creating multichannel systems consisting of one type parallel devices excited by a common power supply. As a result, it is possible to obtain strong directional radiation with an increasing maximum density of power flux being proportional to N 2 , where N is the number of elements in the system. The possibility of obtaining a stable phase of micro wave radiation (from pulse to pulse) achieved at a suf ficiently rapid growth of voltage U(t) across the diode forming the beam has been proven in the case of a rel ativistic backward wave oscillator (RBWO) with an electrodynamic system based on a round corrugated wave guide [1]. This system operates in the mode of superhigh radiance at a carrying frequency of 3.7 GHz and a relatively short microwave pulse of 3 ns. Stability of the radiation phase was also observed in the RBWO experiments at frequencies of 10 [2, 3] and 37 GHz [4,5]. Special devices were used in these experiments in obtaining a sharper front of voltage pulse in order to satisfy the theoretical condition of phase stabilization [5,6] (1)where T is the period of high frequency oscillations and C = [eI 0 Z/(2mc 2 )] 1/3 is the generalized Pierce parameter. In the latter formula, I 0 is the amplitude of an electron beam current; Z is its connective resistance with synchronous harmonics of the operating wave; e and m are the electron charge and mass, respectively; and γ 0 is the relativistic factor relating to diode voltage amplitude U 0 . Temporal factor T U is determined through the maximal derivative at the front of the volt age pulse and its amplitude,When condition (1) is satisfied, the growth duration of the beam current determined analogously to (2) cer tainly has a lesser magnitude [5]. The spectral compo nents from the front of a current then have weakly vari able phases in the frequency band of interaction [6]. Therefore, condition (1) is necessary when obtaining a fixed initial phase (ϕ in = const) of the microwave radi ation pulse from one pulse to another. For excitation of parallel generators, this phase should be the same in each pulse. With allowance for possible frequency deviation δω (ω is the carrying frequency) during time τ m from pulse to pulse, it is necessary to satisfy the con ditions (3) where δϕ in is the initial phase instability [5]. Due to the relativistic energy dependence of the electron velocity at small variations of the amplitude of pulse voltage (δU 0 /U 0 < 1%), conditions (3) can be fulfilled if the shape of the pulse is reproduced quite stable.In contrast to [1][2][3][4][5], the main aim of this work is to verify the possibility of the phase stabilization of microwave radiation in experiments with a generator frequency of 1-2 GHz and pulse duration τ m = 100T and without making the voltage impulse front sharper. In a frequency range of 1-2 GHz, it is worthwhile to use the RBWO construction based on a coaxial delay system (CRBWO) [7]. This is caused by the small dimensions of the electrodynamic system of the gen erator (D/λ < 1, L = 1.5λ, where D and L are the aver age di...