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DC9DZ: Project Broadcast 4K – Power Amplifier (PA) using two GU78b

Data of DRESSLER Broadcast-4K RF AM Linear Amplifier

Frequency band complete 49 m band 5500 kHz to 7300 kHz
Power supply 2 power supply transformers (230 V primary) 7000 VA & 1.5 VA
Plate voltage 3150 V at full output power
Screen voltage 330 V stabilized
Grid voltage - 70 V +/- 10 V regulated
Filament 27 V / 7.5 A
Input SWR < 1.1 : 1
Gain 21 dB
Amplification Input power Output power  
30 W   4000 W  
There is absolute no time limit for a carrier output power of 4000 W
Harmonic Output 50 dB below rated output
IMD 36 dB or better
Tube Two Svetlana GU-78b
Input network 50 Ohm, 200 W HF Resistor,
5 pol. Chebychev Low Pass Filter
Output network Inductor: 3.5 uH, Caps: 250 pF var. / 1000 pF var.
Computer control Plate current (every 5 msec), SWR, all switching functions,
no relais switching under power conditions, soft start inrush, 180 sec delay time for full power, 2 speed turbine blower

Well regulated screen and grid supply for +ve and -ve currents as well as current limiting to protect the tube and minimize the IMD. It is impossible to override the screen and grid dissipation at any working conditions.
Metering Output, SWR, Plate current, Plate voltage,
Screen & Grid current / voltage
Housing High quality black eloxial aluminia
Dimension 548w x 159.5h x 512d mm³
Weight 58 kg
Supply Voltage 230 V / 30 A CEE
Price 8180 €
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