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GS-35B
Triode *Specifications
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The
GS-35B is a medium mu triode that yields about 13 db gain in amateur
service. These same specifications can be applied to the GS-7B (not to be confused with the GI-7) which
appears to be an old commercially produced version of the GS-35B. Although
the GS-31B has the same base as this tube, it has a much smaller anode
cooler and is rated for much less power. Amateur amplifiers have been
built using this tube for every band from 160 meters through 23 cm.
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*
PLEASE NOTE
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so called "Specification Sheet" for the GS-35B
was provided for the tubes as they were produced in
the Union factory for the Russian military and select
civil aviation customers. These tubes were produced
primarily for use in UHF RADAR applications (according
to my source in Russia). The factory was manufacturing
the tube in such a manner as to guarantee their performance
under the specified conditions. The maximum plate dissipation
of 1,500 watts was a CONSERVATIVE rating for this tube
in service above 800 MHz. Use of this tube in the spectrum
occupied by the amateur bands 160 meters through 70
centimeters was never specified nor measured. Imperical
knowledge of the use of this tube by many amateurs indicates
that for use in those amateur bands, with plenty of
air flow, you can expect up to 2,500 watts plate dissipation (plenty of air flow means more than
the specified 83.3 cfm; it isn't too much air until
you blow the tube out of the socket). You can also exceed
the rated anode voltage specification of 3,000 volts
to as much as 4,000 volts. The majority of users are
operating their amps with anode voltages between 3,000
and 4,000 Volts. There have been some uses up to 5,000
Volts (use extreme caution at these high voltages because the BIG BANG is VERY likely above 4000 Volts)).
Caution should also be exercised when operating the
tube with filament voltages that may go below the nominal
12.6 volts. If your line voltage drops enough to cause
your filament voltage to go below this level, you should
adjust the filament voltage so that it will stay at
or slightly above 12.6 volts under all conditions. Low filament
voltage not only contributes to rapid tube failure,
it will also cause your tube to have low output. Some
users claim to run the filament voltage as high as 14 volts.
Unlike directly heated cathode tubes, significant loss
of the oxide coating on the indirectly heated cathode
can occur with low filament voltages. High filament voltage can significantly shorten the life of the tube. You may shorten
the life of the tube slightly by raising the filament
voltage but not nearly as much as you will shorten it
running low voltage. Always provide for a method to
test and adjust your filament voltage. |
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WARNING!
DANGER! HIGH VOLTAGE!
This tube uses extremely dangerous high voltages.
These voltages will not just shock you, they will kill
you.
Use extreme caution while building, working on and testing.
Always THINK SAFETY! Only YOU can prevent
accidents.
Tony, W4ZT
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| Physical
Characteristics |
| Envelope
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metal-ceramic
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| Cooling
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forced
air |
| Minimum
required
Air flow |
2500
l/min
(83.3 cfm)** |
| Diameter
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100.2
mm max |
| Length
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min
173 max 177mm (6.9") |
| Anode
Diameter |
min
99.7 max 100.2 mm (4") |
| Grid
diameter |
min
59.5 max 60.3 mm |
| Cathode
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indirectly
heated, oxide coated |
| Cathode
Diameter |
min
40 max 40.5 mm |
| Heater
Diameter |
min
25.6 max 26.2 mm |
| Weight
including copper heatsink |
2.8Kg
(6.17 lbs) |
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| **Commonly
published data shows 1500 liters/min as 90 cfm but that conversion is WRONG.
The correct data is 2500 liters/min or 150 cubic meters per hour which is
83.3 cubic feet per minute. 90 cfm is still a good target number. |
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OK, Translate
this for me please...
- The anode
(A) diameter of 100.2 mm is close enough to 4 inches for government
work. It is 3-3/32 inches high.
- The grid
ring (C) is used for mounting the tube. It has a flanged ring
that's 60.3 mm in diameter which fits a 2-3/8 inch hole. The 65
mm diameter flange will rest on the edge of that hole as long
as you clamp it well. The flange measures about 0.29 inches thick.
This mounting is critical for removing heat from the grid and
the lower part of the tube as well as the critical grid to ground
electrical connection.
- The connection
for the filament and cathode (kn on the diagram) is 1-3/4 inches
in diameter.
- The other
filament connection (n) is 1-1/16 inches in diameter.
- The GS-35B
is heavy at just over 6 lbs including the copper heatsink.
- One thing
needs clarifying: The spec sheet says the life to be expected
from a GS-35B is 500 hours. This is a very conservative rating
provided by the Union plant for the Russian military. There are
a number of these tubes in service with a few thousands of hours
operating time with no indication of a decrease in emission or
filament failure. See the note above.
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| Electrical
Parameters (*conservative
military ratings for UHF RADAR service, see note above) |
| Heater voltage (Volts)
11.9-13.3
VAC / Typical 12.6 V |
12.6 |
| Heater current (Amps)
(Typical
12.6 V / 2.95 (+/- 0.3) A) |
2.65-3.25
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| Mutual conductance
(at anode = 2.5 kV, grid voltage change -1 V, anode current
0.4 A), mA/V |
25-40 |
| Penetration factor
(at anode voltage 2.5 kV, grid voltage change -200 V, anode
current 0.4 A), % |
0.8-1.2 |
| Operating point
(negative grid voltage at anode voltage 2.5 kV, anode current
0.4 A), V |
12-6 |
| Warm up time (seconds)
at LEAST |
>90 |
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Interelectrode
capacitance (pF):
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| Input C, (c-g) |
18-24 |
| Output C, (g-a) |
3.8-5.0 |
| Transfer
C, (c-a) |
<0.12 |
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Output power
(Watts) (*For operation near the
upper limit of the tube and very conservative. See note above)
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| at anode voltage
2.5 kV, anode current 0.7 A, wavelength 60 cm, at least
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800 |
| at anode voltage
2.2 kV, anode current 0.8 A, wavelength 30 cm, at least
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350 |
Output power over
500 h of service
(at anode voltage 2.5 kV, anode current 0.7 A, wavelength 60
cm), W, at least |
650 |
| Operational
Limits |
| Frequency |
1000 MHz |
| Heater voltage |
11.9-13.3* |
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Anode
voltage, kV:
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| DC |
3 |
| Instantaneous value
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6
(pulse) |
| Grid voltage |
-400 to +120 |
| Cathode current
(Amps) |
1.4*
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Dissipation
(Watts):
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| Anode |
1500* |
| Grid |
26 |
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Temperature
(°C):
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| Anode |
200 |
| Grid and cathode leads
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120 |
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| Environmental
Limits |
| Vibration frequency range,
Hz |
50-200 |
| Acceleration, m/s²
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59 |
| Multiple impacts with
acceleration, m/s² |
343 |
| Linear loads with acceleration,
m/s² |
88 |
| Lowest ambient temperature,
°C |
-60 |
| Relative humidity at up
to +40 °C, % |
98 |
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Averaged Anode and Grid-Anode
Characteristic Curves:
Uf = 12.6V
_____ anode;
_ _ _ grid-anode |
Characteristic Curves Showing Output
Power versus Anode Current:
Uf = 12.6V; L = 30cm |
Characteristic Curves Showing Output
Power versus Anode Current:
Uf = 12.6V; L = 60cm |
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Click
here for Data Sheet in PDF format (176k)
* Remember, this data is the very conservative
military data for use at UHF and not anything like the commercial specifications
you expect to see from a manufacturer of tubes you will find in commercial
service. Please see the note above for a better idea of what you can do
with this tube.
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These
are the dimensions for the tube base and hole cutout that I use
They have been converted to inches
(click
on the picture to get a larger printable image in a new window)
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