Field testing of a VHF data link for air-ground data communications

The U. S. Department of Transportation has conducted a test program to determine the performance achievable by the mininum shift key (MSK) modem technique in air-ground data links. The method by which MSK may be used in the VHF air-ground data link system is described. The impact of performance limitations of existing equipment is described and experimental results obtained during ground tests and two flight test series are reported. It is shown that intersymbol interference and multipath are the predominant effects which must be characterized and modeled to obtain an accurate estimate of performance. The effort reported in this paper was sponsored by the FAA Systems Research and Development Service.