The SP22 is a screened battery straight pentode for two Volt LT operation. Use could be as mixer, HF amplifier or detector. The only difference between the SP22 and SP210 are small differences in inter electrode capacitances.
The reverse of the envelope is plain zinc paint.
The classic envelope is 32 mm in diameter, and excluding the MO base pins is 87 mm tall.
References: Datasheet, 1040 & 1043. Type SP22 was first introduced in 1938.
Absolute Maximum Operating Conditions¶
Updated March 18, 2014. shape:classic construction:pinch type:pentode age:1930.1940 base:mo heater:2.0v pins:8 pin:1.f pin:2.- pin:3.a pin:4.g2 pin:5.g3 pin:6.m pin:7.- pin:8.f pin:tc.g1