Amateur CF multi-band. Transceiver with quartz filter. Fig.4. UM printed circuit board drawing

The transceiver is designed for radio communications in the range of 160m (easily adjusted to 80m) and has the following parameters: Operating frequency range 1800-2000 (3500-3800) kHz; range Type of work - SSB.; Sensitivity at a signal-to-noise ratio of 10 dB, no worse than 1 µV; Selectivity in the mirror channel, no worse than 40 dB; Range of manual gain adjustment, not less than 60 dB; Peak output power transmitting path, at least 5 W (at a load of 50 Ohms); Suppression of side channels in transmit mode, no less than 40 dB.

The reversible path of this transceiver uses K174PS1 microcircuits, which are active balanced mixers with high conversion slope. Thanks to their use, the transceiver path has been significantly simplified - the number of winding units has been reduced, and it has become possible to do without an IF path and a separate microphone amplifier.

The load of the mixer during transmission is DPF С31L6С32L7С35. A pre-amplifier for the transmitter power is assembled on transistors VT3 and VT4. From the output of the main board, the radio frequency signal goes to the final power amplifier board. The final amplifier is assembled on field effect transistor KP901A. The output signal enters the antenna through a single-link low-pass filter. The transmitter output filter is designed to operate with a 50 Ohm active resistance load. To monitor the RF signal at the transceiver output, a simple detector is used (resistive divider R31R32, diode VD12 and microammeter PA1). The transceiver GPA is made on bipolar transistor according to the capacitive three-point circuit on transistor VT5. On transistor VT6 there is a buffer emitter follower of the GPA signal. The power supply provides a stabilized voltage of +12V and an unstabilized voltage of +34V (to power the final stage of the transmitter).
Transceiver parts.
The transceiver uses: Fixed resistors - type C1-4, C2-23, MLT; trimming resistors - SP3-38B. Non-electrolytic capacitors - K10-17, trimmers - type KT4-23. Electrolytic capacitors- K50-35. A KPI from a tube radio receiver was used as a tuning capacitor. The network transformer must have an overall power of at least 50 W and provide 2x13 V in the secondary winding AC voltage at a current of 1.5 A. The author used a transformer from the “Do it yourself transformer” amateur radio kit. Broadband transformers T2 and T3 are manufactured on K7x4x2 ferrite rings with a permeability of 600-1000 NN. The windings are wound in two wires and contain 2x20 turns of PEV 0.25. Chokes L4 and L8 are standard DM-0.1, L1 - D-0.6. The inductance of all chokes is 100 μH. DPF coils are made on SB9 armored cores and contain 30 turns of PEV 0.15 wire. The tap of the L3 coil is made from the 6th turn (counting from the grounded end); at L5 - from the middle. The low-pass filter inductance of the L2 transmitter is made on a ferrite binocular core from baluns used in domestic televisions. Winding is carried out with a single-core wire with a diameter of 0.4 mm in PVC insulation, the turns of the wire are passed through the internal holes of the core. The number of turns is 8. The L9 GPA coil is made on a frame made of heat-resistant plastic with a diameter of 12 mm with a tuning ferrite core and contains 40 turns of PEV 0.6 wire. Relay K1 - RES9 with a winding resistance of 500 Ohms (you can use any suitable relay with two groups of switching contacts. Relays K2 and K3 -RES49 with a winding resistance of 270 Ohms. You can also use a relay with high voltage triggering by connecting them in parallel. VM1 is a two-pin imported electret “tablet” microphone. PA1 is a pointer microammeter with a total deflection current of 50 - 100 µA.

The transceiver components are assembled on boards made of double-sided foil PCB, the top layer of metallization serves as a screen. Printed circuit board drawings are shown in Fig.2-5, arrangement of elements - on Fig.6-9, general layout in Fig. 10.

Fig.2. Main board. PP drawing

Fig.3. Drawing printed circuit board GPA

Fig.4. UM printed circuit board drawing

Fig.5. Rectifier printed circuit board drawing.

Fig.6. Main board - arrangement of elements.

Fig.7. GPA board. Arrangement of elements

Fig.9. Rectifier board. Arrangement of elements.

Fig. 10. Transceiver "Amator-160". Design.

The transceiver is assembled in a duralumin housing with dimensions 220x220x110, divided by a partition into two compartments - upper and lower. In the upper (larger) compartment there is a network transformer T1, a GPA board, a KPI, a rectifier board, a PA board, a K1 relay and a DA1 stabilizer. The transistor of the final amplifier VT1 and the stabilizer DA1 are screwed to the rear wall of the case, which acts as a radiator. The PA board is also mounted on the back wall on racks. The high-frequency detector is assembled using the volumetric mounting method and is located in close proximity to the antenna connector, also near the K1 relay connector. The main board is installed in the lower compartment of the case. The adjustment scale is a plexiglass disk with marked marks, attached directly to the KPI axis.
Setup.
Configuring the transceiver begins with the GPA unit. By adjusting the L9 coil and selecting the C46 capacitance, the operating tuning range of the GPA is set within the range of 2300-2500 kHz with some margin (10-20 kHz) at the edges of the range. The output level of the GPA should be in the range of 100-200 mV. After this, they begin to configure the main board. First of all, you need to make sure that the reference oscillator is working by connecting, for example, an oscilloscope probe to the emitter of transistor VT2. By applying a high-frequency generator signal to the transceiver input, the input DFTs are adjusted, after which, by adjusting C20 and C21, the maximum volume of the received signal is achieved. If you don’t have a generator, you can use signals from amateur radio stations for tuning.

Further configuration of the transceiver is carried out in transmission mode with the final stage turned off. Potentiometer R6 is used to balance mixer DA2, achieving maximum suppression of the reference oscillator signal. Balancing control is best done with an oscilloscope or a high-frequency millivoltmeter at the output of the EMF. If even with precise balancing of the mixer it is not possible to suppress the carrier within the required limits, it is necessary to reduce the voltage of the reference oscillator by increasing the value of resistor R7. By applying an audio frequency generator signal with an amplitude of 3-5 mV and a frequency of 500-1000 Hz to the microphone input of the transceiver, the DFT of the transmitter is adjusted. An RF millivoltmeter or oscilloscope is connected to the output of the main board (pins 11, 12) and by adjusting L6 and L7 the maximum readings are achieved in the operating frequency band. The preliminary stage of the transmitter must develop a voltage of at least 5V into a load of 500 Ohms. Before connecting the final stage of the transmitter, it is necessary to set the quiescent current of transistor VT1. Without supplying a high-frequency signal to the final stage, adjusting R2 ensures that the quiescent current of the transistor is in the range of 200-220 mA. The current is controlled with a milliammeter in the +34V circuit. The final stage settings - control the output power of the transmitter. Having connected all the components of the transmitter, connect a matched load to the antenna connector of the transceiver. A 5 mV-1000 Hz audio frequency generator signal is supplied to the microphone input. Using a millivoltmeter or oscilloscope, the voltage across the matched load is monitored in transmission mode. The voltage should be within 15-18 V. The current consumption of the final stage in the +34V circuit should be within 0.4A. Greater unevenness of the output power in the operating frequency range can be reduced by additionally adjusting the DFT of the transmitter and the low-pass filter of the final stage. By selecting R30, we ensure that the power indicator needle is in a sector of the scale that is convenient for observation.
The final stage of this transceiver is designed to work with antennas having a resistance of about 50 Ohms. When operating the transceiver with non-standardized antennas, it is necessary to use a matching device.

Alexey Temerev (UR5VUL), Svetlovodsk, Kirovograd region.

At one time, the author proposed several options for simple transceivers using K174PS1 mixer microcircuits. The proposed main transceiver board uses imported SA612 microcircuits. EMF is used as a main selection filter. The main board is designed for a transceiver for amateur radio bands 160...40 M.

Fundamental electrical diagram The main board of the transceiver is shown in Fig. 1.

In receive mode, the signal from the bandpass filter is supplied to pin 3 of the board, and then, through matching transformer T1, to the input of the first mixer DA1. The signal from the smooth range generator (VFO) is supplied to pin 6 of the microcircuit through the contacts of relay K1. The mixer load is an electromechanical filter (EMF) of the upper or lower sideband intermediate frequency Z1. The EMF is connected through a balun transformer T2. The cascade on the field-effect transistor VT4 provides amplification of the intermediate frequency (IF) signal. From the output of the amplifier, the signal goes to the second mixer (DA2). Through the contacts of relay K2, a signal from a reference frequency generator of 500 kHz is supplied to pin 6 of the microcircuit. The low-frequency audio signal is fed through a simple low-pass filter using C23R25C28 elements to the DA4 audio amplifier, assembled on an LM386. The amplifier is covered by an AGC circuit. The detected audio signal controls the resistance of the drain-source transition of transistor VT6, thereby providing adjustment of the audio signal level at the input of the DA4 chip. The output of the microcircuit is loaded onto a resistor - a volume control with a resistance of 100-680 Ohms. Low-impedance headphones are connected to the resistor motor.
To switch to transmission mode, a voltage of 12 V is applied to pins 6 and 9 of the board. In this case, relays K1 and K2 are activated and the microphone amplifier on transistor VT2 is turned on. The electret microphone is connected to pin 1 of the main board. Sound signal from the output of the microphone amplifier goes to the first mixer DA1. Resistor R4 serves for precise balancing of the mixer in transmit mode. On pin 6 The mixer receives a 500 kHz signal from the reference oscillator through the contacts of relay K1. The generated IF signal with a suppressed carrier is sent to the EMF, where the non-working sideband and, additionally, the remainder of the carrier are suppressed. On the pin. 6 DA2 receives a VPA signal. From the output of the microcircuit, the amateur band signal goes to pin 10 of the main board and then to the bandpass filters of the transmitter. The input of the audio amplifier DA4 in transmit mode is short-circuited by the open junction of transistor VT5. The reference frequency generator is assembled on transistor VT1 according to a capacitive three-point circuit. The 500 kHz signal is removed from capacitor C10 to the emitter follower on transistor VT3. The mixer chips and the reference oscillator are powered by a separate DA3 stabilizer.
Details and design.

The main board is assembled on a PCB board with double-sided metallization. The dimensions of the board are 52.5x120 mm (Fig. 2).

The top layer of metallization serves as a screen and is connected to the “negative” terminal of the power source. Metallization around holes not connected to the negative is removed. The arrangement of elements on the printed circuit board is shown in Fig. 3.

The design of the main board uses constant resistors such as S1-4, S2-23, MLT; tuning – SP4-1A. All permanent capacitors – K10-17, KM; electrolytic – K50-35. Transformers T1...T3 are made on K7x4x2 rings with a permeability of 600NN. The number of turns is indicated in the diagram. Winding is carried out with a wire with a diameter of 0.25 mm. The coils are placed in the screen. Relays K1 and K2 - RES49 with a winding resistance of 270 Ohms. Choke L2 is small-sized, with an inductance of 100 μH. Such chokes were used in domestically produced VCRs. Electromechanical filter - FEM4-52-500-2.75 or FEM4-52-500-3.1 with upper or lower side strip, manufacturer - Avers company.
Path setup.

The main board connection diagram is shown in Fig. 4.

A correctly assembled board in receive mode does not require configuration. In transmit mode, use R4 to set the maximum carrier suppression.
If necessary, using R13, the transmission coefficient of the microphone amplifier is selected so that even when loud sounds are uttered in front of the microphone, signal clipping does not occur. The signal shape can be monitored using an oscilloscope at the output of the power amplifier. If a dynamic microphone is used, elements R1, R2, R5 and C2 do not need to be installed. The optimal amplitude of the GPA voltage at pin 4 of the main board is 150…200 mV.
In transmit mode on pin 10 of the main board, the level of the useful SSB signal is 20-50 mV into a 50 Ohm load.
You can take a printed circuit board in Sprint Layout 5 format.

Appearance The assembled main board is shown in the photo.

Literature
1. Double balanced mixer SA612A. Radio, No. 4, 2004, pp. 48-49.
2. Transceiver "Amator-EMF". Radioamator, No. 11, 1996, pp. 18-19
3. Transceiver “Amator-EMF-U”. Radiohobby, No. 5, 2000, pp. 33-38.
4. Main board of the "Amator-EMF" transceiver. Radiohobby, No. 6, 2007, pp. 37-38.

UR5VUL Alexey Temerev Svetlovodsk, Ukraine. 2008

In the September issue of Radio magazine last year a description of the “Amator-160” transceiver, easy to manufacture and configure, with an EMF as the main selection filter was published. Experience has shown that radio amateurs have difficulty purchasing such a filter. Using the circuit solutions of one of the previous designs - the Amator-KF transceiver - it was possible to create a simple device with a homemade quartz filter(“Amator-KF-160”), designed for SSB operation on the 160-meter range. The author hopes that the proposed version takes into account all the shortcomings inherent in the prototype, and that no new ones have appeared.

Basic parameters of the transceiver: sensitivity at a signal-to-noise ratio of 12 dB - no worse than 1 µV; selectivity over adjacent and other side reception channels - no worse than 60 dB; adjustment depth of the AGC system - at least 60 dB; peak output power of the transmitter at a load of 50 Ohms - no less than 5 W; suppression of spurious emissions in transmission mode - no worse than 40 dB; current consumption in transmission mode is no more than 0.6 A at a supply voltage of 12V.

Thanks to the use of integrated circuits, it became possible to create a compact transceiver that does not have scarce components and is easy to configure. Of course, such a device does not have very high parameters, but it can be recommended either as a transceiver for a beginning shortwave radio amateur, or as a mobile auxiliary transceiver.

The reversible path of the transceiver is implemented on two K174XA2 microcircuits. From the composition of the microcircuits, only adjustable amplifiers, mixers and UPT systems of the AGC UFC were used. The adjustable amplifiers of the microcircuits themselves are not used, since they have a high noise figure and are not designed to operate at frequencies above 1 MHz.

Structurally, the transceiver is divided into three components: the main board (Fig. 1), a smooth range generator (Fig. 2) and a power amplifier (Fig. 3). The interconnection diagram of the transceiver is shown in Fig. 4.

Rice. 1

In reception mode, the signal from the antenna input through contacts KZ.2 of the KZ relay located in the PA unit is supplied to pin 3 of the main board. A double-circuit bandpass filter (DFT) is assembled using elements L1C4C6C8L4. The radio frequency signal, having passed through the DFT, arrives at the input of the DA1 microcircuit. In this microcircuit, the signal is amplified and converted to an IF frequency. The GPA signal is supplied to pin 6 of the main board and through contacts K1.1 of relay K1, transformer T1 is supplied to the DA1 chip. The L5C19 circuit connected to the converter output of the microcircuit is configured to the IF frequency. A six-resonator crystal filter Z1 is connected to the tap of inductor L5, which provides optimal matching. The filter circuit is shown in Fig. 5. From the output of the quartz filter, the IF signal goes to the DA2 chip. The reference oscillator signal arrives at this microcircuit through contacts K2.1 of relay K2 and transformer T2. The audio frequency signal is isolated at resistor R15. Low-pass filter C27R19C28 attenuates high-frequency components of the detected signal. The audio amplifier is assembled on the K174UN14 integrated circuit in a standard connection. Its gain is 40 dB. From pin 11 of the main board, signal 34 goes to the headphones through the volume control R1 (see Fig. 4).

The receiving path is covered by an AGC system. The signal for the operation of the AGC system is removed from the output of the ultrasonic sounder and through resistor R23 is supplied to the VD7VD8 detector. The speed of the system is determined by the capacitance of capacitor C29. From the output of the emitter follower VT3, the AGC voltage is supplied to the amplifier direct current(UPT) of the S-meter (pin 9 of the DA2 chip) and through the VD4 diode to the control inputs of the DA1 and DA2 chips. The diode is installed so that in transmit mode the control voltage does not affect the S-meter.

Rice. 2

Fig.3

Rice. 4

Rice. 5

The voltage to the S-meter is supplied from pin 13 of the main board through trimming resistor R22 and diode VD9, connected to pin 10 of the DA2 chip.

The reference frequency generator is assembled on a field-effect transistor KP303G(VT1). The frequency of the ZQ1 resonator is 8.867238 MHz. By adjusting the inductor L2, you can shift the oscillation frequency of the generator within small limits relative to the passband of the quartz filter. The source follower on transistor VT2 eliminates the influence of the load on the oscillation frequency of the generator.

The transceiver is switched to transmit mode by pressing the SB1 ("Control" button) connected to the XS3 connector. In this case, the short-circuit relay in the UM block is activated. This relay, depending on the operating mode, with its contacts KZ.2 connects the antenna either to the input of the receiving path or to the output of the transmitter and at the same time with the contacts KZ.1 switches the necessary supply voltages of the transceiver units. Voltage +12 V (TX) is supplied to pins 4 and 12 of the main board, relays K1, K2 are activated and the GPA and reference oscillator signals are switched. From pin 12, voltage is supplied to the inverse input of the DA3 ultrasonic microcircuit and blocks it. The supply voltage is also supplied to the electret microphone VM1 (see Fig. 4). The signal from the microphone is supplied to the DA1 chip through the low-pass filter C5L3C10, which prevents high-frequency interference from penetrating the input of the microphone amplifier. In transmit mode, the DA1 chip operates as a balanced modulator. The reference oscillator signal is supplied through transformer T1. The output of the modulator generates a two-sideband signal with suppressed carrier (DSB). Maximum carrier suppression occurs when the modulator is precisely balanced with trimming resistor R10. From the output of the DSB modulator, the signal is fed to a quartz filter, which selects the lower sideband. The DA2 chip converts the IF signal into a 160-meter amateur band signal. The high-frequency load DA2 is the broadband transformer TZ, which matches the high output impedance of the mixer with the low load impedance. The RF signal from pin 9 of the main board enters the power amplifier. The transmission coefficient of the path is adjusted by resistor R3 “TX Level”. The maximum transmission coefficient corresponds to the minimum voltage at pin 8 of the main board.

In the PA block, the signal passes through a dual-circuit bandpass filter L7C53C54C55L8, amplified by a pre-final amplifier on transistors VT6, VT7 and a final stage on VT8.

An imported 2SC2078 was selected as the output transistor. This transistor is usually used in the final stages of CB radio stations in the 27 MHz range and develops a power of at least 4 W at a supply voltage of 12 V. As it turns out, it is easy to purchase on radio markets in major cities. In the range of 160 meters, you can easily get 5 W of peak power from this transistor. Chain R37VD11 R38 sets the initial bias current of the transistor in transmit mode so that it operates in linear mode. Boosted signal through the contacts KZ.2 enters the antenna. From the divider R39R40, part of the output signal voltage is supplied to the level detector. The voltage rectified by the detector is supplied to the PA1 indicator.

Transceiver "Amator-EMF-SA"

The proposed main transceiver board uses imported SA612 microcircuits. EMF is used as a main selection filter. The main board is designed for a transceiver for the amateur radio bands of 160, 80, and 40 meters.

Schematic diagram of the main board

To switch to transmission mode, a voltage of 12 V is applied to pins 6 and 9 of the board. In this case, relays K1 and K2 are activated and the microphone amplifier on transistor VT2 is turned on. The electret microphone is connected to pin 1 of the main board. The audio signal from the output of the microphone amplifier goes to the first mixer DA1. Resistor R4 serves for precise balancing of the mixer in transmit mode. On pin 6 The mixer receives a 500 kHz signal from the reference oscillator through the contacts of relay K1. The generated IF signal with a suppressed carrier is sent to the EMF, where the non-working sideband and, additionally, the remainder of the carrier are suppressed. On the pin. 6 DA2 receives a VPA signal. From the output of the microcircuit, the amateur band signal goes to pin 10 of the main board and then to the bandpass filters of the transmitter. The input of the audio amplifier DA4 in transmit mode is short-circuited by the open junction of transistor VT5. The reference frequency generator is assembled on transistor VT1 according to a capacitive three-point circuit. The 500 kHz signal is removed from capacitor C10 to the emitter follower on transistor VT3. The mixer chips and the reference oscillator are powered by a separate DA3 stabilizer.

Details and design.

The main board is assembled on a PCB board with double-sided metallization. Board dimensions 52.5x120 mm.

The top layer of metallization serves as a screen and is connected to the “negative” terminal of the power source. Metallization around holes not connected to the negative is removed.

Path setup.

A correctly assembled board in receive mode does not require configuration. In transmit mode, use R4 to set the maximum carrier suppression.

If necessary, using R13, the transmission coefficient of the microphone amplifier is selected so that even when loud sounds are uttered in front of the microphone, signal clipping does not occur. The signal shape can be monitored using an oscilloscope at the output of the power amplifier. If a dynamic microphone is used, elements R1, R2, R5 and C2 do not need to be installed. The optimal amplitude of the GPA voltage at pin 4 of the main board is 150…200 mV.

In transmit mode on pin 10 of the main board, the level of the useful SSB signal is 20-50 mV into a 50 Ohm load.

UR5VUL Alexey Temerev

Transceiver "Amator-160"

The transceiver is designed for radio communications in the 160m range and has the following parameters:

Operating frequency range 1800-2000 kHz;

Type of work - SSB.;

Sensitivity at a signal-to-noise ratio of 10 dB, no worse than 1 µV;

Selectivity in the mirror channel, no worse than 40 dB;

Range of manual gain adjustment, not less than 60 dB;

Peak output power of the transmitting path, not less than 5 W (at a load of 50 Ohms);

Suppression of side channels in transmit mode, no less than 40 dB.

The reversible path of this transceiver uses K174PS1 microcircuits, which are active balanced mixers with a high conversion slope. Thanks to their use, the transceiver path has been significantly simplified - the number of winding units has been reduced, and it has become possible to do without an IF path and a separate microphone amplifier.

Functionally, the transceiver is divided into four boards - the main board, the rectifier board, the GPA and the final transmitter power amplifier. The main board contains the reversible transmit-receive path itself, a 500 kHz reference oscillator, an audio amplifier, receive and transmit bandpass filters, as well as a transmitter power pre-amplifier.
Description of the transceiver operation.
In the receiving mode, the RF signal through the contacts of relay K1.2 enters the main board, where it is isolated by a dual-circuit bandpass filter based on elements L3С12С13С14L5 and is fed to the input of the DA2 mixer. The second input of the mixer receives a GPA signal through relay contacts K2.1 and broadband transformer T2. The mixer load is EMF Z1 (EMF-9D-500-3V). The selected IF signal of the desired sideband is fed to the DA3 mixer. A reference oscillator signal is supplied to the second input of the mixer through relay contacts K3.1 and broadband transformer T3. The 500 kHz reference oscillator is made on transistor VT2 according to a three-point capacitive circuit. Zener diode VD7 serves to stabilize the generator supply voltage. The audio frequency signal, isolated by the mixer load (R10), is fed through a simple low-pass filter using elements C34R15С37 to the audio amplifier chip DA4 (K174UN14). Both headphones and a loudspeaker can be used as the BA1 terminal device. The volume of the received signal is regulated by resistor R4 “RX Level”. When the resistor motor rotates, the supply voltage of the DA2 microcircuit changes and, consequently, the conversion slope also changes. This solution may not be the most optimal from a circuit design point of view, but it is quite applicable for simple devices. The manual gain control range measured by the author was more than 60 dB. The supply voltage is supplied to the output transistor of the final power amplifier VT1 all the time, but it is switched to the active operating mode only in the transmission mode by applying a bias voltage. To switch to the transmission mode, press the S2 button. In this case, relay K1 is activated, with the help of which the necessary switching is performed. +12V voltage is supplied to pins 4, 10 and 11 of the main board and to pin 2 of the final power amplifier. Through resistor R4, power is supplied to the electret microphone. Through resistor R5 and diode VD5, supply voltage is supplied to the DA2 chip, bypassing the gain control unit. Relays K2 and K3 are activated and the GPA and reference oscillator signals change places. In addition, the +12V voltage through resistor R17 and diode VD8 is supplied to the inverse input of the ultrasonic microcircuit, blocking its operation. The constant voltage at pin 4 of the microcircuit drops to zero. The power supply voltage is also supplied to the transmitter power preamplifier. The transistor of the final power amplifier is switched to active mode. The electret microphone signal goes to the DA2 mixer chip. The low-pass filter on the C11L4C15 elements prevents high-frequency interference from penetrating the microphone input of the transceiver. In this case, the second input DA2 receives a signal from the reference oscillator. Maximum suppression of the reference frequency signal is achieved by precisely balancing the mixer using potentiometer R6. The EMF selects the signal of the desired sideband and further attenuates the remaining carrier. The DA3 chip converts the IF signal into a 160m amateur radio signal.

The load of the mixer during transmission is DPF С31L6С32L7С35. A transmitter power pre-amplifier is assembled using transistors VT3 and VT4. From the output of the main board, the radio frequency signal goes to the final power amplifier board. The final amplifier is assembled using a KP901A field-effect transistor. The output signal enters the antenna through a single-link low-pass filter. The transmitter output filter is designed to operate with a 50 Ohm active resistance load. To monitor the RF signal at the transceiver output, a simple detector is used (resistive divider R31R32, diode VD12 and microammeter PA1). The GPA of the transceiver is made on a bipolar transistor according to the capacitive three-point circuit on the VT5 transistor. Transistor VT6 is a buffer emitter follower of the GPA signal. The power supply provides a stabilized voltage of +12V and an unstabilized voltage of +34V (to power the final stage of the transmitter).
Transceiver parts.
The transceiver uses: Fixed resistors – type C1-4, C2-23, MLT; trimming resistors - SP3-38B. Non-electrolytic capacitors - K10-17, trimmers - type KT4-23. Electrolytic capacitors – K50-35. A KPI from a tube radio receiver was used as a tuning capacitor. The network transformer must have an overall power of at least 50 W and provide 2x13 V alternating voltage in the secondary winding at a current of 1.5 A. The author used a transformer from the “Do it yourself transformer” amateur radio kit. Broadband transformers T2 and T3 are manufactured on K7x4x2 ferrite rings with a permeability of 600-1000 NN. The windings are wound in two wires and contain 2x20 turns of PEV 0.25. Chokes L4 and L8 are standard DM-0.1, L1 – D-0.6. The inductance of all chokes is 100 μH. DPF coils are made on SB9 armored cores and contain 30 turns of PEV 0.15 wire. The tap of the L3 coil is made from the 6th turn (counting from the grounded end); at L5 – from the middle. The low-pass filter inductance of the L2 transmitter is made on a ferrite binocular core from balancing devices used in domestic televisions. Winding is carried out with a single-core wire with a diameter of 0.4 mm in PVC insulation, the turns of the wire are passed through the internal holes of the core. The number of turns is 8. The L9 GPA coil is made on a frame made of heat-resistant plastic with a diameter of 12 mm with a tuning ferrite core and contains 40 turns of PEV 0.6 wire. Relay K1 - RES9 with a winding resistance of 500 Ohms (you can use any suitable relay with two groups of switching contacts. Relays K2 and K3 -RES49 with a winding resistance of 270 Ohms. You can also use relays with a higher operating voltage by connecting them in parallel. VM1 - imported electret "tablet" microphone PA1 - pointer microammeter with a total deviation current of 50 - 100 µA.

The transceiver components are assembled on boards made of double-sided foil PCB, the top layer of metallization serves as a screen.

The transceiver is assembled in a duralumin housing with dimensions 220x220x110, divided by a partition into two compartments - upper and lower. In the upper (larger) compartment there is a network transformer T1, a GPA board, a KPI, a rectifier board, a PA board, a K1 relay and a DA1 stabilizer. The transistor of the final amplifier VT1 and the stabilizer DA1 are screwed to the rear wall of the case, which acts as a radiator. The PA board is also mounted on the back wall on racks. The high-frequency detector is assembled using the volumetric mounting method and is located in close proximity to the antenna connector, also near the K1 relay connector. The main board is installed in the lower compartment of the case. The adjustment scale is a plexiglass disk with marked marks, attached directly to the KPI axis.
Setup.
Configuring the transceiver begins with the GPA unit. By adjusting the L9 coil and selecting the C46 capacitance, the operating tuning range of the GPA is set within the range of 2300-2500 kHz with some margin (10-20 kHz) at the edges of the range. The output level of the GPA should be in the range of 100-200 mV. After this, they begin to configure the main board. First of all, you need to make sure that the reference oscillator is working by connecting, for example, an oscilloscope probe to the emitter of transistor VT2. By applying a high-frequency generator signal to the transceiver input, the input DFTs are adjusted, after which, by adjusting C20 and C21, the maximum volume of the received signal is achieved. If you don’t have a generator, you can use signals from amateur radio stations for tuning.

Further configuration of the transceiver is carried out in transmission mode with the final stage turned off. Potentiometer R6 is used to balance mixer DA2, achieving maximum suppression of the reference oscillator signal. Balancing control is best done with an oscilloscope or a high-frequency millivoltmeter at the output of the EMF. If even with precise balancing of the mixer it is not possible to suppress the carrier within the required limits, it is necessary to reduce the voltage of the reference oscillator by increasing the value of resistor R7. By applying an audio frequency generator signal with an amplitude of 3-5 mV and a frequency of 500-1000 Hz to the microphone input of the transceiver, the DFT of the transmitter is adjusted. An RF millivoltmeter or oscilloscope is connected to the output of the main board (pins 11, 12) and by adjusting L6 and L7 the maximum readings are achieved in the operating frequency band. The preliminary stage of the transmitter must develop a voltage of at least 5V into a load of 500 Ohms. Before connecting the final stage of the transmitter, it is necessary to set the quiescent current of transistor VT1. Without supplying a high-frequency signal to the final stage, adjusting R2 ensures that the quiescent current of the transistor is in the range of 200-220 mA. The current is monitored with a milliammeter via the +34V circuit. The final stage of setup is monitoring the transmitter output power. Having connected all the components of the transmitter, connect a matched load to the antenna connector of the transceiver. A 5 mV-1000 Hz audio frequency generator signal is supplied to the microphone input. Using a millivoltmeter or oscilloscope, the voltage across the matched load is monitored in transmission mode. The voltage should be within 15-18 V. The current consumption of the final stage in the +34V circuit should be within 0.4A. Greater unevenness of the output power in the operating frequency range can be reduced by additionally adjusting the DFT of the transmitter and the low-pass filter of the final stage. By selecting R30, we ensure that the power indicator needle is in a sector of the scale that is convenient for observation.
The final stage of this transceiver is designed to work with antennas having a resistance of about 50 Ohms. When operating the transceiver with random antennas, it is necessary to use a matching device.