AN EXPLORATORY TEST OF DATA TRANSFER BY VHF TO AIRCRAFT OVER THE OCEAN IN A TROPOSPHERIC PROPAGATION ENVIRONMENT.
NATIONAL AVIATION FACILITIES EXPERIMENTAL CENTER ATLANTIC CITY N J
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Two very high frequency VHF troposcatter antennas, each with 16 colinear dipoles in a vertical array, were installed about 80 wavelengths apart at a site near the coast at Avalon, New Jersey. These antennas had flat, broad, high-gain radiation patterns directed in parallel toward the horizon. Exploratory tests were conducted while transmitting test signals, in a controlled sequence, between the site and a project aircraft operating over the ocean. In the sequence of test signals, a period of no modulation was followed by a calibrated audio tone, teletype messages and voice messages. Each sequence was repeated so that performance during phase modulation of the VHF transmitter could be compared with performance during amplitude modulation. The test site, test experience, and data are described as guidance for further experimentation in the same environment. The test indicated that simple substitution of low-speed data modulation for voice modulation, or of phase modulation for amplitude modulation, would not produce a substantial change of performance in a system designed for voice communications. The report recommends a test to determine probable operational coverage of these troposcatter antennas. Author
- Air Navigation and Guidance
- Radio Communications