Small Stratospheric Payload for Over-the-Horizon Communications, 16-R9689

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Principal Investigators
Phillip Beverly
Kurt A. Franke

Inclusive Dates:  02/14/07 – 06/27/07

Background - This project began with a proof-of-concept repeater, consisting of an HT1000 radio with battery pack, MFJ-662 repeater, and custom cable. The MFJ-662 repeater is a simplex repeater with 30-second audio buffer. It is meant to be connected to any single-channel radio or handheld radio transceiver to provide communications over an extended range without the cost and complexity of a duplex repeater. This project addresses the environmental hardening and reconfiguration of the equipment for over-the-horizon (OTH) relay of voice and data packets. The complete payload will be compact and thermally hardened for future use with the SkyWisp™ balloon-borne stratospheric glider system.

Approach - The technical approach began with making baseline measurements of the operating temperatures of the commercial off-the-shelf (COTS) components. Limiting components ("weak links") were found and remedied with replacement or localized heating and insulation. This included a re-layout of the simplex repeater circuit board to use industrial temperature range components and for compactness. The target goal was a small compact payload that operates from -40 degrees C to +50 degrees C ambient temperature (i.e., without packaging or insulation, except on a small set of individual components). This is the same operating temperature range required for the glider avionics. A prototype battery pack was also constructed with heater and insulation. Battery power must be used for heating components as well as running the repeater payload. The battery performance goal (suitable for a demonstration) was two hours of operation at 40 degrees C ambient temperatures.

Accomplishments - This project produced a thermally hardened and laboratory tested demonstration payload. The payload meets the operating temperature goals, and is small and self-contained for future glider tests. Potential customers that have seen the payload operate have been impressed with the size, voice quality, and overall capability. Operating time using the prototype battery pack is expected to be at least two hours under anticipated temperature and operational conditions.

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