A multi-filar helical antenna comprising a helical radiating element extending along a longitudinal axis, comprising an elongate body having a free first end and a second end opposite the first end and coupled to a feeding port, and a tail member, extending away from the body at the second end. The tail member has a geometry that is selected for modifying at least one of an impedance of the radiating element, and broadening the antenna's resonance bandwidth. The radiating element may comprise a positioning member extending away from the second end along a direction substantially parallel to the axis. An end portion of the positioning member is secured to an electrically conductive surface in connection with the feeding port. The second end is positioned at a given distance above the conductive surface and the radiating element is fed through the feeding port at the given distance above the conductive surface.