Abstract: A radio transmitter system includes: a transmitter for deriving a carrier frequency modulated by an input; an electrically short antenna system, and a matching network between the transmitter and antenna system. The matching network includes: a primary circuit responsive to the transmitter, a secondary circuit including the antenna system, and magnetic or capacitive coupling between the primary and secondary circuits. The magnetic coupling is an air core transformer having first and second windings respectively included in the primary and secondary circuits. The matching network has a voltage versus frequency response including at least two horns spaced from each other such that the matching network has a pass band approximately equal to the modulation bandwidth.

Abstract: A radio transmitter system includes: a transmitter for deriving a carrier frequency modulated by an input; an electrically short antenna system, and a matching network between the transmitter and antenna system. The matching network includes: a primary circuit responsive to the transmitter, a secondary circuit including the antenna system, and magnetic or capacitive coupling between the primary and secondary circuits. The magnetic coupling is an air core transformer having first and second windings respectively included in the primary and secondary circuits. The matching network has a voltage versus frequency response including at least two horns spaced from each other such that the matching network has a pass band approximately equal to the modulation bandwidth.

Abstract: A radio transmitter system responsive to a binary signal drives a narrow bandwidth VLF or LF antenna. A generator derives a first variable frequency wave frequency coded based on bit values of a binary signal. An arbitrary impulse response signal processor responsive to the first wave derives a first output signal having real and imaginary components representing the shape of a modulating wave having a variable amplitude envelope and the frequency of the coded values. A transmitter responsive to the processor output signal and a VLF or LF carrier supplies the antenna with another output signal including a modulation wave having a shape that is a substantial replica of the modulating wave shape. The processor causes the signal emitted by the antenna system to include modulation having a shape that is substantially the shape of the first wave.

Abstract: A radio transmitter system responsive to a binary signal drives a narrow bandwidth VLF or LF antenna. A generator derives a first variable frequency wave frequency coded based on bit values of a binary signal. An arbitrary impulse response signal processor responsive to the first wave derives a first output signal having real and imaginary components representing the shape of a modulating wave having a variable amplitude envelope and the frequency of the coded values. A transmitter responsive to the processor output signal and a VLF or LF carrier supplies the antenna with another output signal including a modulation wave having a shape that is a substantial replica of the modulating wave shape. The processor causes the signal emitted by the antenna system to include modulation having a shape that is substantially the shape of the first wave.