Abstract: A short monopole RF antenna tuned over a predetermined RF frequency band in response to binary control signals includes a conductive tubular radiating element extending generally at right angles to a ground plane on which the antenna is mounted. A conductive top load inductively coupled to the element extends approximately parallel to the ground plane so that stray capacitance subsists between the ground plane and top load. The antenna is tuned in response to the control signals to a frequency in the band by selectively short-circuiting different plural series-connected inductors in proximity with the top load. Plural leads extend through the interior of the tubular element between a source of the control signals and switches for selectively short circuiting the inductors. The inductors are electrical conductors in a tube-like structure. The leads extend through the interior of the tube-like structure. Electrical conductors in the tube-like structure are in a return path to the control signal source.

Abstract: So as to allow modification of the radiation diagram of a rotary curtain antenna, the doublets of a curtain are distributed in groups of one or several doublets and each group has its own feed line which connects it to a switching box situated in the mast of the antenna and which is constructed so as to bring to the box an impedance inversely proportional to the number of doublets fed by this line; this box allows all or part of the groups of doublets to be fed at will from a mast down line. Dynamic impedance matching cells disposed at the foot of the antenna provide a small standing wave ratio for connection with a transmitter.