Full 80m band inverted V antenna

80m band is good for local and dx contacts. The most common antenna there is a dipole or version of that, inverted V.

Dipole tends to be narrow in band width as seen in picture left below. It is impossible to cover the whole band with one setting.

But a dipole can be wide banded. By adding one resonator with suitable coupling to the antenna a similar effect as in double tuned band pass filters

can be achieved , see right hand picture above.

To proof the concept I built inverted V with the additional matching network. See attached schematic, picture, modeled results and measured results.

In testing the antenna I learned that wire sag broadens pass band up in frequency but at the same time worsens the average SWR.

By tightening the wires results were better. My feedpoint is now up 29m and element ends are up 18m.

The modeled and measured results are in good agreement.

Good quality components shall be used in order to avoid power losses and component damage.

Max legal power 1.5kW will generate 4kV peak voltage across capacitor C1. Reactive power tranfered is significant and

the capacitors shall withstand those kVAr's. Door knob or vacuum type of capacitor shall be used.

My coil was made from dia 1.5mm copper wire. In the next antenna I would use dia 2mm wire.

Resonator C1L1 measured resistance on band was 2.4 ohm, which means 0.2dB loss in 50 ohm system

The same wide banding principle can be used with normal straight dipoles and horizontal loops as well.

Component values may need to be changed however. Some examples are shown

Later it was discovered that capacitor C2 can be replaced with suitable length of coaxial cable.

This influences to the values of other components but gives similar performance when adjusted properly.

See example of that,

Also in this structure component values and wire dimensions depend on antenna height and shape.

Best results are achieved when modeling each case individually.

Pekka, OH1TV

18.10.2010

updated

12.12.2010