An ultra-wideband, nonperturbing, electric-field sensor is being developed that uses the linear electro-optic effect and is packaged in a suitcase-sized optical configuration. The methodology has been demonstrated on the optical bench with ZnTe and used to measure an applied electric field. The immediate goal is to demonstrate the sensor up to 4 GHz and apply it to unknown fields in a configuration using polished and coated ZnTe crystals. The unique features of the sensor include non-perturbing rf CW & pulsed (< 2 GHz) measurements inside of cavities, while preserving the amplitude, polarization, and phase content of the detected signal. Preliminary measurements reported here verify the crystal sensitivity of approximately 3 V/cm (1 mW/cm2) (into a 5 GHz bandwidth (BW) oscilloscope), and response linearity. Variations in optical configurations are compared on the basis of sensitivity.