The derivation of an analytic formula for the impedance of cylindrical and helical antennas in cold magnetoplasma is outlined. The method used is a conventional one reducing to integration of a three-dimensional integral involving the Fourier transforms of the current distribution and tensor Green's function. It is shown that the impedance decomposes into three parts corresponding, respectively, to the axial and circumferential components of current, and a mutual impedance depending on both current components. The explicit formulas are in the form of one-dimensional integrals suitable for machine computation. The integrands are made up of many simple terms, and for brevity only the impedance terms referring to the axial current are written out explicitly.