Mathematical analyses have been made of the field intensity existing at close proximity to both a terminated transmission line within a shielded room and an injection loop and are presented to permit the determination of such field intensities in terms of distance from the source of excitation and the exciting voltages. Experimental determinations have verified the accuracy and correlation of measurements made by both methods up to a frequency of 10 megacycles. Further investigations of the action of a terminated transmission line operated within a shielded room have indicated that the accuracy of field intensity below the line with respect to the frequency employed is a function of room size, line length and perfection of termination. For a room 22 x 14 x 12 feet in height, using a relatively small diameter transmission line, computed field intensities may be expected to be accurate within experimental limits up to a frequency of 15 megacycles but beyond this frequency, certain not completely determined conditions may introduce errors as high as 70% due to the existence of relatively sharp resonances. It is shown that pure resistive terminat on of a small diameter transmission line within a shielded room is inadequate to completely eliminate all standing waves at the higher frequencies.
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