High frequency generator circuits. High-frequency generator: overview, features, types and characteristics

Radio Mir 2008 No. 9

The proposed RF generator is an attempt to replace the bulky industrial G4-18A with a smaller and more reliable device. Usually, when repairing and setting up HF equipment, it is necessary to “lay” HF bands using LC circuits, check the signal passage along the RF and IF paths, adjust individual circuits to resonance, etc. Sensitivity, selectivity, dynamic range and other important parameters of HF devices are determined by circuit design solutions, so it is not necessary for a home laboratory to have a multifunctional and expensive RF generator. If the generator has a fairly stable frequency with a “pure sine wave”, then it is suitable for a radio amateur. Of course, we believe that the laboratory’s arsenal also includes a frequency meter, an RF voltmeter and a tester. Unfortunately, most of the HF HF generator circuits I tried produced a very distorted sine wave, which could not be improved without unnecessarily complicating the circuit. The HF generator, assembled according to the circuit shown in Fig. 1, proved to be very good (the result was an almost pure sine wave throughout the entire HF range). The diagram is taken as a basis from. In my circuit, instead of adjusting the circuits with a varicap, a KPI is used, and the indicator part of the circuit is not used.

Fig.1 RF generator circuit

This design uses a variable capacitor type KPV-150 and a small-sized PM range switch (11P1N). With this KPI (10...150 pF) and inductors L2...L5, the HF range of 1.7...30 MHz is covered. As work on the design progressed, three more circuits (L1, L6 and L7) were added to the upper and lower sections of the range. In experiments with KPIs with a capacitance of up to 250 pF, the entire HF range was covered by three circuits. The RF generator is assembled on a printed circuit board made of foil-coated fiberglass laminate with a thickness of 2 mm and dimensions of 50x80 mm (Fig. 2). The tracks and mounting spots are cut out with a knife and a cutter. The foil around the parts is not removed, but is used instead of “ground”. In the figure of the printed circuit board, for clarity, these sections of the foil are not shown. Of course, you can also make the printed circuit board shown in.


Fig.2 Pay

The entire structure of the generator, together with the power supply (a separate board with a 9 V voltage stabilizer according to any circuit) is placed on an aluminum chassis and placed in a metal case of suitable dimensions. I used a cassette from an old equipment with dimensions of 130x150x90 mm. The front panel displays a range switch knob, a KPI adjustment knob, a small-sized RF connector (50 Ohm) and an LED indicator for powering on. If necessary, you can install an output level regulator (variable resistor with a resistance of 430...510 Ohms) and an attenuator with an additional connector, as well as a graduated scale. Unified sectional frames of the MF and DV ranges from obsolete radio receivers were used as the frames of the circuit coils. The number of turns of each coil depends on the capacity of the KPI used and is initially taken “with a reserve”. When setting up ("laying" the ranges) of the generator, some of the turns are unwound. Control is carried out using a frequency meter. Inductor L7 has a ferrite core M600-3 (NN) Ш2.8x14. Screens are not installed on circuit coils. The winding data of the coils, the boundaries of the subranges and the output levels of the RF generator are given in the table.

№№ Range, MHz Coil Number of turns Wire (diameter, mm) Frame, core Output level, V
1 80...30 L1 5 PEV-2 (1.0) Frameless with a diameter of 6 mm. L=12 mm 0,4...0,6
2 31...16 L2 12 PEV-2 (0.6) Ceramic diameter 6 mm, L=12 mm 1,1...1,2
3 18...8 L3 3x15 PEL (0.22) Unified
3-section
1,5...1,6
4 8,1...3,6 L4 3x35 PEL (0.22) -=- 1,7...1,9
5 3,8...1,7 L5 3x55 PEL (0.22) -=- 1,9...2,0
6 1,75...0,75 L6 3x75 PEL (0.22) -=- 1,8...2,2
7 1,1...0,46 L7 4x90 PEL (0.15) Unified
4-section
1,7...2,2

In the generator circuit, in addition to the indicated transistors, you can use field-effect ones KP303E(G), KP307 and bipolar RF transistors BF324, 25S9015, BC557, etc. It is advisable to use imported small-sized blocking containers. Coupling capacitor C5 with a capacity of 4.7...6.8 pF - type KM, KT, KA with low RF losses. It is very desirable to use high-quality ones (on ball bearings) as KPIs, but they are in short supply. Regulating KPIs of the KPV type with a maximum capacity of 80...150 pF are more accessible, but they break easily and have a noticeable “hysteresis” when rotating forward and backward. However, with rigid installation, high-quality parts and warming up the generator for 10...15 minutes, you can achieve a frequency “drop” of no more than 500 Hz per hour at frequencies of 20...30 MHz (at a stable room temperature). The signal shape and output level of the manufactured RF generator were checked using an S1-64A oscilloscope. At the final stage of setup, all inductors (except L1, which is soldered at one end to the body) are fixed with glue near the range switch and KPI.

Literature:
1. Shortwave GIR - Radio, 2006, No. 11, P. 72.

A. PERUTSKY, Bendery, Moldova.

Dedicated to young radio amateurs...

Preface

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 the 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...

Device diagram

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 should 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:

  1. Directly the HF self-oscillator itself on a transistor;
  2. A modulator is a device for periodically manipulating (launching) an RF generator with an audio (any other) frequency signal.

Details and design

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:


The second necessary material for the manufacture of this device is copper. You need two strips of this metal 1-1.5 cm wide. and 15-20 cm long (for a frequency of 400-500 MHz). Resonators can be made of any length, depending on the desired frequency of the generator. Approximately, it is equal to 1/4 wavelength.
I used copper, 0.4 and 1 mm thick. Less thin strips will not hold their shape well, but in principle they are also functional. Instead of copper, you can use brass. Resonators made of alpaca (a type of brass) also work successfully. In the simplest version, resonators can be made from two pieces of wire with a diameter of 0.8-1.5 mm.

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.

Assembling the device

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.


















































Starting the device

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))).

Device Application

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.

The proposed generator operates in the frequency range from 26560 kHz to 27620 kHz and is intended for tuning CB equipment. The signal voltage from "Output 1" is 0.05 V into a 50 Ohm load. There is also "Out.2". to which you can connect a frequency meter when setting up receivers. The generator provides the ability to obtain frequency-modulated oscillations. For this purpose, use “Input mod.”, to which a low-frequency signal is supplied from an external audio frequency generator. The generator is powered from a stabilized +12 V source. The current consumption does not exceed 20 mA. The master oscillator is made using field-effect transistors VT1. VT2. connected according to the "common source - common gate" circuit.

A generator assembled according to this design works well at frequencies from 1 to 100 MHz. because it uses field-effect transistors with a cutoff frequency >100 MHz. According to research conducted. this generator has short-term frequency instability (for 10 s) better than generators made using capacitive and inductive three-point circuits. The frequency drift of the generator for every 30 minutes of operation after a two-hour warm-up, as well as the levels of the second and third harmonics, are less than those of generators made according to the three-point circuit. Positive feedback in the generator is carried out by capacitor C10. The VT1 gate circuit includes an oscillatory circuit C5...C8. L1. determining the generation frequency of the circuit. Through a small capacitance C9, a varicap matrix VD1 is connected to the circuit. By applying a low-frequency signal to it, we change its capacitance and thereby carry out frequency modulation of the generator. The generator power supply is additionally stabilized by VD2. The high-frequency signal is removed from resistor R6. included in the source circuits of transistors. A broadband emitter follower on VT3 and VT4 is connected to the generator through capacitor C 11. The advantages of such a repeater are given in. A voltage divider (R14.R15) is connected to its output through capacitor C 15. The output resistance at "Output 1" is 50 Ohms. therefore, using a coaxial cable with a characteristic impedance of 50 ohms, a circuit with an input impedance of 50 ohms can be connected to it. for example an RF attenuator. published in [Z]. A source follower on VT5 is connected to the output of the emitter follower. This made it possible to completely eliminate the mutual influence of loads. connected to "Out.1" and "Out.2".

Details. Capacitors Sb...S 10 - type KT6. The remaining capacitors: ceramic - type K10-7V. K10-17. electrolytic - type K50-35. Coil L1 is wound on a ceramic ribbed frame (rib size - 15 mm) with silver-plated wire with a diameter of 1 mm with a pitch of 2 mm. The number of turns is 6.75. Winding is done with a heated wire under tension. Choke L2 - from black-and-white tube TVs (others can be used) with inductance from 100 to ZOOmkH. Resistors are MLT-0.125 type. Field-effect transistors can be used from any of the KPZOZ series. even better - from the KP307 series. High-frequency connectors X1...XZ - type SR50-73FV. Transistor VT3 - any high-frequency prp-type. VT4 - high-frequency RPR type.

Literature
1. Kotienko D.. Turkin N. LC-generator on field-effect transistors. - Radio. 1990. N5. p.59.
2. Wideband voltage repeater. - Radio. 1981. N4. p.61.
3. RF attenuator. - Radio amateur. KB and VHF. 1996. N10. p.36.
4. Mukhin V. Non-standard behavior of inductors when heated. - Radio amateur. 1996. N9. p.13. 14.
5. Maslov E. Calculation of an oscillatory circuit for stretched tuning. - Radio Amateur, 1995. N6. With. 14-16.

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.

(Fig. 12.1, 12.2) are made according to the traditional “inductive three-point” scheme, 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 connect 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.

Assembled according to the “capacitive three-point” circuit on bipolar and field-effect transistors, they 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, 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

current source, active element and 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 HL1 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.

Ma 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 shown. 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 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.

The note 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. On this day, 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 is adjusted through the active voltage (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.

To create narrowband noise generators, an LC or RC filter can be included at the output of the generator circuit.

HF generator

The proposed RF generator is an attempt to replace the bulky industrial G4-18A with a smaller and more reliable device. Usually, when repairing and setting up HF equipment, it is necessary to “lay” HF bands using LC circuits, check the signal passage along the RF and IF paths, adjust individual circuits to resonance, etc. Sensitivity, selectivity, dynamic range and other important parameters of HF devices are determined by circuit design solutions, so it is not necessary for a home laboratory to have a multifunctional and expensive RF generator. If the generator has a fairly stable frequency with a “pure sine wave”, then it is suitable for a radio amateur. Of course, we believe that the laboratory’s arsenal also includes a frequency meter, an RF voltmeter and a tester. Unfortunately, most of the tested HF generator circuits in the HF range produced a very distorted sine wave, which could not be improved without unnecessarily complicating the circuit. The RF generator, assembled according to the circuit shown in Fig. 1, has proven itself very well (the result is an almost pure sine wave throughout the entire HF range)

This design uses a variable capacitor type KPV-150 and a small-sized PM range switch (11P1N). With this KPI (10...150 pF) and inductors L2...L5, the HF range of 1.7...30 MHz is covered. As work on the design progressed, three more circuits (L1, L6 and L7) were added to the upper and lower sections of the range. In experiments with KPIs with a capacitance of up to 250 pF, the entire HF range was covered by three circuits.

The RF generator is assembled on a printed circuit board made of foil fiberglass laminate with a thickness of 2 mm and dimensions of 50x80 mm. The tracks and mounting spots are cut out with a knife and a cutter. The foil around the parts is not removed, but is used instead of “ground”. In the figure of the printed circuit board, for clarity, these sections of the foil are not shown.

The entire structure of the generator, together with the power supply (a separate board with a 9 V voltage stabilizer according to any circuit) is placed on an aluminum chassis and placed in a metal case of suitable dimensions. The front panel displays a range switch knob, a KPI adjustment knob, a small-sized RF connector (50 Ohm) and an LED indicator for powering on. If necessary, you can install an output level regulator (variable resistor with a resistance of 430...510 Ohms) and an attenuator with an additional connector, as well as a graduated scale. Unified sectional frames of the MF and DV ranges from obsolete radio receivers were used as the frames of the circuit coils. The number of turns of each coil depends on the capacity of the KPI used and is initially taken “with a reserve”. When setting up ("laying" the ranges) of the generator, some of the turns are unwound. Control is carried out using a frequency meter. Inductor L7 has a ferrite core M600-3 (NN) Ш2.8x14. Screens are not installed on circuit coils. The winding data of the coils, the boundaries of the subranges and the output levels of the RF generator are given in the table.

In the generator circuit, in addition to the indicated transistors, you can use field-effect ones KP303E(G), KP307 and bipolar RF transistors BF324, 25S9015, BC557, etc. Coupling capacitor C5 with a capacity of 4.7...6.8 pF - type KM, KT, KA with low RF losses. It is advisable to use high-quality ones (on ball bearings) as KPIs. With rigid installation, high-quality parts and warming up the generator for 10...15 minutes, you can achieve a frequency drift of no more than 500 Hz per hour at frequencies of 20...30 MHz. The signal shape and output level of the manufactured RF generator were checked using an S1-64A oscilloscope. At the final stage of setup, all inductors (except L1, which is soldered at one end to the body) are fixed with glue near the range switch and KPI.

Wideband generator

The range of generated frequencies is 10 Hz-100 MHz

Output voltage - 50 mV

Supply voltage - 1.5 V

Current consumption - 1.6 mA

Printed circuit board and front panel

Appearance


Simple RF Generator

To set up high-quality receiving equipment, you need an RF signal generator. The figure shows a diagram of such a generator operating in two ranges 1.6-7 MHz and 7-30 MHz. Smooth adjustment - three-section variable capacitor C1 with an air dielectric.

Schottky diode VD1 serves to stabilize the output RF voltage over a wide frequency tuning range.

Maximum output voltage 4 V, variable adjustableth resistor R4.

Coils L1 and L2 are wound on ferrite rods 2.8 mm long and 12 mm long from 100HH ferrite. L1 - 12 turns of PEV 0.12, L2 -48 turns of PEV 0.12. Winding is ordinary. Coil L3 is wound on a 7 mm ferrite ring, a total of 200 turns of PEV 0.12 in bulk.

HF generator