Abstract: A photoconductive antenna modulator which optically modulates a radio frequency carrier signal from a dielectric waveguide antenna is disclosed. A photoconductor film is placed in proximity with the dielectric waveguide antenna such that the radio frequency carrier signal from the antenna must be conducted through the film when it is radiated into space. The carrier is then optically modulated by variably illuminating the photoconductor film with light which has wavelengths near the photoconductor film's spectral region of photoconductor sensitivity, which decreases the photoconductor film's transparency to the radio frequency carrier signal. By varying the strength of the illumination on the photoconductor film, one is able to optically modulate the radio frequency carrier signal propagated through the photoconductor.

Abstract: A method for detecting the polarized potential of a buried pipe which is cathodically protected by rectified alternating current impressed upon the pipe. Each rectified protection current is periodically pulsed to an off state for a precise pulse duration and pulse period which are integral multiples of the period of the alternating current. The potential between the pipe and a reference electrode at the test site is sampled and analyzed to detect the polarized potential. It is analyzed to find the area under the portion of the waveform during which no off pulses are present and to use that area to detect the on potential. The area within the off pulses, after reactive spikes are eliminated, is substracted from the on potential area to determine the IR drop potential. The IR drop potential is then subtracted from the on potential and the difference is displayed as the polarized potential.