LONG LIFE 100 W TRIODE FOR ATC AND TELEMETRY TRANSPONDERS

Abstract

Further development of the Siemens planar triode type RH7C-c used in the Mariner IV S-Band transponder resulted in the conduction-cooled type YD 1380 and air-cooled version YD 1381. These metal ceramic tubes produce a CW output power of 100 W in L/S-Band with a high efficiency around 40%. Small signal gain is 17 dB, and a large signal gain of 14 dB with a 20 MHz bandwidth is achieved. Life of selected sample tubes exceeds 25,000 hours, three times higher than the figure specified for the Mariner IV tube. These tubes incorporate an osmiated metal. dispenser cathode to achieve long life with stable performance. This type of cathode is exceptionally resistant to bombardment by electrons turned back to the cathode as a result of transit-time effects in the cathode-grid space. In transponder applications this allows long intervals between maintenance to be specified for the output stages. Because of the rugged tube design and low weight of the complete amplifier, the YD 1380/81 is also suited for spacecraft applications. An air-cooled, 100 W CW amplifier for 1.6 GHz has a diameter of only 74 mm and length of 175 mm. The laboratory prototype including triode YD 1381 weighs 900 gms, but this weight can be halved if necessary. Fig. 1 shows the tubes YD 1380 and YD 1381. The main applications for these new tubes are in ATC systems, telemetry, L-band communication UHF and L-band TV (ETV) and SSB microwave link equipment.