The impedance of a small loop in magnetoplasma is derived for the cases of magnetic field normal to and parallel to the plane of the loop. The quasi‐static and uniaxial approximation methods are used, and an argument is given to justify the uniaxial approximation as the more desirable method. The results of the theory are given in analytic form and are evaluated numerically and presented graphically. The loop impedance is seen to be much less plasma‐dependent than the impedance of a short electric dipole. It is shown that the small loop can be an efficient radiator under certain plasma conditions. The results of laboratory measurement of loop impedance in magnetoplasma are also given for the cases of normal and parallel orientation of the magnetic field with respect to the plane of the loop. The laboratory plasma is generated by using a brush‐electrode configuration. The measured impedance is compared with the theoretical predictions, and good agreement is shown for the perpendicular orientation. Quantitative agreement with the theory is not as good for the case of parallel orientation, but much of the gross impedance behavior is verified for this orientation, particularly the fact that the impedance is relatively plasma‐dependent.

This study co mmences by demonstrating the important role played by the dispersion surfaces in the determination of the far fi e lds of an infinitesimal dipole in a lossless, cold magn eto· ionic medium. The dispersion surfaces are then classified, according to th eir shapes, for differe nt ranges of the plasma parameters. A comprehe nsive group of radiation patterns is the n given including far fi elds for eac h of the fourtee n classified range s of the plasma parameters.

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One of the most promising approaches towardanunderstanding of the operation of the logarithmic periodic antennas is based upon the consideration of these antennas as locally periodic structures whose period varies slowly, increasing linearly with the distance to the point of excitation. This concept, first proposed by Wayes, Deschamps and Patton', forms the basis forthe present analysis of the near fields on the conical logarithmic spiral antenna.In this light we will compare the propagation constant measured along the surface of the narrow-arm conical antenna to the known propagation constants associated with the cylindrical bifilar helix. To illustrate the parameters involved, one cell of a cylindrical structure has been superimposed upon a corresponding cell of a wire version of the conical structure in Figure 1.The Brillouin diagram shown in Figure 2 is a convenient display of the frequency variation of the propagation constant on the surface of the cylindrical helix. In this particular figure the free space propagation constant k is equal to 2 T / A, , "a" is the radius and the spiral angle o ( is the complement of the pitch angle, hence the vertical axis is the pitch distance ( o r cell size) normalized to the wavelength in free space. The horizontal axis is the pitch normalized to the equivalent "guide" wavelength, i. e., wavelength associated with the nth space harmonic on the structure, and hence is proportional to the phase constant along the surface of the structure. It can be shown thatthe line 1-Pa/tan 4 is a boundary for regions of the diagram that correspond to slowwaves, normally associated with bound surface waves, and fast waves associated with complex propagation constants and radiation in the open structure2. It has also recently been shown that the propagation constant may be complex within the slow wave region, in the neighborhood of the above b~u n d a r y~.~.-137 -