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1 Making a transmitter for 2.8 3.3 MHz with amplitude modulation to the safety net. To drive three GU 50 lamps into the control grid, you need from 50 to 100V RF voltage, with a power of not more than 1 W. And for the buildup "to the cathode" - already tens of watts. It was necessary to decide on the "exciter" scheme. The prototype of the "causative agent" was made according to the scheme cx.1. He gave out "honest" 10W without much effort. But this power is clearly in excess, for the buildup of three GU 50 lamps into the control grid. When the supply voltage drops to 12V, the power drops to 5W. In the course of the experiment, the generator was also tested according to the scheme cx.2,3. On the emitter of the generator transistor in this embodiment, the voltage diagram was somewhat more beautiful, but this did not affect the final result in any way.
2 I give stress diagrams at point A. Diagram "a" refers to cx.1. Diagram "b" and "c" refers to cx.2. Diagram "b" was obtained by reducing C5 to 180Pf. It was decided to make the "EXCITOR" according to cx.3. Transistors can be used for any high-frequency low and medium power. tr1 and tr2 are wound on ferrite rings with an outer diameter of 10-12 mm with a permeability of 1000 or more. The windings contain turns of self-made twisted "triple" and "five". The manufacture of transformers is usual, with a twisted (slightly, 1 turn per cm) bundle of PEL wire, we wind turn to turn, evenly distributing the winding around the circumference of the ring. Then in Tr1 primary winding we make of two “lines” connected in series, the secondary is single, in Tr2 the primary is single, and the secondary winding is made of four (for a purely AM transmitter from two to three) serial “lines”. On the secondary winding (when all four lines are turned on) of the output stage, an RF voltage amplitude of up to 120V develops (the varnish insulation of the wires must be “correct”) at a load of 820Ω at a current consumption of a local oscillator of 1A. There is obviously a lot of such power. Therefore, it is necessary to tune the output stage to a load of approximately 2.7..3K. By adjusting the current consumption of T3 by the resistor R8, it is necessary to obtain the amplitude of the output voltage V. In this case, the resistance of the resistor R8 was 1 1.3K. With a supply voltage of the circuit from 9 to 12V, the TOTAL current consumption turned out to be 150-
3 250mA. The voltage waveforms on the load are given below. In the final version, the elements numbered R8, D4, C12 (cx.2) were removed, and the beginning of the secondary winding TP1 was connected to MACE.
4 It can be seen from them that the lamps are quite possible to “start” both in class “B” for an AM transmitter (two (three) serial lines are used in Tr2 in the secondary winding) and in class “C” (all four serial lines are used in Tr2 in the secondary winding). Due to the fact that the output stage provides an excess of power, it was tempting to use only the pre-terminal stage on T2 with a Tr2 transformer. But more than 20V amplitude at a 2K load could not be obtained. Those who are not satisfied with the signal shape from the generator driver should make an “exciter” according to the scheme where the second and third stages operate in an economical class C, and there is a sinusoid at the output, but the amplitude is already less than thirty percent. In the end, I applied it so as not to force the lamp modes. Power supply The power supply of the transmitter is without features, made on the transformer TS-270. It is mounted on the chassis through shock-absorbing rubber washers. Chokes are used from old tube TVs. Diodes in rectifiers are any rectifiers, for current 1 3A and reverse voltage from 600V. All of them must be shunted with capacitors. The output stage of the transmitter. The output stage of the transmitter is built on three GU50 lamps operating in class "B" and one 6P15P as a modulator with an inductive load. The limiter can not be “unsoldered” if there is no habit of screaming very loudly into the microphone, or you can adjust it to suit your speech characteristics by adding one more - two cells of anti-parallel diodes (any low-power, rectifying ones). Modulation is carried out on a protective grid GU50. There are no features in such a circuit solution, therefore, a detailed explanatory text is not required. It can also be added that the anode choke can have any design, as long as the inductance is at least 1200 μH, this is due to the fact that the π circuit is designed for a high-resistance load, approximately 4.6K, since it is supposed to “power” the antenna in “half-wave” in one of its ends (beginnings). Grid choke not less than 500 μH. The whole "garden", with fixed biases, chokes, was made on the assumption that the quiescent current would be set for each lamp separately, but in practice it turned out that this did not give much. Therefore, a fixed negative offset may or may not be
5 to do, but combine all control grids and ground them through a 30K..40K auto-bias resistor. The π loop data is calculated independently, depending on the frequency range and the antenna used. (The equivalent output impedance of one GU50 lamp is 4600 ohms. Three, respectively, 1533 ohms).
6 Transmitter automation Switching the transmitter to the "RECEPTION" mode occurs simultaneously by removing the excitation, that is, turning off the power supply of the local oscillator and de-energizing the power supply rectifiers of the transmitter's power section. Microphone amplifier The microphone amplifier-compressor is made on a microcircuit “torn out” from a DVD set-top box (from a “karaoke” microphone path) and two transistors. He "gives out" to the grid 6P15P "put"
7 2..2.5V LF amplitude. For lovers of modulation “in the foreground”, the amplitude level can be raised to 5V with a tuning resistor R10. Also in the microphone housing there is a control button through which voltage is supplied to the power supply circuit of the transmitter control relay. This button is also duplicated by the toggle switch "pr.-per." on the front of the transmitter. I used both electret and dynamic microphones, they work well, of course, each with its own frequency spectrum. Another MU option with a dynamic microphone. and my most "favorite" MU option: The design of the transmitter must comply with the usual requirements for the layout and installation of high-power RF devices. The circuit design of the transmitter has the right to its own life, but the practice of implementing it
8 showed that it is much easier and clearer to build such a transmitter entirely on tubes, well, maybe with the exception of a microphone amplifier. Then the power supply will be simpler and there will be less ambiguity in understanding the tuning process. I would also like to note that the modulation method “to the protective grid” is good, the correspondents note “a clean, neat signal”, but in terms of “assertiveness” and “arrogance” it is still inferior to the proven modulation to the screen grid through a cathode follower. The simplicity of the solution is to “power” a high-impedance antenna directly from the output of the pi circuit, which is fraught with unpredictable “HF pickups” on low signal paths of the transmitter. Therefore, if you want such "simplicity", then you need to take care of the normal shielding of the low signal path of the transmitter and the elimination of ways to form a multiplicative background. This is due to the fact that the antenna has a very high input impedance, and the output stage, trying to “push” the “HF power” out of itself, pushes it anywhere, and not only into the antenna. Any design that has a small capacitive (5-10pF) connection with the Pi circuit and the initial section of the antenna fabric already successfully takes on almost a quarter of the output power of the transmitter. And if RF pickup gets, for example, in the circuits of diode rectifiers not shunted by capacitors, then the diodes will work as mixers of the RF signal frequency and the AC frequency. mains voltage. From the foregoing, we can conclude that it is more correct to “connect” “half-wave” antennas to the Pi circuit of the transmitter through a low-resistance feeder, “powering” them at the corresponding points of the antenna sheet.
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The transmitter of the second category is intended for conducting half-duplex telegraph communication on the bands 10, 20, 40, 80 m and simplex telephone communication on 10 and 80 m bands. The power input 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, buffer-multiplier, amplifier-doubler, final amplifier), modulator and rectifiers.
The master oscillator assembled on the L3 lamp operates in the range of 80 m. To increase the frequency stability, the screen grid voltage is stabilized using the L2 zener diode, and in oscillatory circuit generator included capacitors C20, C24 and C27 with different temperature coefficients. Setting the frequency of the master oscillator is carried out by the first section of the dual variable capacitor C21a.
The transmitter is manipulated along the control grid circuit of the master oscillator lamp: when the key is pressed, a blocking voltage of 75 V is applied to the lamp grid through resistors R26, L25. When the key is pressed, 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 choke Dr2 through the transition capacitor C38, this stage is made on an L4 lamp and operates in the buffer-amplifier mode when operating on the 40 and 80 m bands and in the multiplier buffer mode when operating on the 20 and 10 m bands. In the first case, the Dr4 inductor is connected by relay contacts P1 / 1 to the anode of the lamp in series with the L2C34C35 circuit. On the ranges of 40 and 80 m, the circuit turns out to be detuned, and the role of the input load is performed by the throttle. When operating on the ranges of 20 and 10 m, relay P1 switches the choke Dr4 into the circuit for decoupling the anode power supply of the lamp. 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 tuned by capacitor C21b (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 range, a separate circuit is connected to the anode of the lamp using the P3 switch: on the range of 80 m - the L3С42 circuit, while the lamp operates in the oscillation amplification mode; on the range of 40 m - circuit С4С43 the lamp operates in doubling mode; on a range of 20 m - circuit L5C44, the lamp operates in amplification mode; on a range of 10 m - circuit L6C45, the lamp operates in doubling mode. With the help of 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 bands.
From the anode of the lamp L5, the excitation voltage through the capacitor C48 is supplied to the grid of the lamp L6 of the output amplifier, which operates in the power amplification mode on all ranges. The anode load of this stage is a P-circuit, consisting of coils L7 L5 and capacitors C55, C57. The coils are switched when switching 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 work in half duplex. A stabilized bias voltage is supplied to the control grid of the lamp L6 through the choke Dr7 from the gas-discharge stabilizer L1.
The modulator is assembled on transistors T1, T2 and lamp L7. It is designed to work with a dynamic microphone. The sensitivity of the modulator is not worse than 2 mV with an uneven frequency response in the frequency band of 300-3,000 Hz + 3 dB. Above frequency 3000 Hz frequency response modulator falls sharply, which provides a narrow band of radiation. The modulation depth is regulated by a variable resistor R34, on the axis of which the modulator switch Vk2 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 set up and control the transmitter operation mode, 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 made with one handle - switch P3, with the help of which all the necessary switching of the relay and circuits of the pre-terminal cascade is carried out.
To avoid radiation while tuning the transmitter to the frequency of the correspondent, 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 rectifiers connected in series, assembled on diodes D1-D16. The C2R9C3 filter is included in the 600 V voltage circuit. To power the anode and screen circuits of the remaining lamps, a rectifier on diodes D9-D16 with a filter C4, Dr1, C5 is used. A half-wave rectifier on a D17 diode with a filter C6, R21, C7 serves to obtain a bias voltage. Rectifier - 24 V on diodes D18-D21 with filter capacitor C8 is used to power the modulator and relay.
Details. Power transformer Tr1, choke Dr1, loop coils and high-frequency transmitter chokes are homemade. The transformer is assembled on the Sh-25 core, the thickness of the package is 50 mm. Winding data are given in table. one.
| 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 |
Choke Dr1 is made on the Sh-15 core, package thickness -32 mm. It contains 1250 turns of PEV 0.38 wire.
The data of the loop coils and high-frequency chokes are given in Table. 2.
| Designation | frame | |||||
| Number of turns | The wire | material | diameter, mm | winding | inductance, mgn | |
| 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 2.9 | without frame | 20 | step 2 mm | 0.3 |
| L7 | 22 | » | » | 33 | step 1 mm | 5 |
| L8 | 7 | » | » | 35 | step 3 mm | 1,4 |
| DR2-DR8 | 200×4 | PELSHO 0.15 | textolite | 5 | station wagon | 3000 |
All fixed resistors are of the MLT type. You can apply other resistors of appropriate resistances and capacities. Capacitors C2-C9, C13, C15, C18 - electrolytic; C1 type KBGI, KBGM with an operating voltage of at least 400 V; C10, C14 C16 - type MBM; C11, C12, C19, C39, C41, C49, C51, type BM-2; C17, C23, C28, C37, C38, C48, C56 - type KSO (C23 - preferably group G; C20, C24, C27, C35, C36, C42, C42, C44, C47, C58 - type KT C24 blue, C27 - Red); C25, C30, C32, C33, C40, C50 - type K40P; C53, C54 - SGM type; C22, C34 - type KPK-1; C21, C57 - standard twin units of any type, in C57 the fixed plates of both sections are connected in parallel; С46 - any type, this design uses KPV-140 with an extended axle; 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-gallet type 4P4N. Relay P1 - 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.
A vernier should be installed on the axis of the C21 capacitor unit. Scale - any type. In the described design, it is made on organic glass and is illuminated from behind (JI8 and L9 lamps). A pointer is fixed 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 of 400X230X65 mm. The front panel with dimensions 400 X X 170X2 mm is fastened to the chassis with bolts and brackets. This makes it possible to install the transmitter in any position, which is convenient for assembly and installation. Cascades are separated by partitions. Chassis, front panel and partitions are made of duralumin. The transmitter is placed in a detachable casing with holes for heat dissipation.
Rectifier elements, as well as resistors R18-R24, R40, R42, R44, R49, R50, R53 are mounted on two printed circuit boards, each pz of which is mounted on a power transformer (bottom and top). Most of the modulator elements are also mounted on a printed circuit board.
2nd category transmitter setup
The transmitter tuning methods 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, you should adjust the master oscillator using the GIR or a precisely calibrated receiver. At the same time, switch P2 should be in the "setting" position, P1- in the position Telf.
The required frequency range of the master oscillator is set roughly by selecting the capacitance of the capacitor C20 and exactly C22. Then, by adjusting the capacitance of the capacitor C34 and bending the plates of section C21b, the L2C34C35 circuit is adjusted.
The third stage is tuned according to the maximum reading of the IP1 device, included in the grid circuit of the L6 lamp with frequency control but to the receiver or GIR. It is necessary to make sure that each circuit is tuned with capacitor C46 at the beginning, middle and end of its operating range. In this case, the readings of the device 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 the antenna (a resistor with a resistance equal to the wave impedance of the feeder and a power of at least 30 watts, or an incandescent lamp). When switching to the telephone mode, the anode current should fall by half compared to the telegraph mode.
Class D tube modulator: allows you to increase the efficiency of the radio transmitter in AM mode up to 85-90%.A tetrode is used as a key element. The tetrode requires less power in the control grid circuit for excitation than the triode.
During operation: a significant part of the switching frequency period of the tetrode is in saturation, while the residual voltage on the anode is small, therefore, the screening grid current increases sharply. To eliminate the disadvantage, the mode is selected: so that the power loss on the screening grid does not exceed allowable level.
To the anode L1, through the Diode (D2) is connected Udop. constant voltage source. It fixes the residual U anode in the open state, and reduces the current of the screening grid, reduces static losses on the screening grid L1 (not associated with switching processes). The power loss on the screening grid is limited and will not exceed the allowable level, since i the current of the screening grid cannot increase more than the value determined by the voltage Uadm., and the power losses on the anode will be several times less than the allowable one.
The voltage value Udop should be chosen based on the allowable level of losses in the screen grid circuit while maintaining a sufficiently high efficiency. The calculation shows that nice results can be obtained by choosing Uadd ≈0.1 Еа. In this case, the output power of a radio transmitter with a class D modulator almost doubles, while reducing the efficiency of the modulator: by -10%.
Fig.1
The modulating signal Uin is fed to the input of the PWM signal shaper, which generates voltage pulses on the control grid, the duration of which is proportional to the value of the modulating signal. Accordingly, the voltage at the anode L1 also has the form of PWM pulses. The component of this voltage, which varies in accordance with the modulating signal, is separated by a low-frequency filter consisting of (Dp and C). fig.1
The calculation shows the rated output power of the radio transmitter in a single-cycle class D modulator on the GU-81m tetrode with 200W. up to 600 W with a slight decrease in the efficiency of the modulator (from 95 to 85%). In this case, the power dissipated on the screening grid will not exceed the permissible level (0.4 kW), and the increasing power loss at the anode will be several times less than the permissible value (600W).
In order to increase the efficiency in push-pull anode modulators, instead of a class B amplifier, a class D modulator can be used.
Unlike a single-acting amplifier, a push-pull one operates with a pulse duty cycle equal to two (periods of initial oscillations), there is no voltage at the modulator output, since the total average value of these pulses is zero. Voltage, audio frequency Uzv.h (Fig. 3) from the PWM unit (Fig. 2) is converted into two sequences of width-modulated pulses G1 and G2 of opposite polarity with a duty cycle of the pulses equal to two initial regenerations of the oscillations (Fig. 3), they arrive at lamps L1 and L2 working in key mode.
Encoded audio pulses from the PWM modulator are fed to the input of the 6N137 optocoupler. At the output of 6N137: the signal is inverted. Therefore, two additional buffer inverting elements D1.1 and D1.3 are used. - (D1-74HC14) inverting Schmitt triggers. (Fig. 4) Inverting the signal for the lower key is performed by inverter D1.2. The control signals of the upper and lower keys are sent to the dead-time formation nodes. They are made on logical elements"And" D2.1 and D2.2. - (D2-74HC08) . As a result, only the leading edges of the incoming pulses are delayed. The value of delays and, consequently, dead-time is determined by the products of R3*C3 and R4*C4 and can be adjusted to the parameters of the power module. Further processing of the control signals of the upper and lower keys occurs in different ways:
The lower key signal is amplified on the MAX4420 chip and fed to the driver output.
High key signal - amplified on the MAX4420 chip and has a "floating" potential of the common wire. Therefore, it is necessary galvanic isolation. In this case, transformer isolation with DC correction is used.
For a frequency range of 100-300 kHz and a duty cycle of 0 to 0.5, this solution is quite satisfactory.
Transformer parameters: T1 (core M 2500 NMS 16*10*8) winding 2*13 vit. These values are focused on the frequency range of 100-300 kHz. If you need to work with more low frequencies, the number of turns must be increased. and at higher frequencies, the number of turns must be reduced. Mounting the half-bridge driver in Fig. 5
Rice. 5 layout option and driver design.
Fig.3
Figure 3 shows a diagram: an alternating component (audio frequency voltage) is supplied to the load through an isolating Cp and a constant component through a modulation choke Lg. L1 and L2 and passing currents ivD1 and ivD2 at the required time intervals In accordance with the direction of the current in the load and in the inductor, the positive half-cycle of the amplified voltage works only L1 and D2., And in the negative L2 and D1.
There is no voltage at the output of the modulator, since the total average value of these pulses is zero. Dependences of changes in the values of average currents through lamps and diodes, referred to the peak value. The dependence of the power given by the push-pull modulator to the output stage of the transmitter on the AM coefficient is the dependence and efficiency gain.
Anode modulators for broadcasting transmitters up to 500 kW are built according to the sloping principle. Designed by Marconi.
Improving the Efficiency of Powerful Radio Transmitting Devices / Ed. A. D. Artyma: Communication, 1987.
Foreign radio transmitting devices / Ed. G. A. Zeitlenka, A. E. Ryzhkova - M .: Radio and communication, 1989.
US patent N 4272737, class. H 03 F 3/217, 1981.
AM TRANSMITTER at 3 MHz
The transmitter consists of four stages. The author used almost all used parts soldered at different timesfrom different techniques, and for many years lying in boxes. The output power of the transmitter has not been measured, according to rough calculations it is about 5 watts +/-, but most likely a plus. The master oscillator is assembled according to the classical three-point scheme, and despite its simplicity, the frequency keeps stable. The buffer stage on VT2 is loaded on a broadband transformer, it was not a hunt to set the circuit, and then equalize the characteristic over the entire range, there are more brands and details superfluous , and here in one fell swoop, or rather one transformer. The buffer stage is the load of the modulator assembled on the VLF LM386 chip. The author took the modulator circuit from Japanese radio amateurs, tested it and was satisfied. Well, the most important part is the final stage. It is assembled on a transistor pulled out of some kind of Korean radio. The KT805BM, which was in the first version, did not justify the hopes, and was, with disgrace, dismantled from the transmitter. As a result of the operation, the design was not damaged, but the patriotic spirit of the author was tested. However, having inserted 2T921A into the design for verification, peace of mind was restored. Even more, there was pride in our defense industry. But it was decided to leave the "Korean" as the best option, and it is easier to attach it to the radiator. The operation mode of the cascade is set by resistor R12. Diode D4 serves to stabilize the quiescent current. It must be mounted on the radiator directly near the output transistor. On the Korean transistor, the author slipped the diode directly under the transistor, since there was a place there. It is advisable to coat the attachment point with heat-conducting paste.
Construction details: I installed a variable capacitor with an air dielectric from a tube receiver. You can put almost any KPI, the main thing is to cover the range of 2.8 - 3.2 MHz.
The master oscillator coil L1 has 80 turns of PEL wire - 0.32 with a tap from 20 turns. Coils L2; L3 are the same and have 20 turns of PEL wire - 0.6.
All coils are wound on frames with a diameter of 12 mm.
As frames, the author used a polystyrene frame from a spool of thread.
Tr1 is wound on a ferrite ring with a diameter of 10 mm and a height of 5 mm. Twenty turns of folded and slightly twisted PELSHO wire - 0.25. Winding is carried out evenly over the entire ring.
Tr2 is wound on the same ring and contains 18 turns of PEL wire folded in three - 0.32.
L4 - 30 turns PELSHO - 0.25 on the same ring as Tr 1; 2. For L4, you can use a ring with smaller dimensions.
ATTENTION:
Before proceeding with the setup, it is necessary to connect the output of the transmitter to a load of 50 - 75 Ohm. The author had two connected parallel 100 ohm resistor, 2 W each.
SETUP:
The setup begins with a power check, having previously installed variable resistor R12 to the position of maximum resistance. By connecting an ammeter (multimeter) set to the maximum between the circuit and the power source, usually 10 A, power is supplied. If the readings have not changed much, then you can proceed to the actual setting. Turn off the Tr1 pin that goes to C24 so that power from the modulator does not go to the cascade. Connect a milliammeter between the +24 power supply and the right terminal of the Tr2 transformer. We connect the power, and with the resistor R12 we set the quiescent current of the output stage to about 30 mA. Then we restore all connections, control the signal with a frequency meter or receiver for the presence of generation. Then we set the middle of the range and with capacitors C19 - C21 we set the output filter to the maximum of the indicator readings. We connect the antenna, adjust C21 again and the setup is complete.
master generator.
To achieve frequency stabilization in the control grid, it is necessary to use KSO capacitors of the G + -5% group. The circuit is wound on a frame with a diameter of 20 mm, a wire with a diameter of 0.8 mm 40 turns.
Buffer stage
Everything is clear from the diagram. It can be simplified by removing Dr2 and everything else that goes with it. Put one resistance 27k from the control grid to ground. You can also apply modulation one output of the transformer immediately to the 3rd leg, and remove everything else to ground. The modulator must be a tube modulator 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 a wire of 0.23-0.35 mm on a ceramic frame with a diameter of 10-15 mm, four sections of 80 turns in bulk. Dr2 is wound with three wires on a thick ferite rod (from any receiver where there is a magnetic antenna) incandescent wire 1.0-1.5mm cathode 0.5mm. It is wound up to full filling leaving a place for its fastening. The circuit is wound on a frame with a diameter of 50 mm with a wire of 2.0 mm 35-38 turns. For a more complete calculation of the P-contour, you can use the program: click here 
Antenna
Antenna used with this transmitter "American" web length 48m wire 1.6mm reduction 12m wire 1.0mm. The reduction is connected at a distance of 1/3 from the hot end. 
But you can use any other antenna you like!