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FU-728F
Specifications
FU-728F metal ceramic tube, forced air cooling, indirectly heated oxide cathode, plate dissipation
power 1.2 kW, mostly in Class-AB linear high frequency amplifiers, audio amplification, applies
specifically to 1.6 kW SSB final stage transmitter linear amplifiers.
Characteristic parameters
Filament voltage ………………………………………………...…….. 9 V
Filament current ………………………………………………… 8,5 – 9 A
Transconductance …………………………...…………… >= 14.3 mA/V
Amplification factor ……………………………………………….…… 4.2
Negative bias voltage ………………………………………..…… -78.5 V
Interelectrode capacitances (grounded cathode)
Input max. ……………………………………………………….…… 103 pF
Output max. ………………………………………………...…….…. 13.3 pF
Transfer max. …………………………………………………..……. 0.05 pF
Operating position ………………………………………….………. vertical
Cooling air speed …………………………………………....……. 3 m3/min.
Temperature at metal/ceramic seals …………………...….………. 250 oC
Height max. ………………………………………..…………..….. 132.5 mm
Diameter max. ……………………………………………….…….. 86.5 mm
Mass max. ………………………………………………..……..……… 950 g
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Maximum ratings
f = 110 MHz
Cathode warm up time …………………………………...…………... 3 min.
Peak surge filament current ……………………………...………….. 12.5 A
Below 110 MHz
Filament voltage error …………..…………………….……...…….... +/- 5%
Plate voltage DC ……………………………………….……....………. 3 kV
Grid 2 voltage max. …………………………………….……...……… 400 V
Plate dissipation ……………………………………………….....…. 1200 W
Grid 2 dissipation ………………………………………………..……. 12 W
Grid 1 dissipation ………………………………………………..……... 1 W
Typical operation
High Frequency Power Amplifier or AB1-Class modulator
Plate voltage ………………………………………………..………. 3000 V
Grid 2 voltage .…….………………………………….……………… 350 V
Grid 1 voltage ………………………………………….…….………… -79 V
Plate dissipation …………………………………………………..…. 1200 W
Grid 2 dissipation ………………………………………………………. 12 W
Grid 1 dissipation …………………………………………………..…... 0 W
Plate current ………………………………………..………………..…. 0.9 A
Peak Output Power (dual) …………………………………..……… 2.5 kW
Output Power (single) ………………………………………..……… 1.8 kW
1 kW FM Class C
Plate voltage ………………………………………………..………. 3000 V
Grid 2 voltage .…….………………………………….……………… 200 V
Grid 1 voltage ………………………………………….…….………… -55 V
Filament voltage …………………………..……………………...…….. 9 V
Cathode current …………………………………………………..…. 450 mA
Grid 2 current ………………………………………………………….. -2 mA
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Socket
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