Abstract
Described is a ew 10kW MOS-FET transmitter composed of the new single unit type modulator and the 10kW power amplifier. The new modulator was designed on the bases of the high voltage/low current mode of operation which consists of : high load impedance ; optimum design to maximize drain efficiency ; and suitable thermal design to protect MOS-FET's and low-pass filters against local temperature increase. The MOS-FET's and other components meet the specifications defined by the above design bases. The modulator unit is 230 × 530 × 700mm3 in size and 21kg. Forced air cooling at a flow rate of 10m/s was employed to keep the temperature increase on the MOS-FET case surfaces at 9°C, and on the low-pass filter coil surfaces at 31°C. Performance of the 10kW transmitter was : 82% or better power efficiency ; 2% distortion factor, and 52dB or better signal to noise ratio.
