[en] Over the past 18 months the EBT-S 28-GHz 200 kW cw mixed mode ECH system efficiency has increased from 70 to 80% by the substitution of 90⁰ smooth radius W/G bends for the earlier miter bends, by eliminating several mode absorbers necessary for miter bend operation, and by optimizing the microwave coupling through the quasi-optical toroidal distribution manifold. Along with reduced system losses, these improvements have allowed the gyrotron sources to operate in a wider parameter range with high dc to rf conversion efficiency than previously attainable. Other components that have been developed besides radiused bends include T/sub i/O₂ mode absorbers, power splitters, bellows, and several types of high field mixed mode launchers. Details on these components will be presented as time allows