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Abstract

A frequency-modulated ultrashort-wave signal is received, but due to wave-reflection phenomena from physical bodies reflecting towards the receiving antenna is amplitude modulated, this amplitude modulation being dependent upon frequency. Derived from the frequency-modulated signal is a frequency-deviation signal indicating its instantaneous frequency deviation, and also an amplitude-indicating signal indicating its instantaneous amplitude. These can be fed to the x- and y-inputs of an oscilloscope for display of an amplitude versus frequency curve used to generate a quantitative characterization of reception quality, the oscilloscope screen being provided with a horizontal reference axis. In order that the horizontal reference axis implied by such curve stay in register with that on the screen, even during rotation of the receiving antenna, the amplitude-indicating signal is normalized with respect to the reflection-free amplitude value which the frequency-modulated signal would have in the absence of these wave-reflection phenomena. This is accomplished by applying the amplitude-indicating signal to a clocked amplitude regulator, which is clocked only when the frequency-deviation signal indicates substantially zero frequency deviation of the received frequency-modulated signal.

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First Claim