H. F. ACTIVE ANTENNA PERFORMANCE REQUIREMENTS AND REALIZATION.

An active antenna is defined as a combination of a small antenna element and a matching amplifier. As such, an active antenna, a relatively small receiving device, may replace large structures. Communication on h. f. is already difficult and it is imperative that the active antenna does not degrade the reception performance of receiving system. Rather than analyzing various circuit configurations, performance requirements for a successful active antenna are derived. An active antenna cannot be equaled in performance to a matched antenna because it introduces intermodulation products and noise. However, the degradation in performance can be made negligible if the active antenna is tailored to the operating conditions, taking into account the level of interfering frequencies and atmospheric, galactic and man-made noise. The article deals with the required performance specification. Severity of this specification limits execution to three basic forms.