W4TWW works on 160 meters since 1951, and has designed a lot of antennas. As a result of numerous experiments he stopped for coaxial INVERTED L (see figure), which gives a vertical polarization and allows you to work without additional adjustment throughout the range of 160 m At 1.8 MHz VSWR=1,3; NACC-1,1; 1998 kHz to 1.5. It should be noted that the SWR to some extent depend on the resistance losses in the ground system, i.e. the number and length balances. Three of the quarter-wave counterpoise.
To determine the adequacy of the grounding system can care SWR of the antenna after the rain - if the grounding system is effective, the change will be minor.
The antenna design is clear from the figure. Because of the high bandwidth with strict observance of dimensions does not require additional adjustment. If you need to change the resonance frequency of the antenna it can be done by changing the length of the horizontal two-wire line. You can build the antenna entirely of coaxial cable is to use coax instead of two conductive lines 300...450 Ohm. In this case, the braid and the core of the wire needs to be bridged as at the end of the antenna and the point A.
Literature
Publication: N. Bolshakov, rf.atnn.ru