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During the past four years, experiments using high power, high frequency transmitters have demonstrated that significant modification of the F region of the ionosphere can be effected. This paper illustrates that relatively low power, creating power flux densities in the F region of the order of 1 μw m−2, can also produce significant modification in the ionosphere. Such low power illuminations create field-aligned ionization irregularities that produce a significant scattering cross section in the modified ionosphere. It permits propagation of VHF signals over selected long distance paths that could not be used by natural means.

A considerable decrease of the area of projection of the blind spot, shortening of the adequate optic chronaxia and reduction of the rheobase were observed in 2 persons at the end of a 10-minute period of micro-wave exposure (λ=10 cm with the power flux density of 1 milliwatts/cm2).

This paper presents the results of preliminary studies to determine the feasibility of using synchronous stationary satellite systems for the distribution of video and radio program material to conventional broadcast stations. Two systems concepts, differing because of constraints imposed by selection of operating frequencies but meeting the same channel capacity, performance, and reliability requirements, were found technically feasible. One system operates in the shared 4 gHz band and uses a novel modulation scheme to keep the spectral power flux density within bounds. The other system operating at 5 gHz uses a novel multiple-beam antenna concept which keeps the radiation from spilling over neighboring countries.

The dispersion relation for backward‐stimulated Brillouin scattering shows that near threshold the most unstable reflected wave rapidly outruns a laser driven underdense plasma. Laser energy absorption may, however, be affected at power flux densities above 1015 Ws/cm2 for 1.06 μ radiation.

A theoretical analysis of the operation of the depletion layer transducer has been made, taking into consideration both the backing and the delay medium. This transducer differs from the conventional type in that the boundaries of the piezoelectrically active region vary with applied voltage. For plane elastic waves in a semi‐infinite piezoelectric semiconductor, it is possible, under certain restrictive assumptions presented here, to solve the piezoelectric equations, including the effect of moving boundaries. For the case of small signals, the time‐average sonic power flux propagating away from the depletion layer has been found as a function of drive amplitude, frequency, layer thickness, and backing distance. From the sonic‐flux expression, conditions on the layer thickness and backing distance can be deduced which lead to optimum operation at a given frequency. Under favorable conditions, an intrinsic bandwidth of 70% is possible. Some remarks on the mechanism and extent of harmonic production are al...

It is shown that the solution given in a previous paper for the reflection at a ferrite boundary in a rectangular waveguide is invalid in a certain region because it implies a finite power flux into the waveguide walls. This flux can be taken care of by means of Bresler's surface waves, which can propagate in the anomalous region, and which were postulated in order to resolve a thermodynamic paradox. Their reality when the ferrite is lossy, however, requires further elucidation.