GU74b 
Tetrode 
The GU74b tetrode is used in wideband nontunable amplifiers and
for singlesideband power amplification in stationary and mobile RF equipment. It is
useful at full ratings through 250MHz. The GU74b tetrode is generally considered to
be similar to the 4CX800A, although some users report that it acts more like a tube having
900 or 1000W anode dissipation.

GENERAL  
Cathode: indirectly heated, dispenser, oxidecoated.  
Envelope: metalceramic.  
Cooling: forced air.  
Height, mm, at most:  90 
Diameter, mm, at most:  71 
Mass, gm, at most:  550 
I  contact surfaces; 1  grid 1; 2, 4, 6  cathode; 3, 7  heater; 5, C2  grid 2; A  anode 
ENVIRONMENTAL OPERATING CONDITIONS  
Vibration loads: 

frequency, Hz  1200 
acceleration, m/s²  49 
Multiple impacts with acceleration, m/s²  392 
Ambient Conditions:  
Temperature, °C  10 to +55 
Relative humidity at up to +35 °C, %  98 
NOMINAL ELECTRICAL PARAMETERS  
Heater voltage, V  12.6 
Heater current, A  3.6 
Mutual conductance (V_{a} = 1KV, V_{g2} = 300V, I_{a} = 600mA, change in V_{g1} = 2.5V), mA/V:  32.5 
Anode current (I_{a}) with V_{a} = 2.5KV, V_{g2} = 300V, A:  >1.4 
Negative bias (V_{g1}) with V_{a} = 1KV, V_{g2} = 300V, I_{a} = 600mA, V:  1832 
Negative cutoff bias (V_{g1}) with V_{a} = 1KV, V_{g2} = 300V, I_{a} = 15mA, V:  90 
input capacitance, pF  51 
output capacitance, at most, pF  11 
transfer capacitance, pF  <0.09 
Warm up time, s:  <150 
AB_{1} Output power, V_{a} = 2KV, V_{g1} = 60V, V_{g2} = 300V, I_{g2} < 50mA, Freq. 0.11.0 MHz, W:  >550 
3rdorder energy relative to carrier, V_{a} = 2KV, V_{g2} = 300V, I_{g2} < 50mA, V_{g1} = 70V, dB:  28 
5thorder energy relative to carrier, V_{a} = 2KV, V_{g2} = 300V, I_{g2} < 50mA, V_{g1} = 70V, dB:  28 
Designed Tube Life (hours)  >1500 
ELECTRICAL PARAMETER LIMITS  
Heater voltage, V  11.913.3 
Heater current, A  3.33.9 
input capacitance, pF  4656 
output capacitance, pF  913 
Maximum CW Anode voltage (V_{a}), KV:  2 
Maximum Instantaneous value Anode voltage (V_{a}), KV:  4 
"Maximum" Control Grid voltage (V_{g1}), V  150 
Maximum Screen Grid voltage (V_{g2}), V  300 
CW cathode current (I_{c}), A:  0.75 
Peak cathode current (I_{c}), A:  2.5 
Anode Dissipation, W:  600 
Screen Grid (G2) Dissipation, W:  15 
Control Grid (G1) Dissipation, W:  2 
Frequency, MHz:  <250 











