Antennae for ultra-high frequencies. II

[See Abstr. 1944B02151]. A general study of u.h.f. aerial problems, together with a critical discussion of the mathematical results obtained by various authors. The concept of back-e.m.f. is used to calculate radiation resistance, and it is shown how the results agree with those obtained by more usual methods, and illustrate the nature of the fields close to the aerial. Aerials of finite cross-section are considered in detail. The radiation resistance is shown to be independent of thickness for small diameters, justifying the ellipsoid approximation; the variation of resistance along the wire is also determined, and is shown to agree reasonably with experimental results over a range of conditions. End effects of cylindrical aerials are examined, taking account of the charges, as well as the finite current at the end of the cylindrical portion. The results of Oseen, Halleacuten, King and Schelkunoff are discussed and related, and their approximations made clear. It is concluded that those derived for spherical, spheroidal and biconical aerials are trustworthy; those for cylinders of finite cross-section are less reliable.