Disclosed are improved antenna structures, systems, and methods of manufacturing. In an embodiment, low-cost internal 2G/5G antennas have flat metal dipole construction, which can include a stiffener. External embodiments include quad dipole antenna structures, with broadside or corner arrays. Isolated multi-band center or end-fed dipole antennas can include single-sided PCB or metal-only structures, for operation with at least two distinct frequencies, and can provide RF isolation, such as with an RF trap or a Balun system. Embodiments of non-DC path or pass-through dual band antennas feature trap structures, along with discrete or distributed matching, and can provide a DC feed path for LEDs. Low profile and flat vertically polarized omni-directional antennas, such as for operation at 915 MHz, include an open slot driven cavity. Stacked 2G/5G antenna structures provide axial symmetry between quadrants. Improved construction methods and antenna structures include enhanced thin metal components and low cost, crimp-only construction methods.