The QUAD antenna for tri-band
The figure shows the antenna element - type dual operating ranges of 20, 14 and 10 m Contour L1С1 configured to frequency of 15 MHz, the circuit L2C2-28.8 MHz. The antenna has a reduced size in the range of 20 m, the full dimensions of 14 m and elongated by 10 m To produce resonance tuning elements are: 20 m - C1 and L1, 14 m - C1 and L2, 10 m - C2 and L2.
In the design of VK2AOU antenna is made of copper wire. Coils are wound copper wire on the frame diameter: 37 mm winding Length L1 - 16, L2 - 18, and L3 - 9 mm L1 contains 7 coils L2 and L3 - 4 loop. The distance between the coils shown in the figure.
According to VK2AOU antenna had an SWR of 1 on 14,15 MHz to 1.3 21.3 MHz and 1.5 28.6 MHz.
DJ2UT have produced such an antenna made of aluminum tubes, inside which is placed coaxial cable segments, performing the role of capacitors C1 and C2.