VEBR power amplifier. Scheme, description

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VEBR power amplifier. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / RF power amplifiers

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Technical specifications

Output power - 8...15 W.
Current consumption in the "Receive" mode - 10 mA.
Current consumption in the "Transfer" mode - 3 A.

This power amplifier is designed and manufactured by the Voronezh Experimental Bureau of Radio Communications. The amplifier has two modifications - for operation in the 40 MHz (VEBR-UM-40 / 8-10) or 27 MHz (VEBR-UM-27-10) bands, designed to work in conjunction with the VEBR-NR radio station [1], but can be used with other radios. The variant for use in the 27 MHz band is described below.

The circuit diagram of the power amplifier is shown in the figure. Its distinguishing feature is the presence of an electronic "reception-transmission" switch. Switching to the transmission mode occurs when the power supply is on and the output signal from the radio station is applied to the input of the amplifier, i.e. when the radio is in transmit mode. When the power supply is off, the amplifier operates in "Bypass" mode and does not require disconnection of the amplifier cables.

In receive mode, the signal from the antenna is fed to the XS1 connector. After passing the output filter of the amplifier and the two-section P-filter, the signal enters the A1 connector. The weakening of the receiver signal - no more than 1,5 dB. In transmit mode, the signal from the radio is sent to connector A1. When the power is on (switch S1), part of the input signal through C2 goes to the base of the transistor VT2. The transistor opens, which leads to the opening of the key on the transistor VT1 and the lighting of the HL LED, indicating the "Transmission" mode. This also opens the transistor VT5, which serves to supply power to the amplifier and unlock the diodes VD2, VD5, which are electronic switches "Receive / Transmit". The input signal is fed to an amplifier made on a VT6 transistor of the KT930A type. To suppress harmonics at the output of the cascade, a four-section P-filter is used.

(click to enlarge)

It is not recommended to turn on the amplifier without a connected antenna and use it with antennas with an SWR worse than 2,5.

Diode VD3 is used to protect against reverse polarity of the supply voltage.

The winding data of the inductors for the 27 MHz band are shown in the table.

Position	Diameter mandrels, mm	Qty turns	Diameter wires, mm
L1	Throttle DPM-1, 2-6 μH
L2	7	7	0,56
L3	7	7	0,56
L4	Throttle DPM-1, 2-60 μH
L7		5	0,56
L8	Jumper
L9	7	8	0,56
L10	7	15	0,56
L11	7	5	0,56
L12	7	6	0,56
L13	Throttle DPM-1, 2-60 μH
L14	7	7	0,56
L15	6	9	0,56
L16	6	9	0,56
L17	6	9	0,56
L18	6	9	0,56

Literature:

1. Radio amateur No. 9 1999, p.39

Publication: N. Bolshakov, rf.atnn.ru

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