 the antenna P/ = radiation intensity produced in all directions by a hypothetical loss-less isotropic radiator This gain may also be defined as the ratio of radiation intensity produced by the antenna to that produced by a loss-less isotropic radiator with the same input power. The expression G(A, 0) is called the gain function to distinguish it from its maximum value Gm, which is called the gain of the antenna, as shown by the following equations: (3.3) (3.4) Pt = NP; (3.5) G(0,0) = nD(A, 0) (3.6) Note that: Good directivity allows dense packing. A large diameter gives better directivity. Although high gain antennas are better for radio system performance, a higher gain would mean better directional use leading to a finer path of the radio signal. This has an implication during installation, as the antenna needs to be more accurately aligned. Microwave Link Planning Front-to-Back Ratio The front-to-back ratio (FBR) is defined as the ratio of the power radiated in the desired direction to the power radiated in the opposite direction: power radiated in desired direction (3.7) power radiated in opposite direction The FBR becomes quite important when doing an interference analysis. The higher the front-to-back ratio, the better it is as the interference from the side lobes will be less. The FBR changes if the frequency of operation of the antenna system shifts. Its value decreases if spacing between the elements of the antenna increases. The FBR depends on the tuning conditions of the electrical length of the parasitic elements. Typical values of the FBR are 35-50 dB. The higher the gain of the antenna, the higher is the FBR. However, an increase in the value of the FBR can be achieved by diverting the gain of the opposite direction (i.e. backward) to the forward or desired direction. This is done by adjusting or tuning the length of parasitic elements. Hence a higher value of FBR is achieved at the cost of sacrificing gain from the opposite direction. In practice, for receiving purposes more adjustments are made t