The antenna has
poor efficiency at the 80- meter Band. However I believe that
the efficiency may be improved if perimeter of the antenna and
diameter of the tube (from which the antenna made of) increase
in twice times. Matching the antenna with the coaxial cable is
doing by moving the inner bridge.
Antenna has sharp matching.
Tuning capacitor is connected by Butterfly circuit. Counterpoises
connected to ground terminal of the transceiver could be improved
the antenna efficiency. Device “Artificial Ground” could improve
the efficiency of the antenna as well.
Inductor (OD- 9- mm, 9 turns of 2-
mm (AWG- 12), length 25- mm) connected between coaxial shield
and antenna could expand the working range from 3.44- MHz to 28.75-
MHz and improve SWR but not for 15- meter Band. Additional matching
may require at the band. However in my case I have got matching
at the 15- meter just increased length of the feeding coaxial
cable on 1.85- meter.