INVESTIGATION OF ATMOSPHERICS IN THE FREQUENCY RANGE OF 0 - 100 CYCLES PER SECOND BY MEANS OF MEASUREMENTS WITH NARROW BAND AMPLIFIERS

摘要

A survey is given on the possibilities for realizing narrow band amplifiers for extremely low frequencies. It was found that feedback amplifiers with twin-T RC networks in the feed¬back loop are most suitable for lowest frequencies. Such a feedback amplifier filter is theoretically analyzed as to whether it can be used as frequency analyzer. Special methods for measuring and calibrating the Q and the spectral ampli¬tudes are shown. These methods are based on the application of the frequency spectrum of short square pulses.