Abstract: A variable duty cycle ultrasonic inverter is used to invert unregulated direct current into a high frequency variable pulse width modulated signal that is applied to a low frequency inverter by means of a high frequency transformer. The output of the low frequency is applied to an output filter where a feedback signal is coupled back to the variable duty cycle ultrasonic converter which is controlled by a comparison of the feedback signal and a sinusoidal reference signal. The sinusoidal reference signal is also used to control the low frequency inverter.

Abstract: A high frequency communication system has at least two stations with each station having a discrete address, a transmitter, a receiver and a means for selecting the preferred frequency for transmitting at least a preselected format between the station includes a means for sequentially tuning the receiver through a group of channels with each channel having a preselected frequency and bandwidth, a means for measuring the link quality of each channel that is received according to the discrete address of the station transmitting the message. After the link quality is measured it is stored in a link quality matrix according to the channel and address of the station transmitting the message, so that when transmission is initiated by the station receiving the message it may select the channel with the best link quality and initiate transmission on that channel if it is available.