GI-7B.pdf

GI-7b/GI-70b/GI-7bT

Microwave Triode

The GI-7b, GI-70b and GI-7bT microwave triode operates as an oscillator or an amplifier in

continuous-wave or pulsed mode with anode modulation in the centimetric and decimetric

wavelength ranges. The GI-7"b" is available in two variants differing in the type of cooling:

the GI-7b with a heat sink for forced air cooling and the GI-70b with no heat sink for other

systems of cooling. The GI-7b is physically identical to the GI-6b and GS-9b, although there

are electrical differences. The GI-7bT comes with heat sink only, is more shock- and

vibration-proof, 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 GI-7b & GI-7bT 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 250 W 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 multiple-tube 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, oxide-coated.

Envelope: metal-ceramic.

Cooling: 24 m 3 /hr forced air (GI-7bT; 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

Note the physical difference of the GI-7bT

compared to the GI-7b is in the "ceramic" portion of

the body; 47mm diameter instead of a bit less than

36mm!

A - anode; C - grid; KP - cathode and heater;

P - heater

OPERATING ENVIRONMENTAL CONDITIONS

Vibration loads:

frequency, Hz

5-600

acceleration, m/s²

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, %

95-98

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:

input capacitance, pF:

11.1

output capacitance, pF:

4.6

transfer capacitance, pF:

0.075

Warm up time (V a = 400V), at most

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 1,400-150, pulse duration 3-10 ÷s), KW (GI7b / GI7bT ):

> 11 / > 12

Designed Tube Life (hours)

> 650

ELECTRICAL PARAMETER LIMITS

Heater voltage, V 12-13.2

Heater current, A 1.8-2.05

Mutual conductance (V a = 1.2 kV, I a = 150 mA, change in V g = 1V), mA/V: 20-26

Operating point (negative V g with V a = 1.3KV, I a = 150mA), V 7.5-12.5

input capacitance, pF

10-12.2

output capacitance, pF (GI7b / GI7bT ):

4-5.2 / 4.2-5.0

transfer capacitance, pF:

0.055-0.095

Maximum CW Anode voltage (V a ), KV:

2.5

Maximum Instantaneous value Anode voltage (V a ), KV:

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:

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

Minimum wavelength in pulsed operation, cm

Air

m 3 /hr

P a , W

Averaged Anode Characteristic Curves:

U f = 12.6V

Averaged Anode-Grid Characteristic Curves:

U f = 12.6V

ContinuousWave Generation:

L = 18.5cm

Averaged Anode Characteristic Curves:

U f = 12.6V;

_____ anode;

_ _ _ grid-anode;

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