An Antenna Impedance-Measuring Instrument

This paper describes an antenna impedance-measuring instrument of the indicating type, designed to have a small capacitive loading effect when connected directly to the terminals of an antenna. The model constructed operates at freqencies up to 30 mc and has a loading effect no greater than that of a conducting sphere 1.5 inches in radius. It appears feasible to extend these limits considerably merely by mechanical refinement. The smallness in effective size is obtained by isolating those conducting components of the instrument which are not part of the RF circuit and by operating the antenna under test as a receiving antenna so that the instrument does not have to contain a signal generator. No power or control wires are connected to the instrument, and it is possible for the operator to remain outside the immediate field of the antenna during the measuring process.