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1.5KW GU-43B HF Linear by PA0FRI (Click on callsign for e-mail)
1.8 - 30 MHz, Input 50 ohm SWR <1.2:1

Schematic diagram as of June 2003 - PA without QSK

Pictures of PA circuitry under development. An excellent example of the term "bread boarding"!!
Click on pictures to enlarge.

GU-43B Socket

This experimental design is capable of 1.5kW output throughout the range 1.8 to 30MHz, 5W drive delivering 300-400W. The input is "swamped" by the 50 Ohm grid resistor eliminating the need to use tuned circuits to match the input circuit on the amateur bands. The simple screen supply incorporates protection circuitry comprised of a small 230V/15W household lamp as a constant current device. If the HV fails or the amplifier is not correctly tuned or is overloaded, the screen grid dissipation is limited to a safe value. If the pi-network output circuit is determined empirically for lowest screen current and maximum output, the screen supply is quite adequate and stabile.

In practice the GU-43B and equivalent Polish Q-1P/41 and Q-1P/42 are very rugged; they withstood temporary overload during my tests: screen grid 300mA, anode current 2A and 100W drive without 6dB attenuator. The GU-43B is extremely stabile in this design; no sign of oscillation even without in- and output loading.

Lowest screen current occurs with anode voltage 3kV < Ua < 3.3kV. With normal speech the screen current should flicker about zero mA (+/- 5mA). With a carrier ("key down") the screen current is about 20mA positive.

Q-1P/41 is a silver plated GU-43B; Q-1P/42 is a silver plated and ceramic GU-43B. Both types have a better amplification factor than the Russian GU-43B. They need 1.0 to 1.5V more negative bias (e.g., extra 1-2 diodes in series) and deliver 100-200W more output power.

If you wish to incorporate QSK function in this PA, modify the circuit above per the schematic below:

Feedback: Paul S. Goble, III, ND2X
Copyright © 2003 by ND2X and PA0FRI

Глас народа 23.07.2009 01:06 zdar......  --  om5hi
23.07.2009 00:50 ahoj 73!!!...  --  om5hi
26.01.2006 15:11 Да, все хорошо. Только желательно 500В подавать не все время,а в ...  --  YL3RW
22.01.2006 14:20 транзистор из схемы - ВU208А, после включения просто пробился... ...  --  UA9XTL
16.01.2006 19:31 Возможно вы применили транзистор с малым напряжением насыщения Ub...  --  YL3RW
08.01.2006 19:22 собрал стабилизатор питания экранной сетки, лампочка перегорает.....  --  UA9XTL
30.03.2005 13:17 Минус источника питания экранной сетки ГУ43Б должен подаваться на...  --  Vlad YL3RW

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