Abstract: A bifilar helical antenna which will radiate or receive in the backfire mode. The antenna consists of two interlaced helixes fed at the tip. Each helix is fed by a transmission line with energy of equal amplitude but 180.degree. out of phase. Optionally the helixes may be connected to a ground plane at the far end for mechanical stability. For the same reason an insulating right cylinder may be used to support the helixes. The two helixes have such a diameter and such a pitch or pitch distance that the currents flowing from their terminals to the far end are out of phase while the currents flowing in the reverse direction are in phase to provide a fast pseudo wave structure.