Master oscillator.
To achieve frequency stabilization in the control grid, it is necessary to use KSO capacitors of group G + -5%. The circuit is wound on a frame with a diameter of 20 mm, with a wire of 0.8 mm diameter, 40 turns.
Buffer cascade
Everything is clear from the diagram. It can be simplified by removing Dr2 and everything else that goes with it. Place one 27k resistance from the control grid to ground. You can also apply modulation to one terminal of the transformer directly to the 3rd leg, and the other to ground, removing everything else. The modulator must be a tube one and produce 200 volts or more at the output of the modulation transformer; you can use the TC-180 from old tube TVs. 
Output stage
Dr1 is wound with 0.23-0.35 mm wire on a ceramic frame with a diameter of 10-15 mm, four sections of 80 turns per pile. Dr2 is wound with three wires on a thick ferite rod (from any receiver where there is a magnetic antenna) filament wire 1.0-1.5mm, cathode 0.5mm. It is wound until it is completely filled, leaving room for its attachment. The circuit is wound on a frame with a diameter of 50 mm with a 2.0 mm wire of 35-38 turns. For a more complete calculation of the P-contour, you can use the program: click here 
Antenna
The antenna used with this “American” transmitter has a length of 48 m with a 1.6 mm wire and a reduction of 12 m with a 1.0 mm wire. The reduction is connected at a distance of 1/3 from the hot end. 
But you can use any other antenna you like!
The transmitter of the second category is designed for half-duplex telegraph communication on the ranges of 10, 20, 40, 80 m and simplex telephone communication on the ranges of 10 and 80 m. The power supplied to the anode circuit of the output stage is 40 watts.
The schematic diagram of the transmitter is shown in the figure in the text.
The transmitter consists of four stages of the high-frequency path (master oscillator, multiplier buffer, doubler amplifier, final amplifier), modulator and rectifiers.
The master oscillator, assembled on lamp L3, operates in the range of 80 m. To increase frequency stability, the screen grid voltage is stabilized using a zener diode L2, and capacitors C20, C24 and C27 with different temperature coefficients are included in the oscillatory circuit of the generator. The frequency of the master oscillator is set by the first section of the dual variable capacitor C21a.
The transmitter is manipulated through the control grid circuit of the master oscillator lamp: when the key is released, a blocking voltage of 75 V is applied to the lamp grid through resistors R26, L25. When the key is pressed, a zero potential is applied to the grid through resistor R25, the lamp is unlocked and the generator is excited.
The excitation voltage for the next stage is removed from the inductor Dr2 through the transition capacitor C38; this stage is made on the L4 lamp and operates in buffer-amplifier mode when operating on the 40 and 80 m ranges and in the buffer-multiplier mode when operating on the 20 and 10 m ranges. In the first case, the inductor Dr4 is connected by relay contacts P1/1 to the lamp anode in series with the L2C34C35 circuit. On the 40 and 80 m ranges the circuit turns out to be detuned, and the role of the input load is performed by the choke. When operating on the 20 and 10 m ranges, relay P1 switches inductor Dr4 into the lamp anode power decoupling circuit. In this case, the 4th harmonic (20 m) of the master oscillator is allocated on the L2C34C35 circuit. To better isolate this harmonic, the circuit is adjusted with capacitor S21b (the second section of the block of variable capacitors) simultaneously with setting the frequency of the master oscillator.
The third stage is made on an L5 lamp, which operates, depending on the range, either in amplification mode or in doubling mode. On each band, a separate circuit is connected to the anode of the lamp using switch P3: on the 80 m range - circuit L3C42, while the lamp operates in the oscillation amplification mode; on the 40 m range - circuit C4C43 the lamp operates in doubling mode; on the 20 m range - L5C44 circuit, the lamp operates in amplification mode; on the 10 m range - L6C45 circuit, the lamp operates in doubling mode. Using capacitor C46, each circuit is adjusted to obtain the required excitation voltage of the final stage, which is especially necessary when operating on the 20 and 10 m ranges. Negative bias is supplied to the control grid of lamp L5 from a voltage divider on resistors R46, R47.
From the anode of lamp L5, the excitation voltage through capacitor C48 is supplied to the grid of lamp L6 of the output amplifier, which operates in power amplification mode on all ranges. The anode load of this cascade is a P-circuit, consisting of coils L7 L5 and capacitors C55, C57. The coils are switched when moving from one range to another using relays P2 and P3. An electronic antenna switch is assembled on diodes D22 and D23, the use of which allows you to use the same antenna for the receiver and transmitter and operate in half duplex. A stabilized bias voltage is supplied to the control grid of lamp L6 through inductor Dr7 from gas-discharge stabilizer L1.
The modulator is assembled on transistors T1, T2 and lamp L7. It is designed to work as a dynamic microphone. The sensitivity of the modulator is no worse than 2 mV with uneven frequency response in the frequency band 300-3,000 Hz + 3 dB. Above 3,000 Hz, the modulator's frequency response drops sharply, resulting in a narrow emission bandwidth. The modulation depth is regulated by a variable resistor R34, on the axis of which the modulator switch Bk2 is installed. The transition from telegraph to telephone mode is carried out using switch P1. Modulation - on the pentode grid of the final stage.
To configure and control the operating mode of the transmitter, the IP1 device is provided. Using switch P4, it is connected either to the grid or to the anode circuit of the output stage lamp. In the first case, the device measures current up to 15 mA, in the second - up to 150 mA.
The transition from range to range is carried out with one handle - switch P3, with the help of which all the necessary switching of the relays and circuits of the pre-terminal stage is carried out.
To avoid radiation when tuning the transmitter to the correspondent frequency, the output amplifier is switched off at these moments using switch P2.
The transmitter is powered by four rectifiers. The anode voltage of 600V for the output lamp is removed from two series-connected rectifiers assembled on diodes D1-D16. In the 600 V voltage circuit, filter C2R9C3 is included. To power the anode and screen circuits of the remaining lamps, a rectifier based on D9-D16 diodes with filter C4, Dr1, C5 is used. A half-wave rectifier based on diode D17 with filter C6, R21, C7 is used to obtain bias voltage. A 24 V rectifier on diodes D18-D21 with a filter capacitor C8 serves to power the modulator and relay.
Details. The power transformer Tr1, choke Dr1, loop coils and high-frequency chokes of the transmitter are homemade. The transformer is assembled on a Sh-25 core, the thickness of the package is 50 mm. Winding data is given in table. 1.
| Winding | Number of turns | The wire |
| 1 | 935 | PEV 0.51 |
| 2 | 1050 | PEV 0.25 |
| III | 960 | PEV 0.41 |
| IV | 500 | PEB 0.15 |
| V | 85 | PEV 0.35 |
| VI | 54 | PEB 0,8 |
| VII | 28 | PEV 1.0 |
The Dr1 throttle is made on a Sh-15 core, the thickness of the package is 32 mm. It contains 1250 turns of PEV 0.38 wire.
Data for loop coils and high-frequency chokes are given in table. 2.
| Designation | Frame | |||||
| Number of turns | The wire | material | diameter, mm | Winding | Inductance, μgn | |
| L1 | 32 | palsho 0.51 | polystyrene | 18 | solid, one layer | 10 |
| L2 | 10 | PEV 1.0 | » | » | » | 1,5 |
| L3 | 46 | PEV 0.7 | » | » | » | 14 |
| L4 | 19 | PEV 1.0 | » | » | » | 4 |
| L5 | 10 | » | » | » | » | 1,5 |
| L6 | 4 | silver plated 2.9 | without frame | 20 | step 2 mm | 0.3 |
| L7 | 22 | » | » | 33 | step 1 mm | 5 |
| L8 | 7 | » | » | 35 | pitch 3 mm | 1,4 |
| DR2-DR8 | 200×4 | PELSHO 0.15 | textolite | 5 | station wagon | 3000 |
All fixed resistors are MLT type. You can use other resistors of appropriate resistance and power. Capacitors C2-C9, C13, C15, C18 - electrolytic; C1 type KBGI, KBGM with an operating voltage of at least 400 V; C10, C14 C16 – MBM type; S11, C12, S19, S39, S41, S49, S51, type BM-2; C17, C23, C28, C37, C38, C48, C56 - KSO type (C23 - preferably group G; C20, C24, C27, C35, C36, C42, C42, C44, C47, C58 - KT type C24 blue, C27 - Red); S25, S30, S32, S33, S40, S50 - type K40P; C53, C54 - SGM type; S22, S34 - type KPK-1; C21, C57 - standard twin units of any type; in C57, the fixed plates of both sections are connected in parallel; C46 - any type, this design uses KPV-140 with an extended axis; C55 - any type, with a gap between the plates of at least 0.8 mm, this design uses an antenna capacitor from the R-104 radio station.
Switches P1, P2, P4 toggle switches TP1-2, P3 - two-bar type 4P4N. Relay R1-type RES-6 (passport RF0.452.141) or RES-9 (passport RS4.524.201). P2, P3 - high-frequency of any type, for example from the RSB-5 radio station.
Measuring device - type M4203 with a scale of 15 mA or any other with the same total deflection current. Instead of one device, you can install two - in the grid and anode circuits - instead of resistors R48 and R51. In this case, switch P4 and resistors R48, R51, R52 are not needed.
Some kind of vernier should be installed on the axis of the capacitor unit C21. Scale - any type. In the design described, it is made on organic glass and illuminated from behind (with lamps JI8 and L9). A pointer is mounted on the vernier axis.
Zener diodes SG1P and SG16P can be replaced with SG4S and SG2S, respectively, transistors MP41 - with MP39 - MP42.
The design of the transmitter is shown on the 1st page of the tab. The transmitter is mounted on a horizontal chassis with dimensions 400X230X65 mm. The front panel with dimensions 400 X X 170 X 2 mm is fastened to the chassis with bolts and brackets. This makes it possible to install the transmitter in any position, which is convenient during assembly and installation. The cascades are separated from each other by partitions. The chassis, front panel and partitions are made of duralumin. The transmitter is placed in a detachable casing with holes for heat dissipation.
The rectifier elements, as well as resistors R18-R24, R40, R42, R44, R49, R50, R53, are mounted on two printed circuit boards, each of which is mounted on a power transformer (bottom and top). Most of the modulator elements are also mounted on a printed circuit board.
Methods for tuning transmitters were repeatedly described in detail in the Radio magazine, for example, in No. 10 for 1967 and No. 1 for 1968. All of them fully apply to this transmitter. It is only necessary to note the following. After checking the operation of the rectifiers, the master oscillator should be adjusted using the GIR or a precisely calibrated receiver. In this case, switch P2 should be in the “setup” position, P1 - in the telephone position.
The required frequency range of the master oscillator is set roughly by selecting the capacitance of capacitor C20 and precisely - C22. Then, by adjusting the capacitance of capacitor C34 and bending the plates of section C21b, circuit L2C34C35 is adjusted.
The third stage is adjusted according to the maximum reading of the IP1 device, connected to the grid circuit of lamp L6 with frequency control at the receiver or GIR. It is necessary to ensure that each circuit is tuned with capacitor C46 at the beginning, middle and end of its operating range. In this case, the device readings on the ranges of 80 and 40 m should reach 15 mA, on 10 and 20 m - 10-15 mA.
The output stage is tuned to the equivalent of an antenna (a resistor with a resistance equal to the characteristic impedance of the feeder and a power of at least 30 W, or an incandescent lamp). When switching to telephone mode, the anode current should drop by half compared to the telegraph mode.
The circuits can be used in equipment of the 1.9 MHz amateur band, officially approved for operation on the air by registered radio amateurs, i.e. having permission to operate an amateur radio station and a call sign. Some technical solutions from these schemes can be used in the design of amateur radio transmitters, or you can simply be nostalgic for the past - after all, the “radio hooligan youth” is behind the shoulders of many radio amateurs and just radio lovers.
Figure 1 shows a diagram of the simplest transmitting medium-wave set-top box with AM modulation for a radio receiver. The set-top box uses a 6PCS radio tube, the maximum power dissipation at the anode of which is 20.5 W.
Instead of a 6PCS, you can use a 6P6S lamp (maximum power dissipation at the anode is 13.2 W) - they have the same pinout.
The oscillatory circuit L1С1 is connected between the anode of the lamp and the control grid. It provides positive feedback of the cascade - one of the conditions necessary for self-excitation of the generator. Power is supplied to the lamp anode through an oscillating circuit (via a tap in coil L1). Switch SA1 is used to turn the cascade on in transmit mode and turn it off in receive mode.
The supply voltage comes from the anode of the output lamp of the ULF receiver, therefore, when a signal from the microphone is applied to the input of the ULF receiver, amplitude modulation of the HF oscillations generated by the attachment occurs.
Coil L1 is made on an ebonite frame with a diameter of D-30 mm and contains 55 turns of PEL-0.8 wire (turn to turn) with a tap from the 25th turn, counting from the bottom (according to the diagram) output. This attachment worked well, but had one drawback - the tuning capacitor C1 was galvanically connected to the anode of the lamp (and this is unsafe!), so the tuning knob had to be made of a dielectric.
Somewhat later, I managed to find a “organ organ” circuit (Fig. 2), devoid of this drawback. In it, a circuit is connected between the control grid and the cathode of the lamp. Moreover, partial inclusion of the cathode into the circuit due to tapping in the coil is used. This scheme is safer, but delivers slightly less power to the antenna than the previous one. Application of variable capacitor C1. allows you to optimally match the I-NW circuit with the antenna.
In this circuit, the 6PZS radio tube can also be replaced with a 6P6S. Coil I is wound on a ceramic mandrel with a diameter of D-32mm with PEL-0.7 wire. Number of turns - 50 (winding - turn to turn with a tap from the middle).
In Fig. Figure 3 shows a diagram of another “organ organ”. In it, KPI C2 is galvanically connected to the body through coil L2. If the terminals of this capacitor are accidentally shorted to the housing, nothing dangerous will happen - the generation of the RF signal will just stop.
The output power of this attachment is greater than that of the previous one (about the same as that of the circuit in Fig. 1), because The oscillatory circuit L2-SZ is connected to the lamp anode circuit. Throttle L1 is enclosed in a screen. Coil L2 is wound on a plastic mandrel with a diameter of D-30 mm with PEL-0.8 wire and contains 50 turns of wire wound turn to turn. The tap is from the middle of the winding.
Another schematic diagram of the simplest transmitting attachment on a 6PZS (6P6S) radio tube is shown in Fig. 4.
This circuit differs from the previous ones by the presence of inductor L1 in the anode circuit of the lamp, which made it possible to connect the output circuit to the anode. In this case, the stators of variable capacitors C2 and C5 are connected to a “common” wire, which significantly increases the safety of the device and makes it easier to control the setting elements. Switch SA1 is included in the cathode circuit of the lamp, with which you can adjust the depth of positive feedback, which allows you to quite accurately select the required mode of operation of the cascade. Coil L3 with adjustable inductance allows you to match the resistance of the output circuit with the input impedance of the antenna. This is important because A piece of wire of arbitrary length is often used as an antenna. Coil L2 is wound on a ceramic mandrel with a diameter of D-40mm and has 40 turns of PEL-0.7 wire (winding - turn to turn, taps are evenly distributed along the entire length of the winding), L4 - on a ceramic mandrel with a diameter of D-35mm and has 50 turns of wire PEL-0.6. In the author's version, coil L1 (choke) has an inductance of 1 µH, L2 - 8 µH, L3 - 250 µH, L4 -16 µH. I suggest winding L1 on a ceramic frame with a diameter of D-18mm and a length of 95mm with PELIA-0.35 wire (130 turns). The first 15 turns (closest to the anode) should be discharged in increments of 1.5 mm, the rest of the winding - turn to turn. I recommend making coil L3 similarly to L4, but increasing the number of turns to 100 and making taps from it (11 taps - according to the number of contacts in the switching strip) in order to make it possible to change the inductance of the coil. The taps should be positioned evenly along the length of the coils - this will simplify its design and, at the same time, allow it to maintain its tuning functions.
Tuning to the frequency in this circuit is done using capacitor C2, and the capacitance of capacitor C5 is selected according to the maximum signal at the output, i.e. adjust the output circuit L4-C5 to resonance. This design of the circuit allows you to tune the output circuit not only to the fundamental frequency, but also to its harmonics (most often the third is used). In this way, it is possible to increase the stability of the frequency of the signal generated by the generator, because The local oscillator operates at a frequency three times lower than the frequency of the output signal.
Figure 5 shows a hurdy-gurdy circuit made using two 6PCS radio tubes (you can also use 6P6S tubes, but there is no point in this - it is better to use one 6PCS). This circuit provides a more powerful output signal (about twice that of a single tube circuit). The anodes of the lamps are partially included in the generator circuit to reduce the effect of shunting. In the author’s version, it is recommended to wind coils L1-L3 on one ceramic frame with a diameter of D-40mm. Coil L1 contains 32 turns of PEL-0.3 wire, L2 - 41 turns of PEL-0.4 wire, L3 - 58 turns of PEL-0.7 wire. All coils are wound turn to turn. I recommend reducing the number of turns of each coil by 60 percent, otherwise the generation frequency will move from the mid-wave range to the long-wave range. By adjusting the resistance of resistor R1, you can change the operating mode of the radio tubes.
Figure 6 shows a diagram of a transmitter using two radio tubes. The oscillatory circuit L1-C2 is included in the cathode circuits of the lamps. Coils L1 and L2 are wound on one ceramic frame D-20 mm: And contains 60 turns of PEL-0.3 wire, L2 - 30 turns of PEL-0.4 (winding both coils - turn to turn). 2-3 turns of mounting wire (in insulation) are wound on top of coil L2, the ends of which are connected to an incandescent light bulb with a voltage of 6.3 V and a current of 0.28 mA (from a flashlight). This simplest chain provides an indication of the presence of RF generation. In addition, a neon light bulb placed close to the coil can be used as an RF indicator. By the intensity of the lamp's glow, one can judge the change in output power when tuning the range or a change in the parameters of the antenna (for example, when tuning it). So, if, when tuning the antenna, the frequency approaches the resonant one, then the light bulb will glow weaker (by the minimum glow one can judge that the antenna is tuned to resonance with the frequency generated by the transmitter, since there is a maximum power take-off). If the antenna breaks, the light bulb will glow as brightly as possible, and if there is a short circuit in the antenna, it may go out completely (this depends on the magnitude of the connection between the output circuit and the antenna, which is determined by the capacitance of the variable capacitor C1). The power switch SA1 also serves as a “receive/transmit” switch.
Figure 7 shows a diagram of the transmitting attachment on the GU50 radio tube. A significant difference between this circuit and the previous ones is the increased output power. Amplitude modulation is carried out along the protective grid of the lamp. Using a variable capacitor C5, the set-top box is tuned to the selected frequency, and using a capacitor C1, the output impedance of the transmitter is matched with the input impedance of the antenna. We should not forget that in this circuit one of the plates of the variable capacitor C5 is under a voltage of 800 V, so be very careful and use a control knob made of high-quality dielectric material to adjust the capacitance of this capacitor.
Coil L1 is wound on a ceramic frame D-40 mm and contains 50 turns of PEL-0.7 wire (winding - turn to turn) with a tap from the middle.
Figure 8 shows another diagram of a transmitter made on a GU50 radio tube. In it, the generation frequency is set by the L1-C2 circuit, and at the output of the device the so-called P-circuit C7-L2-C8 is used, which makes it possible to very well match the output impedance of the cascade with the input impedance of the antenna. Using the variable capacitor C7, the P-circuit is tuned to resonance (the output resistance of the lamp is matched with the resistance of the P-circuit), and using C8, the coupling value with the antenna is selected. Amplitude modulation of the output signal is carried out along the protective grid of the lamp.
Chain C3-VD1-R2 are elements for protecting speaker circuits from RF interference. By selecting the resistance of the resistors (within 0.5-1 MOhm) and R3, you can select the optimal mode of operation of the lamp.
Coil L1 is wound on a cylindrical ceramic frame D-40 mm with PEL wire 0.9 and contains 60 turns, wound turn to turn. Coil L2 is wound on a ceramic frame D-50 mm and contains 70 turns of PEL wire with a diameter of 1.2-1.5 mm (winding - turn to turn). Anode choke L3 is wound on a ceramic frame D-12 mm. The original recommendation states that it contains 7 sections of 120 turns of PEL-0.4 wire wound in bulk, but most likely two sections of 120 turns are sufficient.
V.Rubtsov, UN7BV
Astana, Kazakhstan
The transmitter consists of the following blocks: master oscillator; buffer stage; output stage; modulator.
Master oscillator.
The master oscillator is assembled according to a capacitive three-point circuit using a 6P44S lamp. The contour coil is wound on a frame with a diameter of 20 mm, with a wire of 0.8 mm diameter, 40 turns. To achieve frequency stabilization in the control grid, it is necessary to use KSO capacitors of group G + -5%.
Buffer cascade
The buffer stage is designed to decouple the master oscillator from subsequent stages, which contributes to the stability of the generation frequency. In the same cascade, amplitude modulation of the carrier frequency occurs. The modulator must be a tube modulator that provides 200 volts or more at the output of the modulation transformer. 
Output stage
The Dr1 inductor is wound with 0.23-0.35 mm wire on a ceramic frame with a diameter of 10-15 mm, four sections of 80 turns per pile. Choke Dr2 is wound with three 0.5 mm wires on a thick ferrite rod. The chokes in the filament circuit are also wound on ferrite rods with 1.0-1.5 mm wire. The chokes are wound until the rod is completely filled, leaving room for its attachment. The contour coil is wound on a frame with a diameter of 50 mm with a 2.0 mm wire, the number of turns is 35-38
Modulator for AM transmitter
The modulator is a 4-stage low frequency amplifier. The microphone amplifier is made on one half of the 6N2P. The microphone used is an electret (tablet). C1 limits it at high frequencies to avoid excitation. Resistances R1 and R2 determine the voltage on the microphone (affects sensitivity); it should be within 1.5...3.0 V (depending on the type of microphone). Capacitor C3 prevents high DC voltage from reaching subsequent stages. Next comes a two-stage voltage amplifier. The signal comes to it from resistance R4 “volume”. Resistor R9 is a volume control for the line input (tape recorder, CD player, computer, etc.), and it is also a tone control for the microphone input. The audio power amplifier is assembled on a 6P3S. The amplifier is loaded onto a transformer, which you can wind yourself, the data is shown in the diagram. The power transformer from old Record and Vesna TVs (TS-180) also works well. When connecting to a transmitter, you may need to change the polarity of the secondary winding connection.
Antenna
The transmitter was loaded onto an "American" type antenna. Antenna length 48m made of 1.6mm wire. The transmitter was connected with a 1.0mm wire. The reduction is connected at a distance of 1/3 of the entire length.
A simple circuit of an AM HF transmitter for the amateur 3 MHz band for a novice radio amateur: a detailed description of the operation and device
Proposed transmitter circuit does not contain scarce parts and is easily repeatable for beginning radio amateurs taking their first steps in this exciting, exciting hobby. The transmitter is assembled according to the classical design and has good characteristics. Many, or rather, all radio amateurs begin their journey with just such a transmitter.
It is advisable to start assembling our first radio station with a power supply, the diagram of which is shown in Figure 1:
picture 1:
The power supply transformer can be used from any old tube TV. The alternating voltage on winding II should be about 210 - 250 v, and on windings III and IV 6.3 v each. Since the load current of both the main rectifier and the additional one will flow through diode V1, it must have a maximum permissible rectified current twice as large as the other diodes.
Diodes can be taken of the modern type 10A05 (sample voltage 600V and current 10A) or, even better, with a voltage reserve - 10A10 (sample voltage 1000V, current 10A), when using more powerful lamps in the transmitter power amplifier, we need this reserve It can be useful.
Electrolytic capacitors C1 – 100 µF x 450V, C2, C3 – 30 µF x 1000V. If you don’t have capacitors with an operating voltage of 1000V in your arsenal, then you can make up 2 series-connected capacitors of 100 μF x 450V.
The power supply must be made in a separate housing, this will reduce the overall dimensions of the transmitter, as well as its weight, and in the future it will be possible to use it as a laboratory one, when assembling structures on lamps. Toggle switch S2 is installed on the front panel of the transmitter and is used to turn on the power when the power supply is under the table or on the far shelf, where you really don’t want to reach (can be excluded from the circuit).
Figure 2:
Modulator details:
C1 – 20mkfx300v, C7 – 20mkfx25v, R1 – 150k, R7 – 1.6k, V1 – D814A,
C2 – 120, C8 – 0.01, R2 – 33k, R8 – 1m variable, V2 – D226B,
C3 – 0.1, C9 – 50mkfh25v, R3 – 470k, R9 – 1m, V3 – D226B,
C4 – 100 µFx300V, C10 – 1 µF, R4 – 200k, R10 – 10k,
C5 – 4700, C11 – 470, R5 – 22k, R11 – 180,
C6 – 0.1, R6 – 100k, R12 – 100k – 1m
Electret microphone from a cassette recorder or telephone headset (tablet). The part of the circuit highlighted in red is necessary to power the microphone; if you intend to use only a dynamic microphone, then it can be removed from the design. Trimmer resistor R2 sets the voltage to + 3V. R8 – modulator volume control.
The output transformer is from a tube receiver or a TV of the TVZ type; you can also use vertical scan transformers TVK - 110LM2, for example.
The setting consists of measuring and, if necessary, adjusting the voltages at terminals (1) +60V, (6) +120V, (8) +1.5V of the 6N2P lamp and at terminals (3) +12V, (9) +190V 6P14P.
Figure 3:
Transmitter details.
C1 – 1 section gearbox 12x495, C10 – 0.01, R1 – 68k
C2 – 120, C11 – 2200, R2 – 120k
C3 – 1000, C12 – 6800, R3 – 5.1k
C4 – 1000, C13 – 0.01, R4 – 100k variable
C5 – 0.01, C14 – 0.01, R5 – 5.1k
C6 – 100, C15 – 0.01, R6 – 51
C7 – 0.01, C16 – 470 x 1000V, R7 – 220k variable
C8 – 4700, C17 – 12 x 495, R8 – 51
C9 – 0.01, R9 – 51
R10 – 51
The GPA coil L1 is wound on a frame with a diameter of 15 mm and contains 25 turns of 0.6 mm PEV wire. The inductor in the cathode of lamp L2 is factory-made and has an inductance of 460 μH. In my design, I used a choke from a TV, wound on an MLT - 0.5 resistor with a wire in a slot winding. Chokes L3 - L6 are wound between the cheeks on old-style VS-2 resistors and have 4 sections of 100 turns of PEL-2 wire with a diameter of 0.15 mm. Chokes L7 and L8 each have 4 turns of PEV wire with a diameter of 1 mm wound on top of resistors R8 and R9 MLT-2 with a resistance of 51 Ohms and serve to protect the final stage from self-excitation at high frequencies. The anode choke L9 is wound on a ceramic or fluoroplastic frame with a diameter of 15 - 18 mm and a length of 180 mm. PELSHO wire 0.35 turn to turn and has 200 turns, the last 30 turns in increments of 0.5 - 1 mm.
The L10 contour coil is wound on a ceramic, cardboard or wooden frame with a diameter of 50 mm and has 40 turns of PEL-2 wire with a diameter of 1 mm. When using a wooden frame, it should be well dried and varnished, otherwise, when exposed to high RF current, it will dry out, which will lead to deformation of the winding and possibly even a breakdown between the turns.
C17 is a double unit from a tube receiver with plates removed through one in a movable and fixed block.
Variable resistor R4 sets the bias on the control grid of the 6P15P lamp, and resistor R7 sets the bias for 6P36S lamps.
Relays can be of any type for a voltage of 12V with a gap between contacts of 1mm with a switching current of 5A.
Ammeter for current 100 mA,
The final stage is tuned to resonance using the minimum milliammeter readings.
The bias circuit is shown in Figure 4:
Figure 4:
Transformer T1, any step-down transformer 220v/12v with reverse connection. The secondary (step-down) winding is included in the filament circuit of the lamps, and the primary serves as a step-up winding. The output of the rectifier is about -120V and is used to set the bias of the lamps of the final stage of the transmitter.
Useful thing!
The figure above shows a diagram of the field strength indicator. This is a circuit of the simplest detector receiver, only instead of headphones, it has a microammeter, by which we can visually observe the signal level when tuning the transmitter to resonance.
