Wideband reception installation - has non-tunable active antenna, and cable length shorter than eighth of wavelength

摘要

The frequency band is divided in several channels, and a parallel resonant circuit, tuned to the received channel, is provided at the receiver input. Frequencies are so low, that the cable is at all frequencies shorter than one eighth of a wavelength. The antenna output impedance forms, with the cable output impedance, a band-pass filter whose nominal impedance is real and greater than the cable characteristic impedance. Its pass-band covers the whole signal frequency range. The antenna output impedance is nearly real, nearly independent from frequency and greater than the cable characteristic impedance. The antenna real impedance is so high, that the band-pass filter upper cut-off frequency is only a little above the highest signal frequency.