Aircraft Loran-C Dual-Loop Antenna System Design and Flight Test

Dick H. van Graas and Frank van Graas

Abstract:	Precipitation static (P-Static) can cause severe degradation of the received Loran-C signal quality onboard an aircraft in flight if a wire antenna is used. Aircraft flight through snow, for example, can result in degraded signal-to-noise ratios (SNR) and loss-of-lock, resulting in the loss of the Loran-C navigation function. To mitigate the effects of P-Static, a dual-loop antenna system for airborne Loran-C signal reception was designed, implemented and flight-tested. The antenna system consists of a cross-loop antenna and an ultra low-noise pre-amplifier. The pre-amplifier is connected to an aviation Loran-C receiver approved for instrument flight rule (IFR) conditions. An Automatic Direction Finding (ADF) antenna was used, without modification, for the reception of the Loran-C signals. This antenna satisfies Technical Standard Order (TSO) C41b for aircraft ADF antennas. The pre-amplifier was designed to optimize the reception of the Loran-C signals and to combine the signals from the two antenna loops. For accurate navigation purposes, phase corrections are required in the Loran-C receiver to compensate for the antenna phase pattern. Both wire and loop antenna systems were tested on a single-engine Beechcraft Bonanza aircraft during normal and P-Static flight conditions. Flight test results show that the Loran-C receiver connected to the wire antenna experienced degraded SNRs during snow-induced P-Static, while the Loran-C receiver connected to the dual- loop antenna was not affected by the P-Static.
Published in:	Proceedings of the 2001 National Technical Meeting of The Institute of Navigation January 22 - 24, 2001 Westin Long Beach Hotel Long Beach, CA
Pages:	369 - 376
Cite this article:	van Graas, Dick H., van Graas, Frank, "Aircraft Loran-C Dual-Loop Antenna System Design and Flight Test," Proceedings of the 2001 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 2001, pp. 369-376.
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