This paper describes t he design and the performance of a multiple-wire delta antenna developed for use with high output impedance, vert ical-incidence ionosphere sounding equipment. Graphs are presented showing the terminal impedance of this antenna over the separating frequency range (1 to 25 megacycles) , using various lengths of open-wire transmission line. The results of pattern measurements using model tech niques are given , showing the expected radiation characteristics of the full-scale antenna. A practical test of the comparative merits of the antenna is described in which ionosphere records obtained by the u se of this antenna are compared with those obtained by the use of a larger antenDa developed p reviously.
An electronically scanned antenna array is described . It consists of a broadside array of seven Yagi elements spaced 1.4 wavelengths apart. Each element antenn a is connected to a preamplifier-converter. Each conver ter is connected to a local oscillator differing by 20 cis from that connected to the converter for the adj acent clement. All oscillators are locked in phase. The converter outputs are co nnected to a common IF amplifi er. This arrangement produces a 5.8-degree-wide beam swept over a 41. 8-degree azimuth sector at a rate of 20 scans per second. The system operates at 40.92 Mc/s. The output of the system is displayed on an oscill oscope, and data on the direction of arrival and character of a distant VHF signal are presented vis ually.Sample reco rds of signal compone nts propagated by ionospheric scatter , meteor trail r efl ections, and sporadic-E layer are cited .
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