Design and Assembly of an Antenna Demonstration System

This paper describes the design, assembly, and operation of a self-contained wireless demonstration system that required only dc power supplies. The system demonstrated polarization effects, radiation patterns, gain, directivity, and signal interference from environmental barriers from dipole, corner reflector (simulated antenna array), Quagi, and embedded patch antennas. The system included an RF oscillator, high-frequency amplifiers,RF bandpass filters, a signal-strength indicator, and multiple adjustable antenna-mounting platforms

Summer and Winter Defoliation Impacts on Mixed-Grass Rangeland

Combined growing- and dormant-season pasture use has potential to increase herbage harvest without causing the undesirable shift in species composition that occurs with excessive utilization. The objective of this study was to determine the effect of summer clipping on winterpastures and winter clipping on summer pastures regarding standing crop, plant community composition, and forage quality. The study was conducted from 2003–2006 at the Antelope and Cottonwood Research Stations located in the mixed-grass prairie of western South Dakota. At each location, the experimental design was a randomized complete block with three replications that included 18 clipping treatments arranged as a split-split plot. Whole plots consisted of four summer clipping dates (May–August). Subplot treatments were two clipping intensities (clipped to residual height to achieve 25% or 50% utilization). Sub-subplots consisted of two winter clipping intensities (unharvested or clipped to a residual height to achieve a total utilization of 65%). Two winter control treatments were arranged in the subplot and split into two clipping intensities of 50% and 65% utilization. Winter biomass for the May 25% clipping treatment was similar to winter biomass for winter-only clipping. No increase in forage quality resulted from summer clipping compared with winter clipping. Three consecutive yr of combined growing-season and dormant-season defoliation to 65% utilization resulted in no change in functional groupcomposition compared with ≤ 50% utilization treatments. Clipping in June resulted in reduced midgrass biomass at both stations and increased shortgrass biomass at Cottonwood. Results suggest that producers could combine growing and dormant-season grazing to increase the harvest of herbage on mixed-grass prairie, but should change season of use periodically to avoid an undesirable shift in plant composition