The X347A is a WR-90 Rectangular Waveguide Noise Source. The X347A uses an argon gas discharge tube to produce a 15.7 dB ENR over a frequency range of 8.2 to 12.4 GHz. Connections are via UG-39/U waveguide flanges. The X347A produces a flat, broad spectrum noise for use with a 340B or 342A Noise Figure Meter to measure the noise figure of radar and other microwave receivers.