Antenna assembly and multiband stubby antenna

Abstract

A preferred compact antenna assembly of the invention includes a nonconductive hollow core plug. The core plug has a recessed pattern on an outside surface into which a helical radiator is wound. An end portion of the helical radiator extends through a hole in the core plug to contact a center radiator extending in the hollow portion. A cover covers the helical radiator. Preferably, the entire assembly is configured to snap-fit together and to a device. The cover and core plug may snap-fit together. The bottom of the core plug may define a mount and the center radiator may be exposed from the mount as a device contact. The center radiator is also preferably shaped to grab onto the helical radiator. The recess pattern and hole on the core plug allow formation of the helical radiator having the exact pitch defined by the recess pattern by inserting a wire into the hole and applying pressure to the wire while rotating the core plug and wire vis a vis each other to wind the wire into the recess pattern. The cover and core plug are then attached. The helical radiator preferably includes separate lower, middle and upper sections respectively having separate lower, middle and upper pitch angles. The lower pitch angle defines a length of the helical radiator which determines resonance in an upper frequency band. The entire length of the helical radiator determines resonance in a lower frequency band. The middle pitch angle defines a length that acts as a choke with high impedance at the upper frequency band and low impedance at the lower frequency band. A cover is attached to the core plug to cover the helical radiator. An electrical contact contacts the helical radiator and is exposed from the core or cover for contact to a device.