Народ, есть следующая конструнция для работы на мощностях до 5 кВт.

To fit the unbalanced coaxial cable to the balanced
load, a quarter-wavelength balun
was used. The balun was made from a copper sleeve
of 13-mm diameter and placed over the semi-rigid
transmission line with a diameter of 3.6 mm. This
sleeve, together with the outer jacket of the semi-rigid
transmission line, formed a shortened quarter-wave
line tuned to the resonance frequency of the coil. The
diameter ratio between sleeve and outer jacket of the
semi-rigid cable of about 3.6 caused a coaxial-line
impedance of 77 Ohm and minimized losses in the coaxial
line. The impedance looking into the open end
of this line was greater than 100 kOhm. The end of the
outer conductor of the semi-rigid cable was isolated
from the part of the line below the sleeve. This reduced
losses caused by currents on the shield of the
semi-rigid cable.

In addition to the balun, we used
a parallel resonance circuit for further suppression of
standing waves on the outer jacket of the semi-rigid
cable. The trap circuit was constructed by bending the
semi-rigid transmission outside the balun to a single
loop of 60-mm inner diameter. A capacitance was
soldered in parallel to his loop inductor in order to
form a RF trap

Что можно почитать по теории таких конструкций (годится и на английском языке)?
Просто в большинстве упоминаемых на форуме книг рассматриваются конструкции достаточно слабомощные. Рабочая частота 300 МГц, так что простые полосковые конструкцию тоже не получаются.