impedance
of the antenna at 10 meters is close to 40Ohms, and50Ohms coaxial
cable can be used for feeding of the antenna at the range. However,
physical length of antenna consisting of another following section
plus the previously section (or sections) is less then λ/4.
Inductors of the traps work as a lengthening spools for the proper
section. Input impedance of the antenna working at lower then
10 meters range is less then 30 Ohms in the theory, but in practice,
the input impedance for 15 and 20 meters range is close to 40
Ohms because losses in antenna parts and antenna

ground.
So, a 50Ohms coaxial cable can be used for feeding of the antenna
at all of the ranges. For a proper work a vertical trap antenna
must have several counterpoises for every of operation ranges,
especially for low amateur HF ranges 40, 80 and 160m.
Antenna
input impedance. Dipole Trap antenna: Morgan trap antenna
[1] was done as a dipole.
It is known, that a λ/2 (physical length) dipole antenna
has input impedance close to 75 Ohms, see Figure
3A. A shortened by a lengthening spool dipole
