Transceiver for 160 meters. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Civil radio communications

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This transceiver is designed to operate on the 1850...1950 kHz band in both CW and SSB modes. The sensitivity of the transceiver is no worse than 5 μV. The bandwidth at the level of -6 dB when working by telegraph is 1 kHz, by telephone - 3 kHz, and at the level of -60 dB - no more than 4 and 5 kHz, respectively. During transmission, a power of 5 watts is supplied to the output stage. The output power of the transceiver is at least 2 watts. In SSB mode, the lower sideband is emitted. The carrier frequency and upper sideband are suppressed by at least 50 dB.

The transceiver has a built-in antenna tuner with an SWR meter.

Schematic diagram transceiver is shown in fig. 1. When transmitting in CW mode, power is supplied through the contacts of switch S5.1 to a 501 kHz frequency generator assembled on a 3VI transistor. When you press the telegraph key, the signal from the generator goes to the EMF ZI. and from it to the gate of the 2V2 transistor, which is a mixer in the transmission path. The source of this transistor is supplied with voltage from the GPA (transistor 2V6 - generator, 2V5 - emitter follower), covering the section 2351 ... 2451 kHz. The circuit in the drain circuit of the 2V2 transistor with capacitor C8 is tuned within 1850 ... 1950 kHz and selects the difference conversion frequency.

Schematic diagram of the transceiver (part 1), 40 kb
Schematic diagram of the transceiver (part 2), 42 kb

The CW signal is fed through switch S4.1 to the 2VI transistor power preamplifier and then to the final amplifier on V4. When working on the reception, the transistor V4 is closed, since in this case a positive bias voltage is not applied to its base.

From the final stage, the signal enters the antenna through a matching device. It consists of elements L1 and C1. Depending on the position of switch S1, this device is switched on in one of three ways. The presence of several options for turning on the matching device and the ability to adjust the elements L1, C1 make it possible to match the transceiver well with most types of antennas.

The quality of the tuning of the antenna-feeder path is controlled using an SWR meter. assembled on elements 1R1-1R4, 1V1, 1C1, 1C2 and PA1.

When transmitting in SSB mode, power is removed from the 501 kHz frequency generator and fed to an amplifier based on a 3V8 transistor.

The signal from the microphone is amplified by transistors 4V3-4V1 and through the contacts of the switch S5.2 and S4.2 (only when transmitting and only in SSB mode) is fed to a ring balanced modulator on diodes 3V3-3V6 (when receiving, it plays the role of a mixer). The reference oscillator is assembled on a 3V2 transistor. The frequency of this generator is determined by the quartz resonator B1, and is equal to 500 kHz. The two-sideband suppressed carrier signal is amplified by the 3V8 transistor and then fed through the 3V7 diode to the EMF, which highlights the upper sideband. At the output of the mixer (transistor 2V20), a signal with a lower sideband is formed, which is then fed through switch S4.1 to the preamplifier, and then to the power amplifier.

When working on reception, the signal from the antenna through the matching device enters the gate of the 2V3 transistor, which acts as a mixer. The signal from the GPA is fed to the source of the same transistor. The converted signal, which lies in the frequency band of 500...503 kHz, passes through the EMF Z1 and is amplified by transistors 3V10, 3V11, connected in a cascode circuit. From the load of the cascode amplifier. - circuit 3C14L8 the signal is fed to the balanced mixer. A voltage with a frequency of 500 kHz from the reference oscillator also comes here.

A low-frequency amplifier is assembled on transistors 4V4-4V7. When transmitting in SSB mode, the power supply to the last two stages of the amplifier will not be applied.

The transceiver is turned on with switch S3, which, simultaneously with the power supply, switches the device to the SWR measurement mode, and then to work on the air.

The transition from reception to transmission is made by switch S4.

The power supply provides a constant voltage of 30 V - stabilized (for the output stage) and 15 V (for the remaining stages).

The transceiver (its dimensions are 310x120x225 mm) is assembled on a chassis 28 mm high, to which the front and rear panels are screwed, and a gap of 30 mm is left between the front panel and the chassis. The design of the transceiver is shown in Fig.2.

Fig.2. Front Panel

Chassis top view
Chassis bottom view

Most of the details are placed on printed circuit boards (Fig. 3-6). The color on them shows the conductors located on the underside of the boards. It is possible to make boards using mounting racks connected from below by conductors, providing petals under each hole for attaching the board to the chassis.

Fig.3. Printed circuit board
Fig.4. Printed circuit board
Fig.5. Printed circuit board
Fig.6. Printed circuit board

All switches in the transceiver are ceramic, elements C1 and C8 are dual variable capacitors with an air dielectric. C1, C5, C6 must be isolated from the transceiver case. The block of capacitors is installed on a fiberglass board, and a textolite nozzle is put on the axis.

Capacitor C8 is rebuilt with a vernier consisting of a disk with a diameter of 70 mm, with a frequency scale printed on the end, and an axis with a tuning knob connected by a nylon cable, the tension of which is provided by a spring located in the disk.

Coil L1 is wound on a frame with a diameter of 28 mm with PEV-2 0,55 wire. It consists of ten sections of 5,5 turns each. The total winding length is 32 mm.

The 1L1 coil is wound on a frame with a diameter of 9 mm with PEV-2 0,35 wire and contains 60 turns. Winding length 26 mm.

The coils of the L6 and L7 generators are made on plastic frames with a diameter of 16 mm. To ensure the required frequency stability of the generators, the frame material must have a low thermal expansion coefficient (for example, good results were obtained when using frames made of AG-4, polystyrene, plexiglass can be used, but the use of fluoroplastic is completely unacceptable). The L6 coil is wound with PEV-2 0,35 wire and contains 45 turns, the winding length is 18 mm. L7 is wound with PEV-2 0,23 wire and contains 82 turns, the winding length is 20 mm.

Coils L2 and L3, L4 and L5, L8 and L9 are made in SB-12a cores. L2 and L4 each contain 25 turns of PESHO 0,31 wire. The coupling coils are wound with the same wire, L3 contains 4 turns, L5 - 3 turns. L8 and L9 are wound with PEV-2 0,1 wire and contain 150 and 30 turns, respectively.

All three SB-12a cores with coils are placed in screens with a diameter of 20 and a height of 25 mm.

Transistor V4 and diodes V1, V2 are attached directly to the chassis, and the zener diode V3 is attached through an insulating mica gasket 0,1 mm thick.

Set up the transceiver start with the power supply. The rectifier output should have a voltage of 36 V, and with a load (150 Ohm resistor) - 32 V. The stabilized voltage, depending on the type of zener diode used, can be in the range of -14 ... -16 V and should decrease by no more than by 0,5 V when a load is connected (with a resistance of 150 ohms). DC transistor modes are shown in the table.

To eliminate the influence of high frequency, voltages were measured with coils L6 and L7 disconnected from the boards and resonator B1 (generators do not work). All voltages are measured relative to the case at a stabilized supply voltage of 15 V.

The required frequencies of the generators are set by trimmer capacitors C11 and C 12. If this cannot be done, capacitors 2C19 and C9 should be selected. The stability of the generators should be considered normal if the frequency deviation does not exceed 100 Hz per hour of operation of the transceiver after switching on. Such stability is ensured with the correct execution of the coils L6 and L7 and the use of blue KSO group "G" or KTK-2 capacitors in the circuits. If the oscillator frequency changes stably in one direction when the transceiver warms up, it is necessary to use a 2C19 (C9) capacitor with a different TKE. The RF voltage at the emitter of the transistor 2V5 should be 1 ... 1.2 V. at the emitters 3VI and 3V2 - 0,8 ... 1 V.

The low-frequency amplifiers of the receiver and transmitter, when a signal with a level of 5 mV is applied to their inputs, must provide a voltage of at least 0,5 V at the output. The frequency characteristics of the low-frequency amplifiers of the transmitter and receiver in telephone mode must be uniform in the range of 300 ... the receiver bass amplifier in CW mode must have a maximum frequency response at a frequency of 3000 Hz with a signal attenuation of at least 1000 times at frequencies of 2 Hz and 700 kHz.

When transmitting in CW mode with the key pressed, controlling the voltage at the EMF output (pin 5 on board 2), it is necessary to select capacitors ZS15 and 2C11. achieving the maximum of this voltage (0,2 ... 0,3 V).

When transmitting in SSB mode, tune the 3C14L8 circuit. In this case, you must first unbalance the modulator (the engine, resistor R3 should be set to any extreme position), and then adjust the L8 coil, achieving the maximum voltage (2.5 ... 3,5 V) at the EMF input (pin 4 board 3). By adjusting the resistor R3, the modulator is balanced. The voltage at the EMF input should decrease in this case to a value less than 0.1 V.

By controlling the voltage at the EMF output (pin 5 of board 2), it is advisable to check the end-to-end frequency response of the SSB signal generation path by applying a low-frequency signal of 5 mV to the microphone input of the transceiver. The voltage at the EMF output should vary within 0,2 ... 0,35 V when the frequency changes from 500 to 3000 Hz and decrease by 30 ... 50% when the frequency drops to 300 Hz. The required frequency response is set by selecting the capacitor C2, which corrects the frequency of the reference oscillator.

The power amplifier is checked in telegraph mode with the key pressed. Switch S3 must be in the "Operation" position. An equivalent load with a resistance of 75 ohms is connected to the output of the transceiver and, by adjusting the coils L4 and L3, the maximum reading of the indicator is achieved at the middle frequency of the operating range. Deviation of the indicator needle to 80...100 mA corresponds to a voltage at the load of 12...14 V, i.e., the output power will be 2...2,8 W. When working on a matched load, switch S1 must be in position "I" or "II", and the inductance and capacitance of the matching circuit must be minimal. When the key is released, as well as when switch S3 is moved to the "SWR" position, when the key is pressed, the indicator should show "0".

When working on reception, a signal with a level of 5 μV must be confidently received, applied to the input of the transceiver through a 75 Ohm resistor.

Work on the transceiver. The transceiver is designed to work with a dynamic microphone and headphones with an impedance of 200 ..2000 Ohm.

On a range of 160 m, a sufficiently large antenna is required - the minimum length of its radiating part is about 30 m. The antenna must be coordinated with the transceiver, for this, switch S3 is set to "SWR", S5 - "CW", and with the key pressed, adjusting the matching circuit (type of circuit, capacitance, inductance). it is necessary to achieve a minimum of indicator readings. An agreement should be considered satisfactory if the indicator deviates by no more than 20 μA.

When using a telephone, transmission is automatically performed on the frequency of the correspondent. When working with the telegraph, it is necessary, when receiving, to tune in to a tone that matches the tone of the self-control signal.

Author: Ya. Lyapovok (UA1FA); Publication: N. Bolshakov, rf.atnn.ru

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