Push-pull tube amplifier on GU 19. Music Angel - Tube amplifiers - Recommendations for repeating a replica of the Williamson-Hafler-Keroes circuit
UM on two GU29
V. Milchenko RZ3ZA
The amplifier is assembled on two parallel-connected GU-29 lamps. The input signal amplitude is 1...1.5 volts. Anode current is 400...450 mA. Output power at a load of 75 ohms - 150 watts.
In transmission mode, the KT920B transistor is supplied with a voltage of -15 volts, a quiescent current, a quiescent current of the transistor (without a signal) of -120 mA. It can be adjusted within small limits by selecting resistor R3. Transformer T1 is shunted with a 2k resistor. The quiescent current of the lamps is set automatically by two D815D zener diodes connected in series and for two lamps it is 70-80 mA. The lamps are located horizontally in a housing 300x300x80 mm. The T1 transformer is wound on a cylindrical frame with a 600NN ferite core.
Literature: magazine "Radio Amateur" No. 8 1997
PA on two 6P45S lamps
Hybrid PA with transformerless power supply
E. Golubev, RV3UB
PA with transformerless power supply and protection
As an example, a PA circuit with a power supply protected from phase reversal with zero is shown. The entire article can be read: Radio magazine, 1969, No. 3, page 19
RADIO STATION POWER AMP CATEGORY 1
Literature: "Radio" 1979 No. 11 G. Ivanov (U0AFX)
Transformerless power supply to the PA
PA for CB radio station
This power amplifier is designed to operate a portable radio station in stationary mode. In this case, the signal from its output is fed to the input of the amplifier through a coaxial cable. The power of a portable radio station with an input impedance of 50 Ohms of a power amplifier is 1-2W. This power amplifier develops power up to 30-40W. The output is designed for a 75 ohm antenna.
The amplifier circuit is shown in the figure
The signal from the transmitter output is sent to input X2 to the input of the double lamp VL1 GU-29, the signal goes to the control grids of this lamp. R7 brings the amplifier's input impedance to 50 ohms. The anode load of the lamp is inductor L2, from which the signal goes to the U-shaped filter L1 C3 C4 and then goes to the antenna. The output stage of the transmitter is equipped with an SWR meter that allows you to measure both forward and reflected SWR. This makes it possible to configure the output circuit using capacitors C3 C4.
The power source is transformer, it contains 2 rectifiers and three parametric stabilizers.
L1 is wound with copper wire (bare) with a diameter of 2 mm, without a frame, winding diameter 25 mm, winding length 22 mm, number of turns 8. L2 is wound on a frame with a diameter of 20 mm and contains 150 turns of PELSHO 0.25, winding length 80 mm. L3 L4 are wound on resistors R2 R4, they contain 5 turns of PEV 1.0. L5 L6 - chokes DM-0.5. T1 - 6 turns of PEV 0.31 with a tap from the middle, wound on the inner core of the coaxial cable, which goes from L1 to the output connector (the shielding braid is removed at the point of winding).
T2 is wound on a magnetic circuit Ш25*32, winding 1 -1030 turns PEV 0.25, 2-1300 turns PEV 0.25, 3-60 turns PEV 1.0 with a tap from the middle, winding 4 contains 175 turns PEV 0.2.
The amplifier is mounted in a metal case with volumetric installation. If necessary, it is necessary to remove heat using a fan to blow over the lamp.
R8 sets the lamp quiescent current within 15-17mA. the alternating control voltage supplied to the lamp grids (U on R7) should be about 10V and not exceed 15V.
Amplifier using 6P42S tubes
The difficulty of obtaining average power levels (about 100 W) in transistor silos forces us to look for other solutions. It may be as suggested by Muscovite V. Krylov (RV3AW). He created a push-pull amplifier using two 6P42S tubes operating at a supply voltage of only 300 V. The output power of the amplifier is 130 W with an input power of about 5 W.
Push-pull switching of the lamps allows one to significantly (up to 20 dB) reduce the radiation at the second harmonic compared to a conventional amplifier. A broadband transformer T1 with a transformation ratio of 4 is installed in the anode circuit of the lamps. As a result, the amplitude of the RF voltage on the output P-circuit is halved and it becomes possible to use a standard KPI from a broadcast receiver. The simplicity of the device and the availability of the element base make it possible to recommend this power amplifier for repetition. The diagram is shown in Fig.
Coil L2 is made on a plastic ring (standard size K64x60x30) with MGTF wire with a core cross-section of 0.5 mm. Branches are made from 2, 4, 8, 12 and 20 turns. Transformer T1 is made on a magnetic core of two rings with standard size K40x25x25 made of 2000NN ferrite. The windings contain 12 turns of MGTF wire with a core cross-section of 0.5 mm. Transformer T2 is made on two ferrite (2000NN) rings with standard size K16x8x6 folded together. Each winding consists of 8 turns of MGTF wire with a core cross-section of 0.15 mm2. Winding T1 and T2 was carried out simultaneously with three wires.
Transformerless RA on GU-29
I.Avgustovsky (RV3LE)
The idea of building a push-pull amplifier using electronic tubes is not new, and the circuitry of this amplifier, in principle, is no different from the circuitry of building push-pull amplifiers using transistors. It should be noted that current lamps work best in this circuit, i.e. lamps with low internal resistance, which are capable of providing a significant pulse of anode current at a low supply voltage. These are lamps of the 6P42S, 6P44S and 6P45S types. However, I was able to build an amplifier with good characteristics using a GU-29 type lamp.
The range of amplified frequencies is 3.5...29.7 MHz.
The power supplied to the anode circuit is 150 W.
Efficiency - 65%.
Output power at a 75 Ohm antenna equivalent in the ranges:
o 3.5...21 MHz-- 100 W;
o 24 MHz - 90 W;
o 28 MHz - 75 W.
Power consumed from the network at rated network voltage and maximum output power is 200 W.
Dimensions:
o width - 160 mm;
o height - 150 mm;
o depth - 215 mm.
Weight - no more than 2 kg.
A distinctive feature of this amplifier is its transformerless power supply circuit. The advantages of such a power supply scheme are obvious - with an input power of 150 W, taking into account the efficiency of the power source, a power transformer with an overall power of at least 200 W is required. In this case, the dimensions and weight of the power supply itself are comparable to the parameters of the power amplifier itself and far exceed the dimensions and weight of an amplifier with an input power of 500 W using 6P45S lamps.
I made this amplifier as an experimental amplifier back in 1994, but from the very first day of operation it showed itself so well that it works to this day without any modifications. During this time, more than 10,000 QSOs were conducted on it. All correspondents invariably note the excellent quality of the signal. Despite the fact that my antennas are located at a distance of only 2...3 meters from the collective television antennas, TVI is completely absent.
I would also like to note that the GU-29 lamp in this design is operated in a very harsh mode (input power is 150 W), but despite this, over two and a half years of operation I have not detected any deterioration in power characteristics. Let's look at the circuit diagram (Fig. 1).
The input signal is fed to the primary winding of a wideband transformer based on the T1 line. Non-inductive resistor R1 is an active load of the power amplifier of the transceiver itself and allows us to obtain a linear frequency response of the latter.
The amplified anti-phase signal from the anodes of the lamp is supplied to transformer T2, the anode voltage is supplied to the middle point of the primary winding. The amplifier load is switched on through a conventional P-circuit, the signal to which is taken from the secondary winding of transformer T2.
The amplifier is powered through a rectifier assembled according to a voltage doubling circuit using diodes VD1, VD2 and capacitors C10, C11 (Fig. 2).
The screen grid voltage (+225 V) is stabilized. The bias voltage is obtained from a separate rectifier VD5, C9 from the secondary winding of the incandescent transformer T3.
Special attention should be paid to the fact that none of the sources powering the amplifier (~6.3V, 0, -Ucm, +225 V, +600 V) is connected to the chassis! The amplifier chassis is used as a common wire only at high frequency.
Amplifier parts and designs
Since galvanic isolation of the power circuits from the chassis is carried out through transformers T1 and T2, special attention should be paid to the care of their manufacture. Transformer T1 is wound on a ferrite ring of the M30VCh brand with an outer diameter of 16 mm (20 mm is possible). First remove sharp edges from the ring with fine sandpaper. Then the ring is wrapped with at least three layers of fluoroplastic tape. The transformer is wound simultaneously with three wires in fluoroplastic insulation MGTF-0.12 without twisting. Number of turns - 12.
Transformer T2 is similar in design to T1, but is made on two M30VCh rings folded together with an outer diameter of 32 mm (36 mm is possible). The windings of the T2 transformer also contain 3x12 turns of MGTF-0.14 wire without twisting. The ends of the windings are fixed with threads. Polyethylene film should not be used as insulation due to its non-heat resistance.
I do not give the parameters of the P-circuit; they can be easily calculated using existing methods. In the author’s version, the L3 coil is wound on a fluoroplastic ring with an outer diameter of 70 mm and a cross-section of 15x15 mm2 with a silver-plated wire with a diameter of 1.5 mm and its taps are held on a ceramic biscuit of the SA1.2 range switch. Capacitor C5 is a tuning capacitor with an air dielectric of the KPV-150 type. C8 - standard two-section PCB 2x12...495 pF from broadcast receivers.
All blocking capacitors C1...C4, C12...C14 are of the KSO type for a voltage of at least 500 V or similar with a nominal value of 0.01...0.1 µF.
In the power supply (Fig. 2) there are diodes VD1 and VD2 - KD226G or KD203A, which allow a large current pulse, inevitable at the moment the power is turned on, since this design does not have a large inductance in the form of a power transformer. The charging current of capacitors C10 and C11 reaches tens of amperes within a few milliseconds, therefore, to protect the diodes VD1 and VD2 from breakdown, a resistor R6 is installed. Its rating is not critical and can range from 330 Ohms to 1 kOhm. A few seconds after turning on the amplifier, it is shorted out by toggle switch SA3 “Anode”. Resistors R7 and R8 serve to equalize the voltage on capacitors C10 and C11.
Transistor VT1 and zener diodes VD3 and VD4 are installed on small radiators isolated from the chassis. Trimmer resistor R9 - any type, but with good insulation. Filament transformer - with an overall power of at least 20 W and with well-insulated windings.
Anticipating a question from readers about possible replacements for ferrite rings for transformers T1 and T2, I want to say the following: rings with a permeability of 30 HF can be replaced without damage with any of the specified standard sizes with a permeability of 20 HF...50 HF. I have not experimented with rings with a permeability of 100 NN...600 NN, but rings with a permeability of 1000 NM...3000 NM obviously will not work here.
The power supply and the amplifier lamp have galvanic contact with the network, so care should be taken during the setup process. Once again I draw your attention: the “0V” circuit should not have contact with the chassis! The input (before T1) and output (after T2) circuits of the amplifier are absolutely safe and must be connected to the chassis according to the diagram.
Linear power amplifier for SSB/CW/AM
With an input power of 200 W, the output power is 120...130 W. The amplifier operates on two GU-50 pentodes according to a circuit with three grounded gridsThe input impedance of the amplifier is 50...70 Ohms, which allows you to connect it to the exciter with a piece of coaxial cable with the same characteristic impedance.
To achieve a current of 200 mA at an anode voltage of 1200 V, an excitation power of 7...10 W is required. The quiescent current is several milliamps. Peak power (input) can be driven up to 400 watts when amplifying single sideband signals without harming the tubes, since the average power input will be around 200 watts. Choke Dr1 with an inductance of about 300...500 µH should be designed for a current of 200...250 mA
Power amplifier for SDR – 1000
This power amplifier is designed to work in conjunction with the software-defined transceiver SDR-1000, the output power of which is about 0.5 W, although the output power is stated to be at least one Watt. In addition, it can be used in conjunction with any type of transceiver radio receiver, for example, R-326M, R-399A, R-160P.
The power amplifier consists of two stages: a broadband voltage amplifier made on transistors VT1 and VT2, operating in class A - driver, and the power amplifier itself, which uses two GU-29 lamps connected in parallel and operating in class AB1.
This amplifier was designed and manufactured for everyday on-air work, where its output power is more than enough. GU-29 lamps were used due to their fairly good linearity and availability. The amplifier has an output power of about 100 W on all bands. The input voltage is 3 Volts, due to the use of an attenuator made on resistors R15..R17, which attenuates the input signal by 14 dB (5 times the voltage). If the output voltage that must be supplied to the amplifier input is less than 3 volts, then you can install an attenuator with less attenuation, or abandon it altogether. The sensitivity of the cascode voltage amplifier on transistors VT1 and VT2 (driver) is quite high and equals 0.5 V. The housing dimensions are 137 x 240 x 240 mm, which was determined by what was available.
The power amplification stage used a common cathode circuit with excitation voltage applied to the grid. When the RA is operating, the input signal through the RF connector XW1 and relay contacts K1.1, the attenuator, is fed to the input of a U-shaped low-pass filter (LPF), the cutoff frequency of which is 47 MHz. Low-pass filter - C11, L6, C13, plus the input capacitance of transistor VT2 has a Butterworth characteristic, with a rolloff in the amplitude-frequency characteristic at the cutoff frequency equal to 3 dB. The use of low-pass filters is useful for several reasons. The first is a decrease in the level of higher harmonics, the second: the low-pass filter compensates for the input capacitance of the transistor VT2, as a result of which the input resistance RA becomes frequency-independent, and the amplitude of the exciting signal does not fall with increasing frequency. Without a low-pass filter in the upper ranges it would have fallen by more than 35...45%. In addition, the low-pass filter helps to obtain a good standing wave ratio (SWR) at the input of the power amplifier. As a result, the transceiver operates at a matched load. As you can see, the use of a low-pass filter is more than justified. The low-pass filter output is loaded onto the driver's input impedance, which is adjusted to 50 Ohms. From the driver load resistance R14, the amplified high-frequency voltage is supplied to the control grids of the VL1 and VL2 lamps. The gain of each lamp is 50 / 14 = 3.57 times the voltage, or 12.75 times the power, which is 11.1 dB. This is, of course, not much, but more is not required. The task of filtering spurious oscillations at the amplifier input was not set, since the output circuits of the transceiver cope with this. Although, of course, there is some filtering of higher harmonics. In this case, two lamps connected in parallel operate on a common load, P – circuit.
Relays K3 and K4, which close a piece of coaxial cable used for “Bypass” to the housing from both ends in transmission mode, increase the stability of the power amplifier.
Throttle4 and capacitor C17 serve to protect the power supply from possible VHF oscillations during self-excitation of the RA. At the output of the P-circuit, for ease of adjustment, a high-frequency voltmeter is installed. In transmission mode, when the pedal is pressed, the electronic key made on transistor VT2 (see Fig. 2) comes into action, transistor VT2 opens and relays K1 ... K5, included in its collector circuit, are activated. Relay contacts K5.1, in Figure 2, switches, and the lamp screen grids are supplied with supply voltage from a voltage stabilizer made on transistor VT1, which, despite its simplicity, showed good results. Resistor R6, which is connected to the output of the stabilizer, increases the stability of the voltage stabilizer in receive mode. The operation of the stabilizer can be further improved by using a light bulb instead of ballast resistor R4 for the appropriate voltage and current, which will play the role of a barter, improving the stabilization coefficient.
Power transformer Tr.1 of the power supply is connected to the network smoothly through the current-limiting resistor R1, which is then short-circuited by the contacts of toggle switch B1 having a middle neutral position. This simple connection circuit significantly extends the life of the lamp and power transformers, and the entire RA in general. It is known that the filament of a cold lamp has a resistance several times less than the filament of a heated lamp. Consequently, the inrush current of the lamp filament is several times higher than the rated filament current of the lamp. Such a high switching current overloads the filament, destroys its structure, and reduces the life of the lamp. Therefore, the use of soft start is more than justified. The anode power supply has protection against excess anode current. Resistor R11 in Fig. 1 limits the current during breakdown, or short circuit of the output of the anode voltage source at a level equal to 535 / 10 = 53.5 A. The FR207 type diodes used will withstand this current pulse and will not fail. The anode power source is made according to a doubling circuit and has fairly good dynamic characteristics, which is ensured by sufficiently large capacitance values of the electrolytic capacitors used in the circuit.
All parts related to the high-frequency unit are connected to each other by 20 mm wide bars, which are cut from tinned tin from instant coffee cans. Connected to the bus bars: lamp cathodes, current collectors of variable capacitors included in the P circuit, antenna connector, ground terminal, blocking capacitors in the anode choke circuit. Particular care should be taken to connect the current collectors of the variable capacitors (variable capacitors), the grounded terminals of additional capacitors connected to them, and the cathodes of the lamps to the bus. Between the grounding points of the KPI and the cathodes of the lamps there should be no grounding of other parts going to the housing, since a large loop current flows between them.
The input capacitances of the low-pass filter (C11, C13) are made up of two capacitors of type KT-2; you can use one capacitor of type KT-2, the value of which is selected using instruments.
Dr.1 contains 7 turns wound on a mandrel with a diameter of 10 mm with high-resistance nichrome wire with a diameter of 0.8 mm. Throttle length 25 mm, outlet from the middle.
Dr.4 contains 5 turns wound with PEV-2 1.3 mm wire on a mandrel with a diameter of 10 mm, winding length 18 mm. Inductance coil L6 of the low-pass filter input filter contains 8 turns of PEV-2 1.2 wire. Winding frameless, diameter 8 mm? Winding length 14.5 mm. The low-pass filter, attenuator, and driver are enclosed in one common screen, located near the radio tube panels under the chassis.
The anode KPI was taken from some industrial equipment.
Loop coil data is given below. The taps are always counted from the hot end (anode).
Coil L4 has 9 turns of frameless winding, diameter is 30 mm, winding length is 32 mm, wound with silver-plated wire with a diameter of 3 mm, tapping from the 3rd and 6th turns..
The L5 coil is wound on a frame with a diameter of 40 mm. Contains 25 turns, wire diameter is 1.2 mm, winding length is 40 mm. Bends from the 6th and 13th turns.
The anode choke is wound on a fluoroplastic rod with a diameter of 18 mm, the winding length is 90 mm, the wire is 0.4 mm, the tap is from the middle.
Relays K1, K3 and K4 type RES-49, passport RS4.569.421-00. Relay K2 is type REN-33, passport RF45 100021-0002, Power transformer Tr1 is used type TS-180.
The cathodes of the lamps VL1 and VL2 approach point a, where they are connected to the zener diodes VD1 and VD2, which create a bias voltage by two separate sections of the mounting wire: ab and ac. This is necessary, otherwise you cannot get rid of self-excitation. Resistors R6...R10 also serve to suppress self-excitation of the power amplifier.
The power amplifier operates in class AB1. The quiescent current of the lamps, equal to 100...120 mA, is obtained automatically, you just need to select the zener diodes in the cathode circuit so that they have a positive voltage of about 18...20 V relative to the chassis.
The input low-pass filter must be adjusted, if necessary, on the 28 MHz range, focusing on the minimum SWR in the cable connecting the transceiver to the PA. The setting is made by selecting the inductance L6 and the input capacitances of the low-pass filter. In addition, the “Antennoscope” from K. Rothhammel is very suitable for this purpose, plus any high-frequency generator, for example, G4-18A. The value of SWR in this case is found as the ratio of resistances. Setting up the driver is quite simple and comes down to setting the quiescent current of transistors VT1 and VT2 to about 80...90 Ma by selecting resistors R11 and R13.
The P-circuit should first be set up in a “cold” way; the diagram of the stand is shown in Fig. 3. You should not, as some authors recommend, disconnect the lamps and anode choke from the circuit and replace them with an equivalent capacity. Firstly, it is difficult to accurately measure these capacitances, and not everyone has a capacitance meter, and secondly, the anode choke in the parallel power circuit is connected precisely in parallel with the P-circuit coils (via blocking capacitors C17 and C18). Consequently, a loop, reactive current flows through it, depending on the magnitude of the alternating voltage at the anode of the lamp and the inductance of the inductor itself. As is known, when two or several self-induction coils are connected in parallel, their total, total inductance value decreases and becomes less than the value of any of the parallel-connected coils. It is clear that the greatest decrease in the size of the self-induction coil of the P-circuit will occur in the range of 1.8 MHz. In the 28 MHz range, the effect of the anode choke on reducing the inductance of the loop coil is insignificant, is within the error limits of the measuring instruments, and can be neglected. When making coils exactly as described, tuning comes down to checking for resonance in the middle of the ranges. For this purpose, a heterodyne resonance indicator (HIR) is suitable, which, despite its simplicity, is a universal high-frequency device and is completely undeservedly forgotten in our time. Do not forget about the neon light bulb, which, when attached to a long fiberglass shelf, is an excellent peak indicator of high-frequency voltage and allows you to accurately determine the moment of fine-tuning the P-circuit to resonance, or, for example, the presence of self-excitation. By the color of its glow, one can approximately determine the frequency of self-excitation: at the operating frequency, the glow of a neon light bulb has a yellowish-violet color, and when self-excited on VHF, its glow takes on a bluish tint.
The anode current of the lamps with a detuned P circuit should be about 300 mA. The anode current of the lamps with a configured P-circuit should not be less than 240 ... 250 mA. That is, the “dip” of the anode current in the process of setting up the P-circuit should not exceed 60 mA, since in this case the anode current is redistributed “in favor” of the current of the screen grids of the lamps. Consequently, a larger current of the screen grids will cause their power overload , and the lamps will go into overvoltage mode, which is undesirable, since the linearity of the RA will deteriorate..
A well-tuned power amplifier does not interfere with television and other household equipment. It is quite possible to use GU-19 lamps, which are slightly more linear and less prone to self-excitation.
Literature:
1. Cascode wideband power amplifier. Radio No. 3, 1978.
2. L. Evteeva. "Cold" setting of the transmitter P-circuit. Radio, 1981, No. 10.
Alexander Kuzmenko (RV4LK).
In amateur design, a “hybrid” PA circuit with a transistor in the cathode circuit of the output lamp has become widely used. In addition to the undoubted advantages, this “hybrid” also has disadvantages, the main one of which is low reliability. Powering the transistor from a common high-voltage source with the lamp carries the danger of breakdown of the transistor, as many radio amateurs have seen. In addition, it is difficult to optimize the transistor mode, because its collector current is rigidly connected to the current through the lamp, the load resistance is predetermined and not optimal, and popular tetrodes with beam-forming plates cannot be used in the circuit.
These disadvantages are absent in the described amplifier, the circuit of which is shown in Figure 1. It consists of a broadband pre-amplifier on VT1, VT2, VT3 and a final stage on a GU-19 lamp with a grounded cathode and a P-circuit system at the output. At UBX -0.5V in the range of 1.5 ... 30 MHz, the anode current of the lamp (with a detuned circuit) is 140 ... 160 mA with a smooth increase at high frequencies due to frequency-dependent circuits R7C4, R13C10, R14R15C12. With an optimal setting of the P-circuit, the anode current of the lamp is about 120 mA, the output power at an anode voltage of 530V was 40 W at low frequency. bands and 25 W at 29 MHz. The measured value of third-order intermodulation distortion is better than -33 dB.
Fig.1.
Transistor part of the amplifier
It is powered by a separate ungrounded rectifier with an output voltage of 36V and consumes no more than 130 mA. Using the zener diode VD1 and resistor R17, an artificial “middle” point is created, voltages +6.8V and -29V relative to ground. It is possible to supply power from separate sources of +(6...9) V and -30V, in this case the requirements for the magnitude of supply voltage ripple are more stringent./off) was carried out using contacts To the relay RX/TX transceiver. When the relay contacts open (transmit), transistors VT1, VT2 go into operating mode. In this case, the bias voltage of the lamp can be changed using resistor R3; the most linear mode according to the results of measurements with a two-tone signal was Ec 1 = -20V and quiescent current of the lamp Ia 0 n = 50 mA. When the relay contacts are closed (receive), the VT3 transistor and the lamp are practically locked. The input impedance of the amplifier is determined by the value of R4 and can be in the range of 50...150 Ohms.Tube cascade
The appearance of grid currents, taking into account the small resistance value in the grid circuit R16 = 120 Ohm, will slightly deteriorate the linearity, but in no case should the “swing” be allowed to lead to VT3 going into saturation with SSB. With CW, it is possible to increase Ia0 to 170 mA without unpleasant consequences. The applied VT3 mode is economical and provides significant margins in relation to the maximum permissible parameters.
The described circuit of the transistor part can be used with other lamps, for example, GU-70B, with a corresponding change in the voltage of the power supplies and setting the lamp modes.
Construction and details
The block dimensions are 95x80x300 mm, the lamp is located horizontally. The transistor preamplifier is mounted on a radiator measuring 60
x 60x25 mm, located in close proximity to the lamp panel. The radiator forms part of the rear wall of the block; connector XS1 and the initial bias setting resistor R3 are mounted directly on it. Transistors VT1 and VT2 are tightly inserted into the holes in the body of the radiator, their terminals are used as reference points for mounting parts.Trimmer KPV-150 (S) was used as variable capacitors of the P-circuit
= 5...150 pF) at the input, at the output - a dual small-sized solid dielectric from an old pocket receiver with a total capacity of about 800 pF. The range switch uses 11P1N ceramic boards.Inductance data:
Choke L3 -165 turns of PELSHO 0.27, frame diameter 13 mm, winding length 55 mm, first 15 turns in a row, the rest close together. Additional capacitors in the output circuit are type KTK-3 and KSO-2, S14 and S15 - KSO-2, S19 - type K15-5 at 3 kV. The group of capacitors C23, C25, C27 have a total capacitance of 350 pF. The ranges 10, 12, 15 and 17 m overlap in the position of the switch S1 “10” or “15”, 20 and 30 m - in the position “20”, ranges 40, 80 and 160 m - each in its own position.
The described amplifier has been in operation since 1989. During this period, VD1 (KS168A) had to be replaced once; there were no other failures.
Measurement
3rd order distortion was carried out using a standard method. 2 GSS were used, the signals of which were fed through a adding device to the XS1 input, the equivalent of an E9-1 antenna with a control tap, 10 and 20 dB attenuators, a V7-37 voltmeter and a transceiver as a measuring receiver. The GOS frequencies were set within the range of 14 MHz with a difference of 10 kHz. The output level of each GSS was set in turn so as to obtain a voltage DH at the load corresponding to an output power of 40 W (at the same time Ia 0 = 120 mA).Then the level of each of the generators was reduced by approximately 6 dB in such a way that when they were turned on together, the voltage across the load remained equal to 11N (at the same time Ia
0 - 90mA). The receiver controlled the level of one of the combination frequencies of the type (2f1 - f2) and by adjusting R3, a mode was set that gave a noticeable minimum of distortion. To eliminate the error of the S-meter, the noted levels of the main signal and combination frequencies were then checked using the GSS.Ernst Gutkin (UT1MA)
The material was prepared by Yu. Pogreban (UA9XEX).
For the output stage of radio stations of the 2nd category, the transmitting power of which on all amateur HF bands, with the exception of 160 m (operation on the 30 m band for these radio stations is not allowed), can be equal to 50 W and which can have SSB mode, it is recommended to use the following devices: transistors - KP904, KT909B, G (2 pcs.), KT922V, D (2 pcs.), KT926, KT927, KT930-KT932 (2 pcs.), KKT935, KT945, KT958, KT960; lamps - GI-30, GMI-10, GU-19, GU-29, GU-42, GU-50, 6P20S, 6P45S.
In Fig. Figure 2.39 shows a diagram of a power amplifier for a radio station of the 2nd category, in which a 6P45S lamp is used, connected according to a circuit with a grounded grid.
The grounded grid circuit allows the use of tubes that are not specifically designed for this purpose in high-frequency power amplifiers. The circuit under consideration uses a powerful beam tetrode, usually used in horizontal scanning devices of televisions. Unlike other similar domestic radio tubes, 6P45S has a separate output from the beam-forming plates, this determines the possibility of its successful use in devices with a grounded grid (if the beam-forming plates are connected inside the lamp to the cathode, then the cathode-anode capacity turns out to be unacceptably large). Typically, an amplifier based on a circuit with a grounded grid for its excitation requires a power equal to 10.. 20% of the output. To obtain a power gain of about 50, a field-effect transistor VT2 is connected to the cathode circuit VL1. This will make it possible to use the exciters discussed above with an output power of about 1 W with a power amplifier (Fig. 2.39). Stable operation of VT2 and the entire amplifier is ensured by the inclusion of a low-resistance resistor R15 in the VT2 gate circuit, which is the exciter load. Cathode VL1 is isolated from the high-frequency supply circuit by inductor L5-L6, and is connected to the housing only through VT2 for direct current. The transition from reception to transmission is controlled by shorting the XS2 connector to the body. While this circuit is open, VT1 is open and its collector current causes the HF coaxial relay K1 to operate. In this case, the antenna is disconnected from the power amplifier and connected to the receiver input. At the same time, open VT1 reduces the voltage on the control grid VL1 to fractions of a volt, and the positive voltage on the cathode of VL1, created by the voltage divider R6, VT2, is sufficient to close VL1.
When the control circuit is closed through XS2, transistor VT1 closes, relay winding K1 is de-energized and the antenna switches from the receiver input to the power amplifier output. At the same time, 24 V is supplied to the control grid VL1 through the relay coil K1 and VL1 opens. The current through VL1 is set to close to 50 mA by selecting resistor R10.
When approximately 1 W of excitation is applied to XS5, the current through VL1 increases to 200 mA.
The anode circuit VL1 includes circuit R9, L2, eliminating the possibility of self-excitation of the VHF cascade.
The VL1 load is a P-circuit, the variable capacitors of which are two identical double blocks of capacitors from a broadcast receiver with a gap between the plates of at least 0.3 mm. The first block of capacitors C10 is isolated by its housing from the chassis, one of the stators is connected to the chassis, and the other to L3 so that capacitors C10.1 and C10.2 are connected in series, forming a tuning capacitor with a maximum capacitance of 225 pF and an equivalent gap of at least 0.6 mm. The coupling capacitor is formed by C11.1 and C11.2 connected in parallel. The power amplifier is powered by two rectifiers. The first rectifier, assembled on diodes VD1-VD4, provides a voltage of +500 V to power the anode VL1 and +250 V to power the shielding grid of this lamp. In this rectifier, as in the power amplifier (Fig. 2.37), good filtering of the anode supply voltage is not necessary, but the necessary filtering of the shielding mesh power supply is provided.
The second 4-24 V rectifier powers the relay winding and the control circuit for the transition from reception to transmission. The necessary smoothing of the voltage supplied to the control grid VL1 is carried out by filter R5C6.
Inductor L1 is wound on a textolite rod with a diameter of 80 mm using PESHO 0.31 wire. From the end connected to C7, a winding 80 m long is first wound turn to turn, and then another 25 turns are wound in increments of 1 mm. After winding, the choke is covered with a layer of BF-6 glue and dried until it polymerizes. Coil L2 is wound with PEV-2 0.8 wire on a frame, which is a resistor R9 type MLT-1, number of turns 4, coil length 8 mm. For the 10 m range, the L3 coil is used. It contains 4 turns (PEV-2 wire 1.55), the diameter of the turns is 30 mm, the length of the coil is 15 mm. The frame for L3 is not used. Coil L4 is wound on a plastic frame with a diameter of 32 mm, the number of turns is 25, the winding length is 50 mm (PEV-2 wire 1). The taps are made (counting from the end connected to L3) from turns 3,6, 8 and 10. Switch SA2 is a PGK type biscuit switch. The inductor L5-L6 is wound with two PEV-2 1.2 wires in parallel on a ferrite rod from the magnetic antenna of a portable receiver. The rod material can be anything (for example, a rod from a HF antenna or LW and SV antennas). The shape of the rod is round or rectangular. Before winding, the rod must be insulated with varnished cloth. Winding - turn to turn, its length is about 80 mm.
The network transformer must provide on winding II - 2 200 V at a current of up to 0.3 A, on winding III - 20 V at a current of up to 0.3 A, on winding IV - 6.3 V at a current of up to 2.5 A. This transformer is wound on an Ш24 magnetic core, the thickness of the set is 50 mm. Winding I - 990 turns (wire PEV-2 0.49); winding II - 2X900 turns (wire PEV-2 0.29); winding III - 90 turns (wire PEV-2 0.29); winding IV - 30 turns (wire PEV-2 1.2).
The power amplifier is adjusted on each range based on the maximum readings of the voltmeter, which measures the voltage at the output of the amplifier. This voltmeter is formed by a voltage divider R12, R13, a detector on VD6 and a filter C16R14. PA1 is used as a measuring device and is less sensitive than indicated in the diagram.
Condition: used
Availability: in stock
Technical condition: good
Guarantee: seller's warranty
Output power amplifier of a VHF radio transmitter based on a GU-19 lamp. Output power is approximately 40 W. The operating frequency range, judging by the input and output circuits, is amateur radio - at a frequency of 144-146 MHz. It is not possible to check the functionality due to the lack of necessary measuring equipment. The installation of the amplifier is normal, not touched. Everything was normal before. The amplifier has not been turned on or used for a long time. With a normal GU-19 working lamp, the amplifier will work at 100%. Can be paired with a stationary radio transmitter, which is also presented in one of my lots. Sold as is, no returns or claims.
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