The design of air-core inductance coils of minimum weight for a given inductance and resistance

ANYONE familiar with the design of air-core inductances knows, that for a given resistance, the size and weight of the coil rapidly increase as the inductance is increased. Though the increased cost due to this increase in weight may not be of great importance, it is evident in many types of apparatus in which such coils play an essential part, as in portable radio sets, that both weight and size must be reduced to the minimum possible.