Dedicated to young radio amateurs...
A radio signal, once generated, is carried into the depths of the Universe at the speed of light... This phrase, read in the magazine “Young Technician” in my distant childhood, made a very strong impression on me and even then I firmly decided that I would definitely send my signal to our “brothers in mind” , no matter what it costs me. But the path from desire to dream come true is long and unpredictable...
When I first started getting into radio business, I really wanted to build a portable radio station. At that time I thought it consisted of a speaker, an antenna and a battery. All you have to do is connect them in the correct order and you will be able to talk with friends wherever they are... I filled more than one notebook with possible diagrams, added all kinds of light bulbs, coils and wiring. Today these memories only make me smile, but then it seemed to me that just a little more and I would have a miracle device in my hands...
I remember my first radio transmitter. In the 7th grade I went to a sports radio direction finding club (so-called fox hunting). On one of the beautiful spring days, our last “fox” gave orders to live long. The head of the circle, without thinking twice, handed it to me with the words - “... well, you fix it there...”. I was probably terribly proud and happy that I was entrusted with such an honorable mission, but my knowledge of electronics at that time did not reach the “candidate minimum.” I knew how to distinguish a transistor from a diode and had a rough idea of how they work separately, but how they work together was a mystery to me. Arriving home, I opened the small metal box with awe. Inside it was a board consisting of a multivibrator and an RF generator on a P416 transistor. For me this was the pinnacle of circuit design. The most mysterious detail in this device was the master oscillator coil (3.5 MHz), wound on an armored core. Childhood curiosity overpowered common sense and a sharp metal screwdriver dug into the armored casing of the coil. “Gripping,” there was a crunch and a piece of the armored coil body fell to the floor with a thud. While he was falling, my imagination had already painted a picture of me being shot by the leader of our circle...
This story had a happy ending, although it happened a month later. I finally repaired the “Fox”, although to be more precise, I made it anew. The beacon board, made of foil getinax, could not withstand torture with my 100-watt soldering iron, the tracks peeled off due to the constant resoldering of parts... I had to make the board again. Thanks to my dad for bringing (obtained from somewhere with great difficulty) foil getinax, and to my mom for the expensive French red nail polish that I used to paint the board. I couldn’t get a new armor core, but I managed to carefully glue the old one with BF glue... The repaired radio beacon joyfully sent out its weak “PEEP-PEEP” on the air, but for me it was comparable to the launch of the first artificial Earth satellite, which announced to humanity the beginning of space exploration. era with the same intermittent signal at frequencies of 20 and 40 MHz. Here's the story...
There are a huge number of generator circuits in the world capable of generating oscillations of various frequencies and powers. Typically, these are quite complex devices based on diodes, lamps, transistors or other active elements. Their assembly and configuration requires some experience and expensive equipment. And the higher the frequency and power of the generator, the more complex and expensive the devices are needed, the more experienced the radio amateur must be in this topic.
But today, I would like to talk about a fairly powerful RF generator, built on just one transistor. Moreover, this generator can operate at frequencies up to 2 GHz and higher and generate quite a lot of power - from units to tens of watts, depending on the type of transistor used. A distinctive feature of this generator is the use symmetrical dipole resonator, a kind of open oscillatory circuit with inductive and capacitive coupling. Don't be scared by this name - the resonator consists of two parallel metal strips located at a short distance from each other.
I conducted my first experiments with generators of this type back in the early 2000s, when powerful RF transistors became available to me. Since then, I have periodically returned to this topic, until in the middle of summer a topic arose on the website VRTP.ru on the use of a powerful single-transistor generator as a source of HF radiation to jam household appliances (music centers, radio tape recorders, televisions) by directing modulated HF -currents in the electronic circuits of these devices. The accumulated material formed the basis of this article.
The circuit of a powerful RF generator is quite simple and consists of two main blocks:
The “heart” of our generator is high frequency MOSFET transistor. This is a fairly expensive and rarely used element. It can be bought at a reasonable price in Chinese online stores or found in high-frequency radio equipment - high-frequency amplifiers/generators, namely, in cellular base station boards of various standards. For the most part, these transistors were developed specifically for these devices.
Such transistors are visually and structurally different from those familiar to many radio amateurs from childhood. KT315 or MP38 and are “bricks” with flat leads on a powerful metal substrate. They come in small and large sizes depending on the power output. Sometimes, in one package there are two transistors on the same substrate (source). Here's what they look like:
The ruler below will help you estimate their sizes. To create an oscillator, any MOSFET transistors can be used. I tried the following transistors in the generator: MRF284, MRF19125, MRF6522-70, MRF9085, BLF1820E, PTFA211801E- they all work. This is what these transistors look like inside:
In addition to the RF transistor and copper, you will need a microcircuit to make the generator 4093 - these are 4 2I-NOT elements with Schmitt triggers at the input. It can be replaced with a microcircuit 4011 (4 elements 2I-NOT) or its Russian equivalent - K561LA7. You can also use another generator for modulation, for example, assembled on timer 555. Or you can completely exclude the modulating part from the circuit and just get an RF generator.
A composite p-n-p transistor is used as a key element TIP126(you can use TIP125 or TIP127, they differ only in the maximum permissible voltage). According to the passport, it can withstand 5A, but it gets very hot. Therefore, a radiator is needed to cool it. Subsequently, I used P-channel field-effect transistors like IRF4095 or P80PF55.
The device can be assembled either on a printed circuit board or by surface mounting in compliance with the rules for RF mounting. The topology and type of my board are shown below: 
This board is designed for transistor type MRF19125 or PTFA211801E. For it, a hole is cut in the board corresponding to the size of the source (heat sink plate).
One of the important points in assembling the device is to ensure heat removal from the source of the transistor. I used various radiators to suit the size. For short-term experiments, such radiators are sufficient. For long-term operation, you need a radiator of a sufficiently large area or the use of a fan circuit.
Turning on the device without a radiator is fraught with rapid overheating of the transistor and failure of this expensive radio element.
For experiments, I made several generators with different transistors. I also made flange mounts for the stripline resonators so that they could be changed without constantly heating the transistor. The photographs below will help you understand the installation details.
Before starting the generator, you need to double-check that its connections are correct so that you don’t end up with a rather expensive pile of transistors labeled “Burnt.” 
It is advisable to carry out the first start-up with control of the current consumption. This current can be limited to a safe level by using a 2-10 Ohm resistor in the generator power circuit (collector or drain of the modulating transistor).
The operation of the generator can be checked with various devices: a search receiver, a scanner, a frequency meter, or simply an energy-saving lamp. HF radiation with a power of more than 3-5 W makes it glow.
HF currents easily heat some materials that come into contact with them, including biological tissues. So Be careful, you can get a thermal burn by touching exposed resonators(especially when generators operate on powerful transistors). Even a small generator based on the MRF284 transistor, with a power of only about 2 watts, easily burns the skin of your hands, as you can see in this video:
With some experience and sufficient generator power, at the end of the resonator, you can ignite the so-called. “torch” is a small plasma ball that will be powered by RF energy from the generator. To do this, simply bring a lit match to the tip of the resonator.
T.N. "torch" at the end of the resonator.
In addition, it is possible to ignite an RF discharge between the resonators. In some cases, the discharge resembles a tiny ball of lightning moving chaotically along the entire length of the resonator. You can see what it looks like below. The current consumption increases somewhat and many terrestrial television channels “go out” throughout the house))).
In addition, our generator can be used to study the effects of RF radiation on various devices, household audio and radio equipment in order to study their noise immunity. And of course, with the help of this generator you can send a signal into space, but that’s another story...
P.S. This RF self-oscillator should not be confused with various EMP-jammers. High voltage pulses are generated there, and our device generates high frequency radiation.
High-frequency generators are used to generate electric current oscillations in the frequency range from several tens of kilohertz to hundreds of megahertz. Such devices are created using LC oscillation circuits or quartz resonators, which are elements for setting the frequency. The work patterns remain the same. In some circuits the harmonic oscillation circuits are replaced.
The device for stopping the electric energy meter is used to power household electrical appliances. Its output voltage is 220 volts, power consumption is 1 kilowatt. If the device uses components with more powerful characteristics, then more powerful devices can be powered from it.
Such a device is plugged into a household outlet and supplies power to the consumer load. The electrical wiring diagram is not subject to any changes. There is no need to connect the grounding system. The meter works, but takes into account approximately 25% of the network energy.
The action of the stopping device is to connect the load not to the mains supply, but to the capacitor. The charge of this capacitor coincides with the sinusoid of the network voltage. Charging occurs in high-frequency pulses. The current consumed by consumers from the network consists of high-frequency pulses.
Meters (electronic) have a converter that is not sensitive to high frequencies. Therefore, the energy consumption of the pulse type is taken into account by the meter with a negative error.
The main components of the device: rectifier, capacitance, transistor. The capacitor is connected in a series circuit with a rectifier, when the rectifier performs work on the transistor, it is charged at a given time to the size of the power line voltage.
Charging is carried out by frequency pulses of 2 kHz. At load and capacitance, the voltage is close to sine at 220 volts. To limit the current of the transistor during the period of charging the capacitance, a resistor is used, connected to the switch cascade in a series circuit.
The generator is made on logical elements. It produces 2 kHz pulses with an amplitude of 5 volts. The signal frequency of the generator is determined by the properties of elements C2-R7. Such properties can be used to configure the maximum error in energy consumption accounting. The pulse creator is made on transistors T2 and T3. It is designed to control the T1 key. The pulse creator is designed so that transistor T1 begins to saturate when open. Therefore, it consumes little power. Transistor T1 also closes.
The rectifier, transformer and other elements create the low-side power supply of the circuit. This power supply operates at 36 V for the generator chip.
First, check the power supply separately from the low voltage circuit. The unit must produce a current greater than 2 amperes and a voltage of 36 volts, 5 volts for a low power generator. Next, the generator is set up. To do this, turn off the power section. Pulses with a size of 5 volts and a frequency of 2 kilohertz should come from the generator. For tuning, select capacitors C2 and C3.
When tested, the pulse generator must produce a pulse current on the transistor of about 2 amperes, otherwise the transistor will fail. To check this condition, turn on the shunt with the power circuit turned off. The pulse voltage on the shunt is measured with an oscilloscope on a running generator. Based on the calculation, the current value is calculated.
Next, check the power part. Restore all circuits according to the diagram. The capacitor is turned off and a lamp is used instead of the load. When connecting the device, the voltage during normal operation of the device should be 120 volts. The oscilloscope shows the load voltage in pulses with a frequency determined by the generator. The pulses are modulated by the sine voltage of the network. At resistance R6 - rectified voltage pulses.
If the device is working properly, capacitance C1 is turned on, as a result the voltage increases. With a further increase in the size of the container C1 reaches 220 volts. During this process, you need to monitor the temperature of transistor T1. When heating up strongly at a low load, there is a danger that it has not entered saturation mode or has not completely closed. Then you need to configure the creation of impulses. In practice, such heating is not observed.
As a result, the load is connected at its nominal value, and the capacitance C1 is determined to be of such a value as to create a voltage of 220 volts for the load. Capacitance C1 is chosen carefully, starting with small values, because increasing the capacitance sharply increases the current of transistor T1. The amplitude of the current pulses is determined by connecting the oscilloscope to resistor R6 in a parallel circuit. The pulse current will not rise above what is allowed for a particular transistor. If necessary, the current is limited by increasing the resistance value of resistor R6. The optimal solution would be to choose the smallest capacitance size of capacitor C1.
With these radio components, the device is designed to consume 1 kilowatt. To increase power consumption, you need to use more powerful power elements of the transistor switch and rectifier.
When consumers are turned off, the device consumes considerable power, which is taken into account by the meter. Therefore, it is better to turn off this device when the load is off.
High frequency generators are made on a widely used circuit. The differences between the generators lie in the RC emitter circuit, which sets the current mode for the transistor. To generate feedback in the generator circuit, a terminal output is created from the inductive coil. RF generators are unstable due to the influence of the transistor on the oscillations. The properties of the transistor can change due to temperature fluctuations and potential differences. Therefore, the resulting frequency does not remain constant, but “floats”.
To prevent the transistor from affecting the frequency, it is necessary to reduce the connection of the oscillation circuit with the transistor to a minimum. To do this, you need to reduce the size of the containers. The frequency is affected by changes in load resistance. Therefore, you need to connect a repeater between the load and the generator. To connect voltage to the generator, permanent power supplies with small voltage pulses are used.
Generators made according to the circuit shown above have maximum characteristics and are assembled on. In many oscillator circuits, the RF output signal is taken from the oscillating circuit through a small capacitor, as well as from the electrodes of the transistor. Here it is necessary to take into account that the auxiliary load of the oscillation circuit changes its properties and frequency of operation. This property is often used to measure various physical quantities and to check technological parameters.
This diagram shows a modified high frequency oscillator. The feedback value and the best excitation conditions are selected using capacitance elements.
Of the total number of generator circuits, variants with shock excitation stand out. They operate by exciting the oscillation circuit with a strong impulse. As a result of the electronic impact, damped oscillations along a sinusoidal amplitude are formed in the circuit. This attenuation occurs due to losses in the harmonic oscillation circuit. The speed of such oscillations is calculated by the quality factor of the circuit.
The RF output signal will be stable if the pulses have a high frequency. This type of generator is the oldest of all those considered.
To obtain plasma with certain parameters, it is necessary to bring the required value to the power discharge. For plasma emitters, the operation of which is based on a high-frequency discharge, a power supply circuit is used. The diagram is shown in the figure.
On lamps, converts electrical direct current energy into alternating current. The main element of the generator's operation was an electron tube. In our scheme these are GU-92A tetrodes. This device is an electron tube with four electrodes: anode, shielding grid, control grid, cathode.
The control grid, which receives a low-amplitude high-frequency signal, closes some of the electrons when the signal is characterized by a negative amplitude, and increases the current at the anode when the signal is positive. The shielding grid creates a focus of the electron flow, increases the gain of the lamp, and reduces the capacitance of the passage between the control grid and the anode in comparison with the 3-electrode system by hundreds of times. This reduces the output frequency distortion of the tube when operating at high frequencies.
There is an RF transformer between the antenna and the generator output. It is designed to transfer power to the emitter from the generator. The antenna circuit load is not equal to the maximum power taken from the generator. Efficiency of power transfer from the amplifier output stage to the antenna can be achieved by matching. The matching element is a capacitive divider in the anode circuit circuit.
A transformer can act as a matching element. Its presence is necessary in various matching circuits, because without a transformer high-voltage isolation cannot be achieved.
Write comments, additions to the article, maybe I missed something. Take a look at, I will be glad if you find anything else useful on mine.
The proposed high-frequency generators are designed to produce electrical oscillations in the frequency range from tens of kHz to tens and even hundreds of MHz. Such generators, as a rule, are made using LC oscillatory circuits or quartz resonators, which are frequency-setting elements. Fundamentally, this does not change the circuits significantly, so high-frequency LC generators will be discussed below. Note that, if necessary, oscillatory circuits in some generator circuits (see, for example, Fig. 12.4, 12.5) can be easily replaced with quartz resonators.
High-frequency generators (Fig. 12.1, 12.2) are made according to the traditional “inductive three-point” circuit, which has proven itself in practice. They differ in the presence of an RC emitter circuit, which sets the operating mode of the transistor (Fig. 12.2) for direct current. To create feedback in the generator, a tap is made from the inductor (Fig. 12.1, 12.2) (usually from 1/3... 1/5 of its part, counting from the grounded terminal). The instability of high-frequency generators using bipolar transistors is due to the noticeable shunting effect of the transistor itself on the oscillatory circuit. When the temperature and/or supply voltage changes, the properties of the transistor change noticeably, so the generation frequency “floats”. To weaken the influence of the transistor on the operating frequency of generation, the connection of the oscillatory circuit with the transistor should be weakened as much as possible, reducing the transition capacitances to a minimum. In addition, the generation frequency is noticeably affected by changes in load resistance. Therefore, it is extremely necessary to include an emitter (source) follower between the generator and the load resistance.
To power generators, stable power sources with low voltage ripples should be used.
Generators made using field-effect transistors (Fig. 12.3) have the best characteristics.
High-frequency generators assembled using a “capacitive three-point” circuit using bipolar and field-effect transistors are shown in Fig. 12.4 and 12.5. Fundamentally, in terms of their characteristics, the “inductive” and “capacitive” three-point circuits do not differ, however, in the “capacitive three-point” circuit there is no need to make an extra terminal at the inductor.
In many generator circuits (Fig. 12.1 - 12.5 and other circuits), the output signal can be taken directly from the oscillatory circuit through a small capacitor or through a matching inductive coupling coil, as well as from electrodes of the active element (transistor) that are not grounded by alternating current. It should be taken into account that the additional load of the oscillatory circuit changes its characteristics and operating frequency. Sometimes this property is used “for good” - for the purposes of measuring various physical and chemical quantities and monitoring technological parameters.
In Fig. Figure 12.6 shows a diagram of a slightly modified version of the RF generator - a “capacitive three-point”. The depth of positive feedback and optimal conditions for exciting the generator are selected using capacitive circuit elements.
The generator circuit shown in Fig. 12.7, is operational in a wide range of inductance values of the oscillating circuit coil (from 200 μH to 2 H) [R 7/90-68]. Such a generator can be used as a wide-range high-frequency signal generator or as a measuring converter of electrical and non-electrical quantities into frequency, as well as in an inductance measuring circuit.
Generators based on active elements with an N-shaped current-voltage characteristic (tunnel diodes, lambda diodes and their analogues) usually contain a current source, an active element and a frequency-setting element (LC circuit) with parallel or series connection. In Fig. Figure 12.8 shows a circuit of an RF generator based on an element with a lambda-shaped current-voltage characteristic. Its frequency is controlled by changing the dynamic capacitance of the transistors when the current flowing through them changes.
The NI LED stabilizes the operating point and indicates the generator is on.
A generator based on an analogue of a lambda diode, made on field-effect transistors, and with stabilization of the operating point by an analogue of a zener diode - an LED, is shown in Fig. 12.9. The device operates up to a frequency of 1 MHz and higher when using the transistors indicated in the diagram.
In Fig. 12.10, in order of comparing the circuits according to their degree of complexity, a practical circuit of an RF generator based on a tunnel diode is given. A forward-biased junction of a high-frequency germanium diode is used as a semiconductor low-voltage voltage stabilizer. This generator is potentially capable of operating at the highest frequencies - up to several GHz.
High-frequency frequency generator, the circuit is very reminiscent of Fig. 12.7, but made using a field-effect transistor, is shown in Fig. 12.11 [Rl 7/97-34].
The prototype RC oscillator shown in Fig. 11.18 is the generator circuit in Fig. 12.12.
This generator is distinguished by high frequency stability and the ability to operate in a wide range of changes in the parameters of frequency-setting elements. To reduce the influence of the load on the operating frequency of the generator, an additional stage is introduced into the circuit - an emitter follower made on a bipolar transistor VT3. The generator is capable of operating at frequencies above 150 MHz.
Among the various generator circuits, it is especially worth highlighting generators with shock excitation. Their work is based on periodic excitation of an oscillatory circuit (or other resonating element) with a powerful short current pulse. As a result of the “electronic impact”, periodic sinusoidal oscillations of a sinusoidal shape appear in the oscillatory circuit excited in this way. The damping of oscillations in amplitude is due to irreversible energy losses in the oscillatory circuit. The rate at which oscillations decay is determined by the quality factor (quality) of the oscillatory circuit. The output high-frequency signal will be stable in amplitude if the excitation pulses follow at a high frequency. This type of generator is the most ancient among those under consideration and has been known since the 19th century.
A practical circuit of a generator of high-frequency shock excitation oscillations is shown in Fig. 12.13 [R 9/76-52; 3/77-53]. Shock excitation pulses are supplied to the oscillatory circuit L1C1 through the diode VD1 from a low-frequency generator, for example, a multivibrator, or another square-wave generator (RPU), discussed earlier in Chapters 7 and 8. The great advantage of shock excitation generators is that they operate using oscillatory circuits of almost any type and any resonant frequency.
Another type of generators is noise generators, the circuits of which are shown in Fig. 12.14 and 12.15.
Such generators are widely used to configure various radio-electronic circuits. The signals generated by such devices occupy an extremely wide frequency band - from a few Hz to hundreds of MHz. To generate noise, reverse-biased junctions of semiconductor devices operating under the boundary conditions of avalanche breakdown are used. For this, transitions of transistors (Fig. 12.14) [Rl 2/98-37] or zener diodes (Fig. 12.15) [Rl 1/69-37] can be used. To configure the mode in which the generated noise voltage is maximum, the operating current through the active element is adjusted (Fig. 12.15).
Note that to generate noise, you can also use resistors combined with multistage low-frequency amplifiers, super-regenerative receivers, and other elements. To obtain the maximum amplitude of the noise voltage, it is usually necessary to individually select the most noisy element.
In order to create narrowband noise generators, an LC or RC filter can be included at the output of the generator circuit.
Literature: Shustov M.A. Practical circuit design (Book 1), 2003
