, and continuously transit weather telemetry to a ground station using something called a radiosonde. The RTL-SDR software defined radio combined with a decoding program can be used to intercept this telemetry, and display it on your own computer. You will be able to see real time graphs and data of air temperature, humidity, pressure as well as the location and height of the balloon as it makes it's ascent.

Note that if you are in the USA, then this tutorial may not be applicable for you as different radiosondes are used. Instead have a look at this post which shows how to use the SkySonde software from NOAA. You can also try an alternative command line based decoder called RS available on GitHub.

This tutorial is also applicable to other software defined radios such as the Funcube dongle, Airspy, HackRF, BladeRF or even hardware radios with discriminator taps, but the RTL-SDR is the cheapest option that will work.


In this example YouTube user Superphish shows a radiosonde being received and decoded using a RTL-SDR, SDRSharp and SondeMonitor.

Weather Balloon (Radiosonde) tracking with RTL SDR (RTL2832), Sondemonitor and SDR Sharp

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