An impedance simulator having the capability of simulating the operational mpedance characteristics of a whip antenna in open field throughout a given frequency range. The simulator includes a cylindrical chamber of conductive, non-magnetic material coated on the interior surface with a lossy ferrite material. Coaxially mounted on the interior of the chamber is a coaxial conductor having at one end thereof a coaxial connector. The other end of the coaxial conductor has the center conductor thereof extending beyond the end of the outer conductor. This end of the inner conductor has mounted thereon a metallic disk lying in a plane perpendicular to the axis of the coaxial conductor. The utilization device, such as an r-f power source is attached to the coaxial connector. The assembly presents to the utilization device an impedance similar to that of a whip antenna in open field.
A test apparatus is disclosed which is particularly adapted for testing survival-type radio transmitters in the field. The apparatus includes an enclosed metallic test chamber into which the antenna of the radio transmitter is placed. A movable load carriage within the chamber applies a load to a predetermined point on the antenna which results in simulating in the test chamber the radio frequency absorption/reflection characteristics of the antenna in free space. A direct measurement of the radio frequency energy absorbed by the load is thus indicative of the performance of the radio transmitter and its antenna in free space.
An antenna coupler for coupling a portable radio to an auxiliary antenna to provide transmission and reception through the auxiliary antenna. The antenna coupler includes an outer tubular conductor and an inner tubular conductor coaxially disposed within the outer tubular conductor. An end cover having an antenna opening is secured to one end of the tubular conductors. The radio and auxiliary antenna are placed in a coupled position by inserting the on-board antenna into the inner tubular conductor. The coupled, on-board antenna and inner tubular conductor form a close-coupled transmission line with the antenna functioning as the central conductor and the inner tubular conductor functioning as an outer conductor of the transmission line. The inner tubular conductor is conductively connected to an impedance matching circuit and RF connector for providing impedance matching and interconnection with the auxiliary antenna. In addition, the outer tubular conductor is grounded to the radio collar to provide a common ground, and functions as the outer ground or shield for the close-coupled transmission line.
