Compare the
GS-35B With the 3CX1500A7/8877
(See photographs below)
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
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

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.


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.
GS-35B Planar Anode
This one has had the BIG BANG
8877 Conical Anode
I'm looking for a photo of the innards of the 8877 anode. It is nothing more than a copper tube.