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ID = 21995
Tube type:  Transmitting Tetrode, air cooled   beam power   VHF 
Identical to 4X500A = QBL4/800 = PL-4X500A = FU-500F
Similar Tubes
Other base and data slightly different:

Base SPECIAL TUBEBASE in general Top contact with a cap.
Was used by Transmittertube (Radio)
Filament Vf 5 Volts / If 13.5 Ampere / Direct

Integral radiator, special 4-pin base with metal ring connected to G2. Glass or ceramic spacer depending upon manufacturers.

  • 500 W max plate dissipation with forced air cooling
  • 120 MHz max frequency full ratings, up to 250 MHz at reduced ratings.
Weight 765 g / 26.98 oz
Information source - - Manufacturers Literature   
Tube Lore (I)
4X500A: Private collection
Emilio Ciardiello

4X500A: Valvo,Senderöhren, 1983
Anonymous 15 Collector

4X500A: Valvo,Senderöhren, 1983
Anonymous 15 Collector

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