Where, R is the radius of this octagonal monopole antenna in
’cm’ and S is the lenght of the feed line in ’cm’ as be shown in
figure 2. The factor k has a significance of an effective
dielectric constant, as the configuration is printed on a
substrate. From [4], The empirical value of k = 1,15, for FR4
substrate with εr = 4.4 and h = 1,59 mm, approximates the
lower resonance frequency for VSWR = 2 within 10%.