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Compare
the
GS-35B
With the 3CX1500A7/8877
(See photographs below)
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This
is a basic comparison of the GS-35B and the 3CX1500A7/8877. This information
is to be used for making up your own mind about which tube is for you .
I don't make any claims about the accuracy or source of any of this data. |
Specification
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GS-35B
medium mu
|
|
Length |
6.9
inches (177 mm) |
3.51 inches (89.15 mm) |
Diameter |
4
inches (100 mm) |
3.38
inches (85.85 mm) |
Weight |
6.17
lbs (2.8 kg) Anode cooler alone is 3 lb 7 oz (more than two complete 8877s) |
1
lb 9 oz (708 gm) |
Operating
Position |
Any |
Any |
Base |
Concentric
Rings (use simple clamps) |
Special
7 pin base |
Internal Construction |
Planar |
Conical |
Heater
Voltage/Current (Watts) |
12.6
Volts / 3 Amps (37.8 Watts) |
5
Volts / 10 Amps (50 Watts) |
Warmup
Time |
Greater
than 90 Seconds |
Greater
than 90 Seconds |
Maximum
Frequency Rating |
1000
MHz |
250
MHz |
Gain** |
13
dB (900 MHz) |
15.1
dB (< 30 MHz)
14.3 dB (220 MHz) |
Maximum
Output Power |
3000+
Watts |
2075
Watts |
Cin
(grounded grid) |
18-24
pf |
42
pf |
Cout
(grounded grid) |
3.8-5.0
pf |
10
pf |
Cpk
(Transfer c-a) |
<0.12
pf |
0.1pf |
Cathode |
Indirectly
heated oxide coated |
Indirectly
heated oxide coated |
Plate
Voltage Absolute Maximum |
6000
V (pulse) 4000 V SSB/CW |
4000
V |
Plate
Current Absolute Maximum |
1.4
Amps |
1.0
Amp |
Plate
Dissipation |
1500
Watts (>2500 Watts) |
1500
Watts |
Grid
Dissipation |
26
Watts |
25
Watts |
Forced
Air Cooling Minimum Volume |
88.3
cfm (2500 lpm)* (150 cmh) >10,000' |
38
cfm (1076 lpm) (65 cmh) sea level |
Approximate
Least Cost (Jan, 2006) |
US
$110.00 each |
More
than US $900.00 each |
|
*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
88.3 cubic feet per minute. |
** Let's work this gain and max output thing backwards:
Plate dissipation |
Maximum power input
based on 60% efficiency |
Maximum power
Output |
Tube Gain |
Required Drive |
1000 Watts |
2500 Watts |
1500 Watts |
15.1 dB |
46 Watts |
1000 Watts |
2500 Watts |
1500 Watts |
13 dB |
75 Watts |
1500 Watts |
3750 Watts |
2250 Watts |
15.1 dB |
70 Watts |
1383 Watts |
3458 Watts |
2075 Watts |
15.1 dB |
64 Watts |
1500 Watts |
3750 Watts |
2250 Watts |
13 dB |
113 Watts |
2500 Watts |
6250 Watts |
3750 Watts |
13 dB |
188 Watts |
1333 Watts |
3333 Watts |
2000 Watts |
13 dB |
100 Watts |
2000 Watts |
5000 Watts |
3000 Watts |
13 dB |
150 Watts |
2667 Watts |
6667 Watts |
4000 Watts |
13 dB |
200 Watts |
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What does all this mean?
It means that if you run an 8877 in class AB Grounded Grid with a maximum of 60% efficiency, and with the maximum rated power output of 2075 Watts, the dissipation of the tube will be 1383 Watts and the required drive would be 64 Watts. It means if you drive the 8877 with 70 Watts to get to the 1500 Watts maximum plate dissipation, you've exceeded the rated maximum power output by 175 Watts.
It means that if you use a 100 Watt transceiver, you can drive the GS-35B with 75 Watts, get 1500 Watts output and have headroom to spare. 100 Watts drive should yield 2000 Watts output with a plate dissipation of only 1333 Watts.
Using these examples you should be able to figure out the rest of the numbers in the chart above. |
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GS-35B
Planar Domed Grid
This one has been through the BIG BANG |
8877
Conical Grid
Rich, AG6K, shows gold sputtering. Thanks to him and his wife Susan who took the photo. |
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GS-35B Planar Anode
This one has had the BIG BANG |
8877 Conical Anode |
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I'm looking for a photo of the innards of the 8877 anode. It is nothing more than a copper tube. |
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