A portable 50 MHz transmitter capable of 15 kW peak rf power output at up to 5 percent duty cycles is described. The transmitter and a system synchronizer, also described, are combined with a frequency-coherent receiver, an on-line minicomputer processor with oscillograpic display, and a novel collinear antenna to provide a highly portable VHF Doppler radar system. The system, complete with 5-degree azimuthal beamwidth antenna, weighs about 250 kg, and can be installed in remote locations in a few days. It has been used successfully in studies of equatorial and auroral ionospheric irregularities during the past several years.

This report describes the interfacing and programming of a minicomputer for Doppler spectrum analysis. The interfaces include analog-to-digital converters for data input and digital-to-analog converters for display of the Doppler spectra on an XY oscilloscope. These interfaces are contained in the computer chassis which has the dimensions of a suitcase. The software that is included in this report is specifically written for 64 point Doppler spectra. The Fast Fourier Transform algorithm is used in the analysis, and the time required to transform a 64 point array is 23 milliseconds. Control of the spectral analysis program is by means of 16 data switches on the front panel of the computer.

The purpose of this research project was to develop a radar technique to detect the presence of flying birds potentially hazardous to aircraft near airport runways; to distinguish them from other radar targets; to estimate the size and number of birds in order to assess the hazard. The motions of a bird in flight are characterized by a distinctive velocity spectrum that can be detected by radar. These 'aural signatures' were identified by Doppler technique and verified by visual sightings. This report provides a description of the analysis techniques, compares range-gated to nonrange-gated systems and also conventional and Doppler radars. A discussion concerning modification of a typical system to a Doppler system is included. A method of determining the actual number of birds in the target volume is discussed. The report also includes a scene-by-scene description of a film presentation made to more fully quantify the Doppler technique. (Author).