Encyclopedia of radio electronics and electrical engineering / Civil radio communications

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The bandwidth of the proposed reversing amplifier is 6-7 octaves. The sensitivity of a transceiver with such an amplifier can reach 0,1 μV. From similar devices published earlier in [1, 2]. this option is characterized by a high level of undistorted output voltage and increased resistance to self-excitation. It can "rock" the final stage with an output power of 5 ... 10 W (QRP). The undistorted output voltage at a load of 50 ohms can reach 4 V. Other characteristics of the amplifier are indicated in the table.

The amplifier circuit is shown in the figure.

To switch the signal flow direction, power is supplied to one or another arm of the amplifier. For example, to pass a signal from XW1 to XW2, you need to apply power to connector X1. Nothing is connected to X2 (it can be "grounded").

Diodes VD1. VD2, VD4, VD5 are used to eliminate the self-excitation of the amplifier. Diodes VD3, VD6 and transistors VT2, VT4 allow you to achieve an undistorted voltage at the output of 4 V.

RF transformers T1 and T2 are wound on K10 * 6x4 rings made of ferrite grade NN with a magnetic permeability of 600 ... 2000. The winding is carried out by two pieces of PELSHO wire twisted together with a diameter of 0.25 to 0,33 mm. The twist step is as follows: 3-4 twists per 1 cm of length. The number of turns is 6-8.

Transistors VT1 and VT3 are mounted on heat sinks.

Setting up the amplifier basically boils down to adjusting the current consumption of its shoulders by selecting resistors R2 and R8. Non-inductive resistors with a resistance of 1 ... 2 Ohms are connected to the connectors XW47 and XW51. By applying power to connector X1. set the current consumption within 40 ... 45 mA by selecting the resistor R2. At the same time, X2 is not connected anywhere (it can be "grounded"). Then, by selecting the resistor R8, the current consumption of the other arm is set (by supplying power to X2 and disconnecting from X1).

If possible, equal current values ​​should be set for each of the arms of the amplifier. The value of 45 mA is taken from the consideration that the transistor VT1 (VT3) does not overheat even during prolonged operation.

If you use KT1A as amplifying transistors (VT3 and VT911) with appropriate heat sinks, you can increase the current consumption of each arm to 100 mA. This will slightly increase the maximum RF voltage at the output.

Literature

1. Artemenko V. A simple reversible IF amplifier. - KB magazine. 1998. No. 3. p. 31-34.
2. Artemenko V. A. Universal high-frequency reversing amplifier. - Radioamator. 1998. No. 8. from 20.21

Author: V.Artemenko (UT5UDJ)

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