Abstract: Disclosed is a microwave detector for giving an indication of the presence of microwave energy at either X-band or K-band frequencies. It utilizes a common horn and waveguide resonator with four diodes. A divider separates the waveguides into two compartments and the pairs of modulator and detector diodes are in respective compartments. The diode pairs extend at right angles to each other across the short dimension of the respective compartments and the horn and antenna are oriented so that the diode pairs both extend substantially at a 45.degree. angle to the vertical.