Design of a Low-Cost Data Communications/R.F. System for use with Low Earth Orbiting Store and Forward Satellites

The functional requirements and system overview for a low cost data communications system for small satellite use are presented. Tradeoffs of system parameters will be discussed such as: cost, transmission speed, power consumption, spectrum useage, and system complexity. Link calculations at 137 MHz, with transmission speeds of 9600 BPS, monopole antennas, and a 50kHz bandwidth show that adequate signal margins can be obtained with 2 Watts of R.F. power for most conditions. Use of low cost, amateur or commercial type radio equipment requires only minor modifications, and creates small reliability and performance risks.