Font Size: 

The raise of the gain of cylindrical spiral antenna (CSA), which is excited in axial radiation mode, is usually reached by extension of axial length of the spiral [1]. However CSA gain at large (more than 15) number of coils depends on magnitude of the angle of the spiral winding [2]; when the angle of winding is close to 14°, it is increased practically linearly with growth of coils number. Increasing of CSA gain of limited axial length is received by the putting of the metal cylinder inside of a spiral [3]. When common length of antenna is equal 1.58λ, gain is more than 13 dB.