AN/TRD-15/23 Direction Finding Set
1-4. Purpose and Use
a. Direction Finding Set AN/TRD-23(*) is a radio direction finder system which accurately detects and displays the azimuth bearing of radio signals in the 1.5- to 20.0-megahertz (MHz) frequency range on either a primary or secondary equipment console. Both may be put into service to locate separate signals using the same antenna array.

b. The primary function of the system is to obtain bearing information (on) communication signals picked up by the antenna array. This information is displayed on a cathode-ray tube which is continually sensed by electronic circuitry.
c. Functionally, Cabinet, Electrical Equipment CY-6691/TRD-23A (primary console) and Cabinet, Electrical Equipment CY-6690/TRD-23A (secondary console) are identical and can be used for direction finding on different signals simultaneously. The No. 1 receiver in each console is always required for direction finding. (Excerpted from: Technical Manual TM 11-5825-231-10 Headquarters, Department of the Army February 1973)
