6.1 Thick Monopoles

I only know of two experimental studies of the monopole that cover a wide range of radius and height values. The first was published in 1945 by Brown and Woodward [1, pp. 4 6:4 9] and in the 1960s by students of R. W. P. King [2]. Figure 6.1 illustrates two different ways to drive a thick monopole. Figure 6.1(a) is a coaxial cable below the ground plane with the center conductor extended to make the antenna. This method was used in both sets of measurements. Figure 6.1(b) shows a relatively narrow coax with its center conductor passing through to the base of a thick cylindrical antenna. This method was also used by Brown and Woodward, although the details of the feed geometry are not given.

Figure 6.1: Two monopole feed arrangements.

The data in [1] is given as curves in two different formats. The resolution for h _m < 0.1 ? for the resistance curves is not very good, but one can draw some general conclusions. For the straight-through coax feed system of Figure 6.1(a), the tighter the coax is, the smaller the reactance magnitude is. The feed system of Figure 6.1(b) has a much lower reactance magnitude than the straight-through cases, and also appears to have lower resistance. The data in [2] is given both in curves and tables, and I use it to verify the modeling results of the next section.