Demonstration of Bandwidth Capabilities of Beyond-Horizon Tropospheric Radio Propagation

Tropospheric radio transmission beyond the horizon is characterized by rapid and selective fading, which suggests a possible limitation on the useful bandwidth. The tests discussed were made to explore the bandwidth capabilities of this medium. Bell Telephone Laboratories conducted these tests in cooperation with the M.I.T. Lincoln Laboratory on a 188-mile path at 5,050 mc with a power of 300w and 28-foot paraboloidal antennas. Two types of tests were made. First a 12-voice-channel multiplex system for intermodulation crosstalk. IF band was 1.3 mc. Then television tests were made with a deviation of ±4 mc and IF bandwidth of 30 mc. No significant impairment in system quality could be attributed to distortion in transmission medium in either test.