GI7b/GI70b/GI7bT 
Microwave Triode 
The GI7b, GI70b and
GI7bT microwave triode operates as an oscillator or an amplifier in continuouswave or pulsed
mode with anode modulation in the centimetric and decimetric wavelength ranges. The
GI7"b" is available in two variants differing in the type of cooling: the GI7b with a
heat sink for forced air cooling and the GI70b with no heat sink for other systems of cooling.
The GI7b is physically identical to the GI6b and GS9b, although there are electrical
differences. The GI7bT comes with heat sink only, is more shock and vibrationproof,
and has a larger ceramic structure. It is designed to be used in Tanks. The "bT"
varies in a few parameters from the "b", and these variations are noted in the tables below.
As with most Russian power triodes, the heat sink on the GI7b & GI7bT is removable.
NOTE: Myriad tests have been conducted
regarding the use of this tube for PAs at 23cm. It is possible to derive a stable output of
of up to approximately 250W from a single tube GI7B cavity PA, and designs for such PAs can be
found on this web site. Even with outstanding cooling, higher powers result in severe
thermal drift problems. The most forgiving design is by OK1KIR, because it uses a 1/4 w.l.
anode cavity which is quite broadbanded compared with the 3/4 w.l. cavities normally used.
Even the extensive additional cooling measures used in the OK1KIR design do not
solve the thermal drift problems. Additionally, this design will not accept the GI7BT due to
physical limitations imposed by internal cavity dimensions. In short, the GI7's internal
dimensions are simply too big (too large in terms of electrical wave length) to allow this
tube to be used effectively at 23cm. The GI7 IS, however, well suited for use in single and
multipletube PAs from HF through 70cm, and designs for such PAs are also on this web site
(with more added as found!).

GENERAL  
Cathode: indirectly heated, dispenser, oxidecoated.  
Envelope: metalceramic.  
Cooling: 24 m^{3}/hr forced air (GI7bT; 27 m^{3}/hr). For 350W dissipation, 40 m^{3}/hr is required by all!  
Height, mm, at most:  with heat sink: 110.5 
without heat sink: 97  
Diameter, mm, at most:  with heat sink: 65 
without heat sink: 36.3+  
Mass, gm, at most:  with heat sink: 330 
without heat sink: 170 
A  anode; C  grid; KP  cathode and heater; P  heater 
Note the physical difference of the GI7bT compared to the GI7b is in the "ceramic" portion of the body; 47mm diameter instead of a bit less than 36mm! 
OPERATING ENVIRONMENTAL CONDITIONS  
Vibration loads:  
frequency, Hz  5600 
acceleration, m/s²  59 
Multiple loads with acceleration, m/s²  342 
Single impacts with acceleration, m/s²  1,465 
Linear loads with acceleration, m/s²  490 
Ambient Conditions:  
Temperature, °C  60 to +100 
Relative humidity at up to +40 °C, %  9598 
NOMINAL ELECTRICAL PARAMETERS  
Heater voltage, V  12.6 
Heater current, A  1.925 
Mutual conductance (V_{a} = 1.2 kV, I_{a} = 150 mA, change in V_{g} = 1V), mA/V:  >23 
Operating point (negative V_{g} with V_{a} = 1.3KV, I_{a} = 150mA), V:  10 
input capacitance, pF:  11.1 
output capacitance, pF:  4.6 
transfer capacitance, pF:  0.075 
Warm up time (V_{a} = 400V), at most  90 
Output, CW operation (V_{a} =1.05KV, I_{a} =300mA, wavelength 18.5 cm), W (GI7b / GI7bT):  >30 / >40 
Output in pulsed operation (at peak V_{a} = 9KV,
I_{a} = 7.5A, wavelength 10 cm, 1/pulse duty factor 1,400150, pulse duration 310 ÷s), KW (GI7b / GI7bT): 
>11 / >12 
Designed Tube Life (hours)  >650 
ELECTRICAL PARAMETER LIMITS  
Heater voltage, V  1213.2 
Heater current, A  1.82.05 
Mutual conductance (V_{a} = 1.2 kV, I_{a} = 150 mA, change in V_{g} = 1V), mA/V:  2026 
Operating point (negative V_{g} with V_{a} = 1.3KV, I_{a} = 150mA), V  7.512.5 
input capacitance, pF  1012.2 
output capacitance, pF (GI7b / GI7bT):  45.2 / 4.25.0 
transfer capacitance, pF:  0.0550.095 
Maximum CW Anode voltage (V_{a}), KV:  2.5 
Maximum Instantaneous value Anode voltage (V_{a}), KV:  5 
Instantaneous value Grid voltage (V_{g}), V  400 to +80 
Maximum CW Cathode current (I_{c}), r.m.s./key down, A  0.6 / 0.4 
Anode Dissipation, W:  350 
Grid Dissipation, W:  7 
Temperature at anode lead, °C  200 
Temperature at radiator, °C  160 
Temperature at cathode leads, °C  100 
Temperature at grid leads, °C  200 
Temperature at external ceramic parts, °C  250 
Minimum wavelength in CW operation, cm  10 
Minimum wavelength in pulsed operation, cm  9 
Air


Averaged Anode
Characteristic Curves: U_{f} = 12.6V 
Averaged AnodeGrid Characteristic Curves: U_{f} = 12.6V 
ContinuousWave Generation: L = 18.5cm 
Averaged Anode
Characteristic Curves: U_{f} = 12.6V; _____ anode; _ _ _ gridanode; 