6356

This tube is designed for use as a noise source in super high frequency (SHF) measurements. It is constructed for use with the RG-49/U and RG-50/U waveguides to provide noise in the 3.7 - 7.6 cm waveband. When used in the standard mount assembly, it functions as an untuned termination over the entire recommended transmission bandwidth of the guide. The run-start switch shown in the typical circuit provides the high voltage surge or spike necessary to initiate the discharge. In the start position, current passes through the filament at the cathode end of the tube preheating the filament and assisting in starting the discharge. As the switch is released to the run position, a high surge voltage appears momentarily across the tube, caused by the col- lapse of the magnetic field in choke ‘‘L". This high voltage initiates the discharge in the tube which is then sustained by the power supply voltage and stabilized by the re- sistance R2. External power is no longer supplied to the filament once the discharge is established. Filament tem- perature is maintained by the tube current and is evi- denced by a hot spot on the filament structure. OPERATING CHARACTERISTICS The use of pure inert g