Power amplifier 10 W

The amplifier is designed to work with a transver having a P output of up to 1 watt. Exciter load, providing stable work on all ranges, is resistor R1. The setting consists of setting the quiescent current VT2 within 0.3 A (in the absence of a signal at the input).

A 1 volt signal at the input increases the output power in the antenna to 10 watts. Reception-transmission switching is carried out from an external control circuit, which is closed to the housing when switching to transmission. In this case, relay K1 is activated and connects the antenna to the output of the power amplifier. When the control circuit breaks, a positive voltage appears at the base of VT1, opening it. Accordingly, the VT1 collector is near zero. Transistor VT2 closes. Relay type RPV2/7 passport RS4.521.952 Chokes L1 and L2 type D1 (1A) with inductance 30 and 10 μH, respectively.

Frame diameter L3- 15 mm PEV2 wire 1.5 mm

Wideband power amplifier

To work in conjunction with an all-band HF transceiver, you can use a broadband power amplifier, the circuit diagram of which is shown in Fig. 1. In the ranges of 1.8-21 MHz, its maximum output power in telegraph mode with a power supply voltage of +50 V and a load resistance of 50 Ohms is about 90 W, in the range of 28 MHz - about 80 W. The peak output power in single-sideband amplification mode with an intermodulation distortion level of less than -36 dB is about 80 and 70 W, respectively. With well-selected amplifier transistors, the level of the second harmonic is less than 36 dB, the third harmonic is less than 30 dB in linear amplification mode and less than 20 dB in maximum power mode.

The amplifier is assembled using a push-pull circuit using powerful field-effect transistors VT1, VT2. The long line type transformer T1 provides the transition from an asymmetrical excitation source to the symmetrical input of a push-pull stage. Resistors R3, R4 allow you to match the input impedance of the cascade with a 50-ohm coaxial line with an SWR of no more than 1.5 in the range of 1.8 -30 MHz. Their low resistance provides the amplifier with very good resistance to self-excitation. To set the initial bias corresponding to the operation of the transistors in mode B, use the circuit Rl, R2, R5.

Installation of a mounted amplifier. The amplifier is assembled on a ribbed heat sink made of duralumin with dimensions of 110x90x45 mm. The fins are milled on both sides of the radiator, their number is 2x13, the thickness of each is 2 mm, the height is 15 mm on the side of the transistor installation and 20 mm on the side of the nuts for their fastening. On the longitudinal axis of the radiator, at a distance of 25 mm from the transverse axis, areas with a diameter of 30 mm are milled for installing transistors, and on the reverse side - for fastening nuts. Between the transistors, a “common wire” bus is laid on the radiator fins, cut from sheet copper 0.5 mm thick and attached to the base of the radiator with two M3 screws, passed between the two central ribs at distances of 10 mm from its edges. Tire dimensions - 90x40 mm. Mounting posts are attached to the bus. Coils L1 and L2 are frameless and wound with bare copper wire with a diameter of 1.5 mm on a mandrel with a diameter of 8 mm. With a winding length of 16 mm, they have five turns. Transformer T1 is wound with two twisted wires PEL.SHO 0.31 with a twist pitch of about three twists per centimeter on a ring magnetic core made of M400NN ferrite of standard size K10x6x5 and contains 2x9 turns. Transformers T2 and T3 are wound on ring magnetic cores made of ferrite of the same brand, standard size K32x20x6. Transformer T2 contains 2x5 turns of twisting from PELSHO 0.8 wires with a step of two twists per centimeter, T3 - 2x8 turns of such twisting. Capacitors Cl - C3 - type KM5 or KM6, C4-C7-KM4, C8-C11-KT3.

Setting up a properly assembled amplifier with serviceable parts comes down to adjusting the inductances of coils L1 and L2 for maximum output in the 30 MHz range by compressing or stretching the turns of the coils and setting the initial bias using resistor R1 to minimize intermodulation distortion in single-sideband signal amplification mode.

It should be noted that the level of distortion and harmonics largely depends on the accuracy of the selection of transistors. If it is not possible to select transistors with similar parameters, then for each transistor you should make separate circuits for setting the initial bias, and also, to minimize harmonics, select one of the resistors R3 or R4 by connecting additional ones in parallel with it.

In linear amplification mode in the ranges of 14-28 MHz, thanks to the presence of low-pass filters C8L1C10, C9L2C11, the harmonic level at the amplifier output does not exceed the permissible limit of 50 mW, and it can be connected directly to the antenna. In the ranges of 1.8-10 MHz, the amplifier should be connected to the antenna through a simple low-pass filter, similar to the C8L1C10 circuit, and two filters are sufficient, one for the ranges of 1.8 and 3.5 MHz, the other for the ranges of 7 and 10 MHz. The capacity of both capacitors of the first filter is 2200 pF, the second is 820 pF, the inductance of the coil of the first is about 1.7 μH, the second is about 0.6 μH. It is convenient to make coils frameless from bare copper wire with a diameter of 1.5 - 2 mm, wound on a mandrel with a diameter of 20 mm (the diameter of the coils is about 25 mm). The first filter coil contains 11 turns with a winding length of 30 mm, the second - six turns with a winding length of 25 mm. The filters are adjusted by stretching and compressing the turns of the coils to achieve maximum output in the ranges of 3.5 and 10 MHz. If the amplifier is used in overvoltage mode, separate filters should be turned on on each range.

The amplifier input can also be matched with a 75-ohm coaxial line. To do this, the values ​​of resistors R3, R4 are 39 Ohms.

The power consumed from the exciter will decrease by 1.3 times, but the gain cutoff in high-frequency ranges may increase. To equalize the frequency response, coils with an experimentally selected inductance, which should be about 0.1-0.2 μH, can be connected in series with capacitors C1 and C2.

The amplifier can be directly loaded into a resistance of 75 Ohms. Thanks to the action of the ALC loop, the linear undervoltage mode of its operation will remain, but the output power will decrease by 1.5 times.

Power amplifier on KP904

E. Ivanov (RA3PAO) When repeating the UY5DJ power amplifier (1), it turned out that the most critical component that reduces the reliability of the entire amplifier is the output stage. After experiments on various types

bipolar transistors had to switch to field-effect ones. The output stage of the UT5TA broadband amplifier (2) was taken as the basis. The diagram is shown in Fig. 1. new details are highlighted with thicker lines. A small number of parts made it possible to mount the cascade on printed circuit board

and a heatsink from UY5DJ in place of the parts and transistors of the UY5DJ amplifier. The quiescent current of the transistors is 100...200 mA.

The article below presents two circuits of simple amplifiers. H I buy it in a store, it’s cheaper to assemble an amplifier yourself, with characteristics sometimes no worse than store-bought ones.

Only a few parts are needed to assemble it. Even a novice radio amateur can handle assembling the amplifier. There are no inductors in it, the amplifiers are broadband and cover the entire range of the amplified signal, including UHF. In any case, the result was more than I expected. Most VHF local television and radio broadcasts began to be received with better quality, the picture became clearer.

Amplifier circuit diagram

The main part of this circuit is a high-frequency reverse conduction transistor (n-p-n) Q1 (2SC2570), a circuit specially designed for amplifying the VHF signal without an inductor.

If you plan to use the amplifier constantly, then you can exclude S2, which is needed to bypass the amplifier.

The amplifier is assembled on a circuit board.

Circuit board

Arrangement of elements on the circuit board

The second version of the circuit with an additional amplifier for the HF range

Schematic diagram of a dual-band HF/VHF amplifier

This circuit adds an HF field-effect transistor amplifier (Q1 MFE201 N-channel two-gate and Q2 (and 2SC2570 n-p-n RF silicon transistor), which provide two independent amplifiers switched by switch S1. The result is a simple active antenna designed to amplify signals from 3 to 3000 MHz (three ranges: 3-30 MHz high-frequency (HF) signals; 3-300 MHz very-high-frequency (VHF) signals; 300-3000 MHz ultra-high frequency (UHF) signals.

Amplifier PCB

Arrangement of elements

P O P U L A R N O E:

You can easily and simply make a fantastically beautiful flower from felt - daisy.

If you sew several of these flowers in different shades, then you can decorate them in an interesting way, for example, a gift, a sofa cushion, a decorative wreath, etc.

To decorate a bag, flowers can be used as pendants.

In addition, you can sew the daisy onto a hair hoop or attach it to a hairpin.

ElectroM 3D - Free program for drawing, calculating and displaying electrical circuits in 3D.

ElectroM 3D- simple free program for beginner radio amateurs. Previously we looked at similar program — . ElectroM 3D more simple program. In it you can create the simplest electrical circuits and visually see how they will work. The circuit can use a battery, a switch, light bulbs, rheostats, diodes, etc. All your experiments can be observed in beautifully made three-dimensional mode!

High frequency amplifiers (UHF) are used to increase the sensitivity of radio receiving equipment - radios, televisions, radio transmitters. Placed between the receiving antenna and the input of the radio or television receiver, such UHF circuits increase the signal coming from the antenna (antenna amplifiers).

The use of such amplifiers makes it possible to increase the radius of reliable radio reception; in the case of radio stations (receive-transmit devices - transceivers), either increase the operating range, or, while maintaining the same range, reduce the radiation power of the radio transmitter.

Figure 1 shows examples of UHF circuits often used to increase radio sensitivity. The values ​​of the elements used depend on specific conditions: on the frequencies (lower and upper) of the radio range, on the antenna, on the parameters of the subsequent stage, on the supply voltage, etc.

Figure 1 (a) shows broadband UHF circuit according to the common emitter circuit(OE). Depending on the transistor used, this circuit can be successfully applied up to frequencies of hundreds of megahertz.

It is necessary to recall that the reference data for transistors provides maximum frequency parameters. It is known that when assessing the frequency capabilities of a transistor for a generator, it is enough to focus on the limiting value of the operating frequency, which should be at least two to three times lower than the limiting frequency specified in the passport. However, for an RF amplifier connected according to the OE circuit, the maximum nameplate frequency must be reduced by at least an order of magnitude or more.

Fig.1. Examples of simple amplifier circuits high frequency(UHF) on transistors.

Radio elements for the circuit in Fig. 1 (a):

• R1=51k (for silicon transistors), R2=470, R3=100, R4=30-100;
• C1=10-20, C2= 10-50, C3= 10-20, C4=500-Zn;

Capacitor values ​​are given for VHF frequencies. Capacitors such as KLS, KM, KD, etc.

Transistor stages, as is known, connected in a common emitter (CE) circuit, provide relatively high gain, but their frequency properties are relatively low.

Transistor stages connected according to a common base (CB) circuit have less gain than transistor circuits with OE, but their frequency properties are better. This allows the same transistors to be used as in OE circuits, but at higher frequencies.

Figure 1 (b) shows wideband high frequency amplifier circuit (UHF) on one transistor turned on according to a common base scheme. The LC circuit is included in the collector circuit (load). Depending on the transistor used, this circuit can be successfully applied up to frequencies of hundreds of megahertz.

Radio elements for the circuit in Fig. 1 (b):

• R1=1k, R2=10k. R3=15k, R4=51 (for supply voltage ZV-5V). R4=500-3 k (for supply voltage 6V-15V);
• C1=10-20, C2=10-20, C3=1n, C4=1n-3n;
• T1 - silicon or germanium RF transistors, for example. KT315. KT3102, KT368, KT325, GT311, etc.

Capacitor and circuit values ​​are given for VHF frequencies. Capacitors such as KLS, KM, KD, etc.

Coil L1 contains 6-8 turns of PEV 0.51 wire, brass cores 8 mm long with M3 thread, 1/3 of the turns are drained.

Figure 1 (c) shows another broadband circuit UHF on one transistor, included according to a common base scheme. An RF choke is included in the collector circuit. Depending on the transistor used, this circuit can be successfully applied up to frequencies of hundreds of megahertz.

Radioelements:

• R1=1k, R2=33k, R3=20k, R4=2k (for supply voltage 6V);
• C1=1n, C2=1n, C3=10n, C4=10n-33n;
• T1 - silicon or germanium RF transistors, for example, KT315, KT3102, KT368, KT325, GT311, etc.

The values ​​of capacitors and circuit are given for frequencies of the MF and HF ranges. For higher frequencies, for example, for the VHF range, the capacitance values ​​should be reduced. In this case, D01 chokes can be used.

Capacitors such as KLS, KM, KD, etc.

L1 coils are chokes; for the CB range these can be coils on rings 600NN-8-K7x4x2, 300 turns of PEL 0.1 wire.

Higher gain value can be obtained by using multi-transistor circuits. These can be various circuits, for example, made on the basis of an OK-OB cascode amplifier using transistors of different structures with serial power supply. One of the variants of such a UHF scheme is shown in Fig. 1 (d).

This UHF circuit has significant gain (tens or even hundreds of times), but cascode amplifiers cannot provide significant gain at high frequencies. Such schemes are usually used at frequencies in the LW and SV ranges. However, with the use of ultra-high frequency transistors and careful design, such circuits can be successfully applied up to frequencies of tens of megahertz.

Radioelements:

• R1=33k, R2=33k, R3=39k, R4=1k, R5=91, R6=2.2k;
• C1=10n, C2=100, C3=10n, C4=10n-33n. C5=10n;
• T1 -GT311, KT315, KT3102, KT368, KT325, etc.
• T2 -GT313, KT361, KT3107, etc.

The capacitor and circuit values ​​are given for frequencies in the CB range. For higher frequencies, such as the HF band, capacitance values ​​and loop inductance (number of turns) must be reduced accordingly.

Capacitors such as KLS, KM, KD, etc. Coil L1 - for the CB range contains 150 turns of PELSHO 0.1 wire on 7 mm frames, trimmers M600NN-3-SS2.8x12.

When setting up the circuit in Fig. 1 (d), it is necessary to select resistors R1, R3 so that the voltages between the emitters and collectors of the transistors become the same and amount to 3V at a circuit supply voltage of 9 V.

The use of transistor UHF makes it possible to amplify radio signals. coming from antennas, in television bands - meter and decimeter waves. In this case, antenna amplifier circuits built on the basis of circuit 1(a) are most often used.

Antenna amplifier circuit example for frequency range 150-210 MHz is shown in Fig. 2 (a).

Fig.2.2. MV antenna amplifier circuit.

Radioelements:

• R1=47k, R2=470, R3= 110, R4=47k, R5=470, R6= 110. R7=47k, R8=470, R9=110, R10=75;
• C1=15, C2=1n, C3=15, C4=22, C5=15, C6=22, C7=15, C8=22;
• T1, T2, TZ - 1T311(D,L), GT311D, GT341 or similar.

Capacitors such as KM, KD, etc. The frequency band of this antenna amplifier can be expanded in the area low frequencies a corresponding increase in the capacities included in the circuit.

Radio elements for the antenna amplifier option for the range 50-210 MHz:

• R1=47k, R2=470, R3= 110, R4=47k, R5=470, R6= 110. R7=47k, R8=470. R9=110, R10=75;
• C 1=47, C2= 1n, C3=47, C4=68, C5=47, C6=68, C7=47, C8=68;
• T1, T2, TZ - GT311A, GT341 or similar.

Capacitors such as KM, KD, etc. When repeated of this device all requirements must be met. requirements for installation of HF structures: minimum lengths of connecting conductors, shielding, etc.

Antenna amplifier designed for use in the bands television signals(and higher frequencies) can be overloaded with signals from powerful CB, HF, and VHF radio stations. Therefore, a wide frequency band may not be optimal because this may interfere with the amplifier's normal operation. This is especially true in the lower region of the amplifier's operating range.

For the circuit of the given antenna amplifier, this can be significant, because The slope of the gain decay in the lower part of the range is relatively low.

You can increase the steepness of the amplitude-frequency response (AFC) of this antenna amplifier by using 3rd order high pass filter. To do this, an additional LC circuit can be used at the input of the specified amplifier.

The connection diagram for an additional LC high-pass filter to the antenna amplifier is shown in Fig. 2(b).

Additional filter parameters (indicative):

• C=5-10;
• L - 3-5 turns PEV-2 0.6. winding diameter 4 mm.

It is advisable to adjust the frequency band and frequency response shape using appropriate measuring instruments (sweeping frequency generator, etc.). The shape of the frequency response can be adjusted by changing the values ​​of capacitors C, C1, changing the pitch between turns L1 and the number of turns.

Using the described circuit solutions and modern high-frequency transistors (ultra-high-frequency transistors - microwave transistors), you can build an antenna amplifier for the UHF range. This amplifier can be used either with a UHF radio receiver, for example, part of a VHF radio station, or in conjunction with a TV.

Figure 3 shows UHF antenna amplifier circuit.

Fig.3. UHF antenna amplifier circuit and connection diagram.

Main parameters of the UHF range amplifier:

• Frequency band 470-790 MHz,
• Gain - 30 dB,
• Noise figure -3 dB,
• Input and output resistance- 75 Ohm,
• Current consumption - 12 mA.

One of the features of this circuit is the supply of supply voltage to the antenna amplifier circuit through the output cable, through which the output signal is supplied from the antenna amplifier to the radio signal receiver - a VHF radio receiver, for example, a VHF radio receiver or TV.

The antenna amplifier consists of two transistor stages connected in a circuit with a common emitter. A 3rd order high pass filter is provided at the input of the antenna amplifier, limiting the range of operating frequencies from below. This increases the noise immunity of the antenna amplifier.

Radioelements:

• R1 = 150k, R2=1k, R3=75k, R4=680;
• C1=3.3, C10=10, C3=100, C4=6800, C5=100;
• T1, T2 - KT3101A-2, KT3115A-2, KT3132A-2.
• Capacitors C1, C2 are type KD-1, the rest are KM-5 or K10-17v.
• L1 - PEV-2 0.8 mm, 2.5 turns, winding diameter 4 mm.
• L2 - RF choke, 25 µH.

Figure 3 (b) shows a diagram of connecting the antenna amplifier to the antenna socket of the TV receiver (to the UHF selector) and to a remote 12 V power source. In this case, as can be seen from the diagram, power is supplied to the circuit through the coaxial cable used and for transmitting an amplified UHF radio signal from an antenna amplifier to a receiver - a VHF radio or to a TV.

Radio connection elements, Fig. 3 (b):

• C5=100;
• L3 - RF choke, 100 µH.

The installation is carried out on double-sided fiberglass SF-2 in a hinged manner, the length of the conductors and the area of ​​the contact pads are minimal, it is necessary to provide careful shielding of the device.

Setting up the amplifier comes down to setting the collector currents of the transistors and are regulated using R1 and RЗ, T1 - 3.5 mA, T2 - 8 mA; the shape of the frequency response can be adjusted by selecting C2 within 3-10 pF and changing the pitch between turns of L1.

Literature: Rudomedov E.A., Rudometov V.E - Electronics and spy passions-3.

We continue the conversation about the direct amplification transistor receiver, which began at the seventh workshop. By then connecting the detector receiver to a single-stage low-frequency amplifier, you thereby turned them into a 0-V-1 receiver. Then I assembled a single-transistor reflex receiver, and at the previous workshop I added a two-stage low-frequency amplifier to it - the result was a 1-V-3 receiver. Now try adding a high frequency (HF) modulated preamp stage to it to make it a 2-V-3 receiver. The sensitivity in this case will be sufficient to receive not only local, but also distant broadcasting stations on the magnetic antenna.

What is required for such a single-stage RF amplifier? Basically - a low-power high-frequency transistor of any of the P401...P403, P416, P422, GT308 series, as long as it is in good working order, several capacitors, a resistor and a ferrite ring of grade 600NN with an outer diameter of 8...10 mm. The coefficient h21E of the transistor can be in the range of 50...100. You should not use a transistor with a large static current transfer coefficient - an experienced amplifier will be prone to self-excitation.

Schematic diagram amplifier is shown in Fig. 56. The amplifier itself is formed only by a transistor V1 and resistors R1, R2. Resistor R2 acts as a load, and the base resistor R1 determines the operating mode of the transistor. The collector load of the transistor can be a high-frequency choke - the same as in a reflex receiver.

Custom contour L1 C1 and communication coil L2 refer to the input circuit, capacitor C2- dividing. This part is an exact repetition of the input part of the receiver you have already tested. Capacitor Immediately, resistor R, diode V2, phones B1 s The blocking capacitor Sbl forms a detector circuit necessary for testing the amplifier.

How does such an amplifier work? Fundamentally the same as a single-stage low-frequency amplifier. It only amplifies not audio frequency oscillations, like that amplifier, but modulated high frequency oscillations coming to it from the coupling coil L2. The high-frequency signal, amplified by the transistor, is allocated to the load resistor R2 (or other collector load) and can be fed to the input of a second stage for additional amplification or to a detector to convert it into a low-frequency signal.

Mount the amplifier parts on a temporary (cardboard) board, as shown on the right in Fig. 56. Move here and connect the parts of the input circuit (L1C1) and the communication coil (L2) of the receiver to the amplifier. Don't forget to include an isolating capacitor in the coupling coil circuit C2. Connect the battery voltage 9 V and, choosing a base resistor R1, set the collector current of the transistor within 0.8...1.2 mA. Don’t forget: the resistance of the base resistor should be greater, the greater the static current transfer coefficient of the transistor (the value of this resistor indicated in the diagram corresponds to the coefficient h21E transistor about 50).

Now mount a detector circuit on a separate small cardboard, connecting in series the phones B1 with a blocking capacitor Sbl with a capacity of 2200..3300 pF, a point diode V2 any series and separator nyu capacitor Immediately with a capacity of 3300...6800 pF, Resistor resistance R maybe 4.7...6.8 kOhm. Connect this circuit between the collector and emitter of the transistor, that is, to the output of the amplifier, and connect an external or indoor antenna and, of course, grounding. When tuning the input circuit to the wave of a local radio station, its high-frequency signal will be amplified by the transistor VI, detected by diode V2 and converted by phones IN 1 into sound. Resistor R in this circuit is necessary for normal operation of the detector. Without it, phones will sound quieter and distorted.

For the next experiment with an RF amplifier, a high-frequency step-down transformer is needed (Fig. 57). Wind it on a ring of 600NN grade ferrite (the same as the core of the high-frequency choke of the reflex stage of the receiver). Its primary winding L3 should contain 180..200 turns of wire PEV or PEL 0.1...0.12, and the secondary L 4 60...80 turns of the same wire.

Connect winding L3 of the high-frequency transformer to the collector circuit of the transistor instead of the load resistor, and to its winding L4 connect the same detector circuit as in the previous experiment, but without the coupling capacitor and resistor, which are not needed now. How does it sound now? phones? Louder. This is explained by better matching of the output impedance of the amplifier and input impedance detector target.

And now, using the diagram shown in Fig. 58, connect this single-stage amplifier to the input of the 1-V-3 reflex receiver transistor. The RF receiver amplifier became two-stage. The connecting element between the cascades was the coil L4 high-frequency transformer included in the base circuit of transistor V 2 (in the receiver 1-V-Z the transistor W1 was used) instead of the communication coil (there was L2) with the former input configurable circuit. Now an external antenna and grounding are not needed - reception is carried out using the magnetic antenna W1. whose role: is performed by a ferrite rod with a coil located on it L1 input configurable circuit L1 C1.

So, together with a two-stage low-frequency amplifier, a four-transistor direct amplification receiver 2-U-W was trained. The receiver may be self-exciting. This is because, firstly, it is reflexive, and reflexive receivers are generally prone to self-excitation, and secondly, the conductors connecting the experimental amplifier cascade with the reflex cascade are long. If the new stage, together with the magnetic antenna, is mounted compactly on the same receiver board, making the circuits as short as possible, there will be fewer reasons for self-excitation. This is also facilitated by the decoupling filter cell. R2 C3 in the negative power circuit of the first transistor of the RF amplifier, which eliminates the connection between the stages through a common lithium source and thereby prevents self-excitation of the high-frequency path of the receiver.

But the second stage of the RF amplifier may be the same as the first, that is, not reflexive, and the connection between them may not be a transformer. Diagram possible option amplifier is shown in Fig. 59. Here the load of the transistor V1 the first stage, as in the first experiment of this workshop (see Fig. 56), is resistor R2; The high-frequency signal voltage created across it through a capacitor NW supplied to the base of the transistor V2 the second cascade, exactly the same as the first. The signal, additionally amplified by the transistor of the second stage, is removed from its load resistor R4 ( the same; like R 2) and through capacitor C 4 (such as NW) goes to the detector on diode V 3, is detected by it, and the low frequency oscillations created across its load resistor R5, are fed to the input of the bass amplifier.

In this version, the second cascade and detector are like an unfolded reflex cascade of the previous version. But the transistor only amplifies high-frequency oscillations. And if you connect it to a two-stage low-frequency amplifier, you get a direct amplification receiver 2- V-2. The amplification of the low-frequency signal will decrease somewhat, telephones or the loudspeaker head at the output of such a receiver will sound a little quieter, but the danger of self-excitation of its high-frequency path will be reduced. This loss can be partially compensated by increasing the voltage of the low-frequency signal at the output of the detector by including a second diode in the detector cascade (shown in dashed lines in Fig. 59 V4), as you did in one of the experiments in the seventh workshop (see Fig. 50), or use a transistor in the detector cascade.

Try to experiment with low-frequency amplifier options, compare the quality of their work and draw appropriate conclusions for the future.

One more tip. When experimenting with one or another version of the receiver, draw and remember its complete circuit diagram. For what? A radio amateur, even a beginner, must draw diagrams of such devices from memory. The circuit diagram will also help you better understand the operation of the receiver as a whole and its parts, and will make it easier to find faults in it.

Literature: Borisov V.G. Workshop for a beginner radio amateur. 2nd ed., revised. and additional - M.: DOSAAF, 1984. 144 p., ill. 55k.