UHF transmitting triode. Double-helical thoriated tungsten center tapped filament for low inductance; tantalum anode. 40W plate power dissipation. Can be operated full ratings at 500MHz, up to 650MHz at reduced ratings.
Also made in Italy by Fivre during WWII. Two Fivre 1628s were used in the radar transmitter installed on the Littorio battleship.
