Bihelical traveling-wave tube with 50-decibel gain at 4000 megacycles

The construction and performance are described. Values of 1400 V and gammaalpha = 1.5 approx. were chosen, a focusing field of 600 G being required. Curves are shown for the variation with frequency and/or operating conditions of the small-signal and saturation gains, the power output (about 6 W maximum), the matching (v.s.w.r. less than 1.4 from 3800 to 4400 Mc/s) and the noise factor (about 25 dB with a partially shielded gun).