Techniques for time‐resolved x‐ray diagnostics will be reviewed with emphases on systems utilizing x‐ray diodes or scintillators. System design concerns for high‐bandwidth (≳1 GHz) diagnostics will be emphasized. The limitations of a coaxial cable system and a technique for equalizing to improve bandwidth of such a system will be reviewed. Characteristics of new multi‐GHz amplifiers will be presented. An example of a complete operational system on the Los Alamos Helios laser will be presented which has a bandwidth near 3 GHz over 38 m of coax. The system includes the cable, an amplifier, an oscilloscope, and a digital camera readout.