This letter deals with an externally fed spiral antenna. This design is a slot antenna that exhibits a behavior similar to that of the center-fed Archimedean spiral antenna with an improvement in terms of polarization. The antenna radiates a circular polarization over a wide frequency band within a wide angular range. Moreover, the polarization radiated can be right/left circular or linear vertical/horizontal. A prototype has been manufactured and compared to the modeled antenna. Good agreement is shown between measurement and simulation results.