r_helix 10[mm] "Helix radius"
a_pitch 15.7[mm] "Helix pitch"
n_turn 5 "Number of turns"
h_ground 10[mm] "Ground plane thickness"
l_pin 3[mm] "Pin length"
f_normal 385[MHz] "Frequency at normal mode"
lda_axial pi*2*r_helix "Wave length at axial mode, air"
f_axial c_const/lda_axial "Frequency at axial mode"
f0 f_normal "Frequency in sweep"
lda0 c_const/f0 "Wavelength in free space"