Linear Translators on Balloons

Presented by Carl Lyster, WA4ADG, at Hamvention 2025.

The presenter shares details of an innovative 1990 balloon flight carrying a homemade linear translator, dubbed the "poor man's CubeSat." Built from scavenged parts for just $50, the translator relayed HF signals up and VHF down, enabling contacts as far apart as 593 miles. Using a 100 milliwatt transmitter and operating at around 100,000 feet, the balloon facilitated reliable QSOs between stations in Marietta, Ohio and Marietta, Georgia. The system received on 28.44 MHz and transmitted on 144.3 MHz, supporting simultaneous contacts thanks to a 22 kHz bandwidth. The flight also featured a low-power beacon and, though the payload wasn’t recovered, it demonstrated the surprising effectiveness of low-cost amateur-built space hardware.

The presenter contrasts linear translators with traditional FM repeaters, explaining how the translator's simplicity and flexibility allow multiple modes—CW, SSB, AM, and more—without converting signals to audio. Though more power-hungry due to Class A operation, linear translators are simpler electronically and better suited for emergency communication. The talk includes photos of the original flight hardware, hand-drawn circuit boards, and even a humorous tech repair story. A short audio clip of the historic flight captures real-time QSO audio. Carl also demos a newer translator design and discusses the potential for future field day launches or emergency deployments using similar balloon-borne platforms.