GU81M
PENTODE
The GU81M pentode is used in selfexcited oscillation and power amplification circuits of RF equipment.
GENERAL
Cathode: directly heated, carbonized thoriated tungsten.
Envelope: glass, with base.
Height: at most 260 mm.
Diameter: at most 202 mm.
Mass: at most 1 kg.
1, 2  cathode; 3  grid 1; 4  grid 2; 5  cathode centre tap; 6, C3  grid 3; A  anode
OPERATING ENVIRONMENTAL CONDITIONS  
Ambient temperature, °C  10 to +55 
Relative humidity at up to +25 °C, %  98 
BASIC DATA Electrical Parameters 

Filament voltage V  12.6 
Filament current, A, at most  11 
Mutual conductance (at anode voltage 2 kV, grid 2 voltage 600 V, anode current 200 mA), mA/V  4.56.5 
Gain coefficient (grid 1 grid 2) (at anode voltage 2 kV, grid 2 voltages 600 and 500 V, anode current 200 mA)  2.54 
Bias voltage (at anode voltage 2 kV, grid 2 voltage 600 V), V  116160 
Interelectrode capacitance, pF:  
input  2532 
output  2126 
grid 1anode, at most  0.1 
grid 1grid 3  14 
Output power (at anode voltage 2 kV, grid 2 voltage 600 V, bias voltage 200 V, grid 1 drive voltage amplitude 300 V, anode current, at least 450 mA, grid 1 current at most 20 mA, grid 2 current, at most 220 mA), W, at least  700 
Limit Operating Values  
Filament voltage, V  11.613.4 
Anode voltage, V:  
at frequencies not above 6 MHz  3 
at frequencies not above 24 MHz  2.5 
at frequencies not above 50 MHz  1.5 
Grid 2 voltage, V  600 
Anode current (average value), A  0.6 
Grid 1 current (average value), A  0.02 
Grid 2 current (average value), A  0.2 
Dissipation, W:  
anode  450 
anode (momentary dissipation)  600 
grid 2  120 
grid 1  10 
Envelope temperature, °C  350 
Averaged Anode Characteristic Curves:
U_{f} = 12.6V; U_{g2} = 0.5kV;
— • — (P_{a max})
Averaged Grid 2Anode Characteristic Curves:
U_{f} = 12.6V; U_{g2} = 0.5kV
Averaged Characteristic Curves:
U_{f} = 12.6V; U_{g2} = 0.6kV
Averaged GridAnode Characteristic Curves:
U_{f} = 12.6V; U_{g2} = 0.5kV
Averaged GridAnode Characteristic Curves:
U_{f} = 12.6V; U_{g2} = 0.6kV
Averaged Characteristic Curves:
U_{f} = 12.6V; U_{a} = 2.5kV;
_____ anodegrid;
_ _ _ grid 2