# Effect of Buildings on the Radiation Characteristics of MF Broadcast Antennas
## 4 Discussion  
By examining the patterns in Figures 4 and 5, one may conclude that the height of a building situated in the vicinity of a radiating monopole may affect the radiation pattern of the antenna significantly for \(H\geq 0.3\lambda\), i.e., \(H\geq 60\) m for \(f=1494\) kHz, a height that corresponds to a building with 12 stories, provided that each story is 5 m high. It may be readily verified that the blue dotted curve (\(H\approx 0.2\lambda\)) almost coincides with the black solid curve (the pattern in the absence of the building), whereas the patterns in the presence of a building with \(H\approx 0.3\lambda\) or \(H\approx 0.4\lambda\) deviate considerably from the omnidirectional pattern. The same remark holds for both distances (\(R\approx 0.5\lambda=100\) m and \(R\approx\lambda=200\) m) between the building and the antenna. Moreover, a comparison between Figures 4a and 5a may lead to the conclusion that the distance between the antenna and the building may affect the radiation pattern only when the height exceeds the critical value of \(0.3\lambda\). The impact of the length and width of the buildings on the antenna's radiation pattern was examined by comparing Figures 6 and 7, respectively, with Figure 4. The parameters used to produce Figure 6 were the same as those in Figure 4, except for the length of the building (\(L\approx 0.05\lambda=10\) m in Figure 4, \(L\approx 0.3\lambda=60\) m in Figure 6), whereas the parameters that appear in Figure 7 are the same as those in Figure 4, albeit the width of the building is six times greater (\(W\approx 0.05\lambda=10\) m in Figure 4, whereas \(W\approx 0.3\lambda=60\) m in Figure 7). Figures 6 and 7 indicate that the length and the width of the building do not seem to have a significant impact on the radiation pattern of the antenna, as long as the height of the building is kept below a critical value; the blue dotted curves in Figures 4, 6 and 7 (all of which correspond to \(H=20\)\(m\approx 0.1\lambda\), whereas \(L\) and \(W\) differ according to the captions) are all the same, and they practically coincide with the omnidirectional shape. As the height increases (red dashed curve of Figures 4, 6 and 7, i.e., \(H=50\)\(m\approx 0.25\lambda\)), the pattern deviates slightly from the omnidirectional pattern; however, \(L\) (W) has a negligible effect on the pattern, as may be readily verified by comparing the red dashed curve in Figure 6 or Figure 7 with the curve in Figure 4. However, for \(H\geq 0.3\lambda\), the radiation of the antenna deviates considerably from the omnidirectional behavior, as indicated by the blue dashed-dotted curves in Figures 4, 6 and 7. In this case, the effects of the length and the width of the building are more pronounced. For the width in particular, a comparison between the blue dashed-dotted curves in Figures 4a and 7a shows that the two patterns  
Figure 9: Radiation patterns of the array in free space (black, solid curve) and in the presence of a building with \(L=50\) m \(\approx 0.168\lambda\) and \(W=10\) m \(\approx 0.034\lambda\). Three different heights \(H\) are considered (dashed and dotted curves, as indicated at the upper right corner). The distance between the antenna and the building is \(R=100\) m \(\approx 0.336\lambda\). (**a**) \(\varphi\)-plane and (**b**) \(\theta\)-plane. differ slightly from each other, apart from the deviation of the omnidirectional shape. It should be noted that several patterns were produced by varying the parameters of the configuration in order to ensure that the above remark held in a vast number of cases. All the results support the aforementioned conclusion and they are omitted for the sake of brevity.