and structural temperatures gradient variations will be comparable. If waveguide lengths are adjusted to the average temperature, the residual changes as a function of radius would be: If uncompensated, this variation would result in a relatively large peak loss of efficiency for aluminum waveguide construction (negligible for composites). A frequency change can partially compensate by changing the effective electrical length of the waveguide. For a 5 dB taper and selecting 35C° as the nominal correction value, the peak efficiency loss is reduced to 0.5 percent. At 10 dB taper it is 0.4 percent. The required shift in wavelengths is only 1/10^, representing 245.0 kHz at a 2.45 GHz nominal operating frequency. Since the average loss over the diurnal cycle is of the peak value, the net impact on the system efficiency budget is negligible. 6.6.3 WAVEGUIDE ATTENUATION The attenuation in a waveguide is given by: The MPTS guide has a , and . The top and bottom walls account for 0. 0019 dB/m and the sidewalls account for 0. 0072 dB/m. in practice. The 0. 0091 dB/m is a theoretical value based on = 0. Consequently, the surface roughness contribution is 2. 84 times greater than the broad wall attenuation. The total attenuation
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