REFLEX OSCILLATORS 607 



the 2K50. In fact, the diameter of the grid wire can be made but little 

 smaller. Thus, in the 1464XQ the grid is relatively coarse compared with 

 that in the 2K50. This results in a reduced modulation coefficient and 

 hence in less efficiency. 



In going to .625 cm., resonator losses are of course greater. The surface 

 resistivity of the resonator material varies as the square root of the fre- 

 quency. Surface roughness becomes increasingly important in increasing 

 resistance at higher frequencies. Further, in order to provide means for 

 moving the diaphragm in tuning, it was necessary in the 1464XQ to use a 

 second mode resonator (described later) and this also increases losses over 

 those encountered at lower frequencies. 



Development of the 1464XQ was stopped short of completion with the 

 cessation of hostilities. However, oscillation in the range .625-. 660 cm. 

 had been obtained. The power output varied from 2-5 milliwatts between 

 the short wave and long wave extremes of the tuning range. The cathode 

 current was around 20 ma, the resonator voltage 400 volts. The tube 

 operated in several repeller modes in a repeller voltage range to — 180 volts. 



Figures 97 and 98 illustrate features of the 1464XQ oscillator. Figure 98 

 is a scale drawing of the resonator and repeller structure. The electron 

 beam is shot through two apertures covered with grids of .6 mil tungsten 

 wire. These grids are 80% open and are lined up. The aperture in the 

 grid nearest the gun is 23 mils in diameter and the second aperture is 34 mils 

 in diameter. The repeller is scaled almost e.xactly from the 723A 3 cm. reflex 

 oscillator. A second mode resonator is used. The inner part, a, of Fig. 98 

 is about the size of a first mode resonator. This is connected to an outer 

 portion, c, by a quarter wave section of small height, b, which acts as a 

 decoupling choke. The resonator is tuned by moving the upper disk with 

 respect to the lower part, thus changing the separation of the grids. The 

 repeller is held fixed. Power is derived from the outer part, c, of the reso- 

 nator by means of an iris and a wave guide, which may be seen in the section 

 photograph Fig. 97. There is an internal choke attached to the end of the 

 part of the wave guide leading from the resonator. This is opposed to a 

 short section of wave guide connected to the envelope, and in the outer end 

 of this wave guide there is a steatite and glass window of a thickness to 

 give least reflection of power. 



I. Oscillators for Pulsed Applications — The 2K23 and 2K54 



All the reflex oscillators described in the preceding sections have been low 

 power oscillators intended for beating oscillator or signal oscillator applica- 

 tions. Some limitation on the power capability of these oscillators in the 

 form previously described is set by the power handling capacity of the grids. 

 If the tubes are pulsed with pulse durations which are short compared with 



