VHF Transhorizon Communication System Design

The basic properties of a signal received over a typical VHF transhorizon circuit are presented. The necessary parameters and features of a system designed to utilize efficiently this signal are then considered. These include modulation, diversity reception, teletype transmission, frequency control, equipment reliability, and duplex operation. In conclusion curves are presented showing system voice and data channel capacity and quality as a function of circuit length, reliability required, and frequency. It is concluded that available VHF equipment may be employed to provide reliable voice transmission and extremely reliable multichannel teletype transmission for circuits in the 300 to 1200 mile range.