 Height Obstacle Tree conditions: 40 + 10 ft growth (T and G) Frequency band: 6 GHz 452.7 Midpath Fresnel (0.6) 314.6 = 42 ft 501.8 Figure 9.5 Practice path profile. (The x-axis is in miles, the y-axis is in feet; assume that K = 0.9; EC is the earth curvature and F is the dimension of the first Fresnel zone.) 9.2 RADIO SYSTEMS The profile now gives us two choices, the first based on the right-to-left line and the second based on the left-to-right line. However, keep in mind that some balance is desirable SO that at one end we do not have a very tall tower and at the other a small, stubby tower. Nevertheless, an imbalance may be desirable when a reflection point exists at an inconvenient spot along the path SO we can steer the reflection point off the reflecting medium such as smooth desert or body of water. 9.2.3.4 Path Analysis or Link Budget 9.2.3.4.1 Introduction. A path analysis or link budget is carried out to dimension the link. What is meant here is to establish operating parameters such as transmitter power output, parabolic antenna aperture (diameter), and receiver noise figure, among others. The link is assumed to be digital based on one of the formats discussed in Chapter 6 or possibly some of the lower bit rate formats covered in Chapter 19. The type of modulation, desired BER, and modulation rate (i.e., the number of transitions per second) are also important parameters. Table 9.2 shows basic LOS microwave equipment/system parameters in two columns. The first we call "normal" and would be the most economic; the second column is titled "special," giving improved performance parameters, but at an increased price. Diversity reception is another option that may wish to be considered. It entails greater expense. The options in Table 9.2 and diversity reception will be addressed further on in our discussion. 9.2.3.4.2 Approach. We can directly relate the desired performance to the receive signal level (RSL) of the first active stage of the far-end receiver and that receiver's noise characteristics. Let us