Tube HF power amplifier. What should a power amplifier for an amateur HF radio station be like? HF transformers for HF amplifiers for amateur radio operators

tube, transistor

As practice shows, few radio amateurs work QRP, while most sooner or later begin to dream of increasing the transmitter power. That's when and the question arises about preference to a lamp or a transistor. Long-term practice of operating both of them has shown that tube amplifiers are much simpler to manufacture and less critical to operating conditions, and the weight of the anode transformers is practically compensated by the weight of the radiators necessary for cooling powerful transistors, which are more capricious in operation, especially to overloads, so experiments with they are quite expensive. It is easier to make a power supply with a power of 2 kW at 2000 V at a current of 1 A than 20 V at a current of 100 A. The presence of small-sized electrolytic capacitors designed for high voltage and large capacity allows you to create small-sized high-voltage sources for tube amplifiers directly from the network without using power transformers.

The power amplifier is one of the main attributes of a contestant's and DX-man's radio station. Depends on his choice results in competitions and ratings.

HF power amplifiers on tubes, transistor HF power amplifiers

An output amplifier (power amplifier - PA) is an amplifier loaded onto an antenna. The output amplifier consumes most of the power. The operation of the PA mainly determines the energy performance of the entire radio station, so the main requirement for the output stage is to obtain high energy performance. In addition, good filtering of higher harmonics is very important for the output amplifier.

A good modern HF power amplifier is a rather complex and labor-intensive device, as evidenced by world prices for branded PAs, at least in relation to the cost of middle-class transceivers produced by the same companies. This is explained, firstly, by the high cost of the lamps themselves used in the PA, and secondly, also by the high percentage of manual labor in their manufacture.

ACOM-1000

The ACOM 1000 HF power amplifier is one of the most worthy HF power amplifiers in the world. The output power of ACOM 1000 is at least 1000 W on all amateur radio bands from 160 to 6 meters.

Without antenna tuner

The amplifier functions as an antenna tuner with an SWR of up to 3:1, thus allowing you to change antennas faster and use them over a larger frequency band, saving tuning time.

One output tube 4CX800A (GU-74B)

The amplifier uses a high-performance metal-ceramic tetrode produced by the Svetlana plant with an anode dissipation power of 800 W (with forced air cooling and grid control).

Technical characteristics of the ACOM 1000 power amplifier:

Frequency range: all amateur radio bands from 1.8 to 54 MHz; extensions and/or changes upon request.
Output power: 1000 W peak (PEP) or push mode, no operating mode restrictions.
Intermodulation distortion: better than 35 dB below peak rated power.
Hum and Noise: Better than 40 dB below peak rated power.

Harmonic Suppression:

1.8 - 29.7 MHz - better than 50 dB below peak rated power.
50 – 54 MHz - better than 66 dB below peak rated power.

Input and output impedance:

nominal: 50 ohms, unbalanced, UHF connectors (SO239);
input circuit: wideband, SWR less than 1.3:1 in a continuous frequency band of 1.8-54 MHz (no need for tuning and switching);
pass-through SWR less than 1.1:1 in the continuous frequency band 1.8-54 MHz;
Output matching capabilities: better than 3:1 SWR or greater at reduced power levels.

RF gain: 12.5 dB typical, frequency response less than 1 dB (with 50 - 60 W input signal at rated output power).
Supply voltage: 170-264 V (200, 210, 220, 230 and 240 V taps, 100, 110 and 120 V taps on request, with tolerance +10% - 15%), 50-60 Hz, single phase, Consumption 2000 VA at full power.
Meets the safety requirements of EEC countries and the requirements for electromagnetic compatibility parameters, as well as the rules of the US Federal Communications Commission (FCC) (the unit is installed on the 6, 10 and 12 m bands).
Dimensions and weight (in working condition): 422x355x182 mm, 22 kg
Requirements for environmental parameters during operation:
temperature range: 0...+50°С;
relative air humidity: up to 75% at a temperature of +35°C;
altitude: up to 3000 m above sea level, without deterioration of technical parameters.

ACOM-1011

The ACOM 1011 power amplifier is developed on the basis of the well-known ACOM 1010.

The outstanding performance characteristics of the latter have been noted by many radio amateurs around the world.

At the WRTC Championship in Brazil, teams used the ACOM 1010 amplifier and it was recognized as the most optimal for both stationary use and DXpeditions.

The main differences between the two amplifiers:

The ACOM 1011 uses two 4CX250B tubes, currently produced by many of the most renowned tube manufacturers, and provides the same power output as a single GU-74B tube.
The lamp warm-up time has been reduced to 30 seconds.
The tube panels are custom made by ACOM and designed specifically for installation in this amplifier.
The ACOM 1011 uses a new fan designed and manufactured specifically for ACOM based on the well-known and proven fans used in the ACOM 1000 and ACOM 2000 models. It uses similar components, which provides better cooling and quieter operation of the amplifier overall compared to with ACOM 1010.
ACOM 1011 has some differences both outside and inside. The more durable metal construction improves its performance during transport and DXpedition work.

ACOM-2000

Automatic power amplifier ACOM 2000A – HF amplifier with the most advanced technical characteristics in the world of amplifiers produced for amateur radio applications. The ACOM 2000A is the first amateur radio power amplifier to combine a fully automated setup process with sophisticated digital control capabilities. The new amplifier has an improved design and produces maximum permitted power in all radiation modes and operates on all amateur radio HF bands.

Cutting-edge technology improves classic amplifier design

Fully automatic setup

The automatic tuning functions of the ACOM 2000A amplifier are a real breakthrough in the field of HF power amplifier design. There is no need to think about using an antenna tuner with an SWR of up to 3:1 (2:1 in the 160 meter range). The process of matching the actual characteristic impedance with the optimal lamp load is fully automated. This process lasts no more than one second and does not require much experience.

QSK – full duplex mode

Full duplex operation (QSK) is based on a built-in vacuum relay. The sequence of switching from transmitting to receiving mode is provided by a dedicated microprocessor.

Remote control

Only the remote control should be located near the operator. The amplifier itself can be placed up to 3 m (10 ft) away. GLE functions include: amplifier status on the LCD display, control of all functions, measurement and/or monitoring of the twenty most important amplifier parameters, operational Technical information, troubleshooting suggestions, recording the number of working hours, password protection.

Protection

Continuous monitoring and protection of such parameters and functions as:
all lamp voltages and currents,
supply voltages,
overheat,
pumping based on input signal,
insufficient amount of cooling air,
internal and external RF sparking (in amplifier, antenna switch, tuner or antennas),
sequence of switching from transmit to receive T/R,
switching the antenna relay during transmission,
quality of matching with the antenna,
reflected power level,
saved data,
inrush current of the supply voltage network,
Lid lock for operator safety.

Technical characteristics of the ACOM 2000A power amplifier:

Output power: 1500-2000 W in push mode or SSB mode - no time limit. Continuous radiation mode - 1500 W output power - no time limit when using an additional cooling fan.
Frequency range: all amateur radio bands from 1.8 to 24.5 MHz. 28 MHz band only with modifications for licensed radio amateurs.
Reranging/Tuning: Initial output matching occurs in less than 3 seconds (typically 0.5 seconds). The process of adjusting to previously agreed upon settings/band switching takes less than 0.2 seconds to move to another part of the same range, and less than 1 second when moving to another range.
Non-volatile storage device (memory) for configuring up to 10 antennas per frequency segment.
Drive signal power: typically 50 Watts with 1500 Watts output power.
Input impedance: nominal 50 Ohm. SWR<1.5:1.
Output tolerance: up to 3:1 VSWR (2:1 at 160 meters) at full output power before high VSWR protection circuit is activated. Higher SWR values are matched at lower output power.
Harmonic Content: At least 50 dB below peak at 1500 Watts.
Intermodulation Interference: At least 35 dB below peak at 1500 Watts.
T/R Switching and Keying: Vacuum Relay: Capable of Full Duplex (QSK) operation.
Output tubes and circuits: tetrodes 4CX800A/GU74B (2 pcs.), resistive grid, PI-L output circuit with negative RF feedback. Adjustable screen grid voltage.
Automatic Level Control (ALC): Negative grid voltage control, -11V maximum, rear panel adjustable.
The remote control unit provides monitoring of all operating parameters of the amplifier.
Protection: limiting the current of the control and screen grid, due to power surges (the possibility of smooth switching is provided), shutdown when the reflected power value is exceeded, when sparking in the RF circuit, access is password protected if necessary, correction of alternating switching between transmit and receive modes (T/R) , removal of lamp cooling air, blocking and grounding device for the high voltage circuit when opening the cover.
Fault diagnosis: remote control display, plus indicators, plus information device "INFO Box" for the last 12 events. Computer interface (RS-232), plus remote telephone polling line function.
Cooling: Full forced airflow inside the case. Rubber insulated fan.
Transformer: 3.5 KVA with Unisil-Ha strip core.
Power supply requirements: 100/120/200/220/240 Volts AC. 50-60 Hertz. 3500 VA, single phase, at full power.
Overall dimensions: HF unit: length 440 mm, height 180 mm, depth 450 mm, remote control unit: length 135 mm, height 25 mm, depth 170 mm
Transported in two cardboard boxes, total weight 36 kg.
There are no controls on the HF unit, with the exception of the ON/OFF switch.

Alpha-9500

The Alpha-9500 is no ordinary linear amplifier, but the culmination of over 40 years of design and engineering.

Alpha-9500 is an advanced technology, auto-tuning linear amplifier easily provides 1500W of output power with a minimum input power of only 45W.

SPECIFICATIONS:

All amateur bands from 1.8 - 29.7 MHz

Output power: 1500 W minimum, on all bands and types of radiation
3rd order IM:< -30 дБн
SWR allowed: 3:1
Power input: 45-60 W to achieve rated full power
Lamp: one 3CX1500/8877 - high power and performance triode with a dissipation power of 1500 W provides the declared power in all frequency ranges, in all modes, in all duty cycles.
Cooling: Forced air from two fans
Antenna Outputs: Comes standard with 4 SO-239 connectors, but can be changed to N type on the rear panel by removing 4 screws.
Antenna selection: internal antenna 4-port switch with 1 or 2 outputs per band
Calibrated Wattmeter: The Bruene Wattmeter allows you to simultaneously measure forward and reverse power and display this information in an easy-to-read front panel bar graph. It also uses the information to simultaneously control the amplifier's gains.
Protection mechanisms: high-voltage blocking and power supply blocking.
Bypass Mode: There are two "ON" power switches on the front panel of the ALPHA-9500.
"ON1" activates the Wattmeter and antenna switch without turning off the power to the amplifier itself, and sets the amplifier to bypass mode.
The amplifier itself is turned on with the "ON2" button.
Input: Comes standard with SO-239 BIRD connector, but can be changed to BIRD N type
Tuning/switching ranges: Automatic, plus manual control
Power: 100, 120, 200, 220, 240 VAC, 50/60 Hz, automatic selection. At 240 VAC, the amplifier draws up to 20 amps.
Interface: serial port and USB. Full remote control function.
Protection: Protection against all common faults.
Display: The display shows histograms of power, SWR, grid current, plate current, plate voltage and gain - all at once. The digital instrument panel can display input power, plate current, plate voltage, grid current, SWR, filament voltage and PEP output.
Tx/Rx switching: two Gigavac proprietary vacuum relays allow QSK to QRO operation.
Output power: 1500 W.
Weight: 95 lbs
Dimensions: 17.5"W X 7.5"H X 19.75"D

Ameritron AL-1500

Ameritron AL-1500 is one of the most powerful linear amplifiers, covering all HF and WARC ranges.

It uses a manually tuned amplifier, which is designed around a single 3CX1500/8877 ceramic tube and has an efficiency of at least 62-65%.

With an input power of 65 W, it produces the legal maximum power with a large margin, up to 2500 watts.

The amplifier features a Hypersil ® transformer, dual backlit instruments, adjustable ALC, delay time adjustment, current protection and more.

Price (approximately in the Russian Federation) = $3650

Ameritron AL-572X

The Ameritron AL-572 amplifier is made using four 572B tubes using a common grid design. The Ameritron AL-572 amplifier uses tube capacitance neutralization, which improves performance and stability in the HF ranges. The lamps are installed vertically, which significantly reduces the risk of interelectrode short circuits

To match the input of the Ameritron AL-572 amplifier with the output of the transmitter, separate P-circuits are installed at the input for each of the operating ranges. The use of a tuned input equalizes the load on the output stage of the transceiver and allows you to get an SWR close to 1 on all bands. Additional adjustment of the circuits is possible through the holes in the rear panel of the amplifier.

The anode power supply is assembled using a voltage doubling transformer circuit and uses high-capacity electrolytic capacitors. The anode transformer is wound on a prefabricated steel core made of plates coated with high temperature resistant silicone coating, providing high power density with low weight. The anode no-load voltage is 2900 volts, at full load about 2500 volts. To reduce the temperature inside the Ameritron AL-572 case, a low-speed computer-type fan is used to circulate air at a low noise level.

Details of the Ameritron AL-572 output circuit (frameless coils made of thick wire, anode capacitor with ceramic insulators and a large gap between the plates, range switch on a ceramic dielectric) ensure reliable operation and high efficiency of the oscillatory system. The handles of variable capacitors are equipped with verniers with retardation and rotor position indication.

The Ameritron AL-572 amplifier also has an ALC system, a switch for operating and bypass modes, an indication of transmission operation and instruments for measuring the voltage of the anode power source / anode current and the value of the grid current. Both measuring instruments are backlit. For QSK operation, it is possible to install an additional QSK-5 module.

Price (approximately in the Russian Federation) = $2240

Specifications

Peak output power: SSB 1300 Watts, CW 1000 Watts
Excitation power from the transceiver 50-70 Watts
Lamps: 4 572B lamps with neutralization in inclusion with a common grid
Power supply: mains 220 volts
Dimensions: 210x370x394 mm
Weight: 18 kg
Manufacture: USA

Ameritron AL-800X

Tube power amplifier for HF transceivers

Operating frequency range: from 1 to 30 MHz

Output power: 1250 Watts (peak)

Built on a 3CX800A7 tube

Price (approximately in the Russian Federation) = $2900

Ameritron AL-80BX

The Ameritron AL-80B linear power amplifier is made using a 3-500Z tube using a common grid design. The lamp is installed vertically, which significantly reduces the risk of interelectrode short circuits.

To match the input of the Ameritron AL-80B amplifier with the output of the transmitter, separate P-circuits are installed at the input for each of the operating ranges. The use of a tuned input equalizes the load on the output stage of the transceiver and allows you to get an SWR close to 1 on all bands. Additional adjustment of the circuits is possible through the holes in the rear panel of the amplifier.

The anode power supply of the Ameritron AL-80B amplifier is assembled using a transformer circuit with voltage doubling and uses high-capacity electrolytic capacitors. The anode transformer is wound on a prefabricated steel core made of plates coated with high temperature resistant silicone coating, providing high power density with low weight. The anode no-load voltage is 3100 volts, at full load about 2700 volts. To reduce the temperature inside the case, a low-speed computer-type fan is used, which ensures air circulation at a low noise level.

The details of the output circuit of the Ameritron AL-80B amplifier (frameless coils made of thick wire, an anode capacitor with ceramic insulators and a large gap between the plates, a range switch on a ceramic dielectric) ensure reliable operation and high efficiency of the oscillatory system. The handles of variable capacitors are equipped with verniers with retardation and rotor position indication.

The Ameritron AL-80B amplifier also has an ALC system, a switch for operating and bypass modes, an indication of transmission operation and instruments for measuring the voltage of the anode power supply/anode current and the magnitude of the grid current. For QSK operation, it is possible to install an additional QSK-5 module.

Price (approximately in the Russian Federation) = $1990

Specifications

Operating ranges: 10-160 meters, including WARC
Peak output power: SSB 1000 Watts, CW 800 Watts
Excitation power from the transceiver 85-100 Watts
Lamps: 3-500Z lamp with neutralization in inclusion with a common grid
Input and output impedance: 50 ohms
Power supply: mains 220 volts
Dimensions: 210x370x394 mm
Weight: 22 kg
Manufacture: USA

Ameritron AL-811

The Ameritron AL-811 HX linear power amplifier is made using four 811A lamps (a complete analogue is the G-811 lamp) according to a circuit with a common grid. The lamps are installed vertically, which significantly reduces the risk of interelectrode short circuits.

To match the amplifier input with the transmitter output, separate P-circuits are installed at the input for each of the operating ranges. The use of a tuned input equalizes the load on the output stage of the transceiver and allows you to get an SWR close to 1 on all bands. Additional adjustment of the circuits is possible through the holes in the rear panel of the amplifier.

The anode power source is assembled using a transformer bridge circuit and uses high-capacity electrolytic capacitors. The anode transformer is wound on a prefabricated steel core made of plates with a high-temperature resistant silicone coating, providing high power density with low weight (8 kg). The anode no-load voltage is 1700 volts, at full load about 1500 volts. To reduce the temperature inside the case, a low-speed computer-type fan is used, providing air circulation at a low noise level.

The amplifier also has an ALC system, a switch for operating and bypass modes, an indication of transmission operation and instruments for measuring the voltage of the anode power source/anode current and the value of the grid current. For QSK operation, it is possible to install an additional QSK-5 module.

Price (approximately in the Russian Federation) = $1200

Specifications

Peak output power - in SSB mode 800 Watt, in CW mode 600 Watt (excitation power from the transceiver 50-70 Watt)
Input and output impedance - 50 Ohm
Operating ranges - 10-160 meters, including WARC
4 811A lamps included with a common grid
Adjustable ALC output
Supply voltage 240 volts, commutable
taps for mains power 100/110/120/210/220/230 volts
Weight 15 kg

Ameritron AL-82X

The Ameritron AL-82X linear power amplifier is made using two 3-500Z tubes using a common grid design. The Ameritron AL-82 amplifier uses tube capacitance neutralization, which improves performance and stability in the HF ranges. The tubes in the Ameritron AL-82 amplifier are mounted vertically, which significantly reduces the risk of interelectrode short circuits.

To match the input of the Ameritron AL-82X amplifier with the output of the transmitter, separate P-circuits are installed at the input for each of the operating ranges. The use of a tuned input of the Ameritron AL-82 amplifier equalizes the load on the output stage of the transceiver and allows you to get an SWR close to 1 on all bands. Additional adjustment of the circuits is possible through the holes in the rear panel of the amplifier.

The anode power supply of the Ameritron AL-82 amplifier is assembled using a voltage-doubling transformer circuit and uses high-capacity electrolytic capacitors. The anode transformer is wound on a prefabricated steel core made of plates coated with high temperature resistant silicone coating, providing high power density with low weight. The anode no-load voltage is 3800 volts, at full load about 3300 volts. To reduce the temperature inside the Ameritron AL-82 amplifier, a low-speed computer-type fan is used to circulate air at a low noise level.

Details of the output circuit (frameless coils made of thick wire, an anode capacitor with ceramic insulators and a large gap between the plates, a range switch on a ceramic dielectric) ensure reliable operation and high efficiency of the oscillatory system. The handles of variable capacitors are equipped with verniers with retardation and rotor position indication.

The Ameritron AL-82X amplifier also has an ALC system, a switch for operating and bypass modes, an indication of transmission operation and instruments for measuring the voltage of the anode power source/anode current and the value of the grid current. Both measuring instruments are backlit. For QSK operation, it is possible to install an additional QSK-5 module.

Price (approximately in the Russian Federation) = $3000

Ameritron AL-82X Amplifier Specifications

Operating ranges 10-160 meters, including WARC
Peak output power: SSB 1800 Watts, CW 1500 Watts
Excitation power from the transceiver 100 Watt
Lamps: 2 lamps 3-500Z lamps with neutralization in inclusion with a common grid
Input and output impedance 50 Ohm
Power supply 220 volts
Dimensions 250x432x470 mm
Weight 35 kg
Made in USA

Ameritron ALS-1300

Ameritron offers its new solid-state amplifier ALS-1300.

The amplifier output power is 1200W in the frequency range 1.5 - 22 MHz.

The amplifier does not require time to rebuild; 8 pcs MRF-150 FETs are used as output transistors.

The amplifier uses a fan whose rotation speed is controlled by temperature sensors to ensure minimal noise.

The ALS-500RC remote control can be used with the ALS-1300 amplifier

Ameritron ALS-500M

The amplifier uses four powerful 2SC2879 bipolar transistors

The amplifier is made without the use of vacuum tubes, so it does not require preheating

The amplifier does not need to be adjusted. Switching ranges from 1.5 to 29 MHz is carried out with one knob

The amplifier monitors the load resistance and if it deviates more than the permissible norm, “bypass” is activated

The amplifier has a built-in current consumption indicator that allows you to monitor the collector current of the output transistors

To bypass the amplifier, you do not need to disconnect it. You just need to switch it to the “off” position

The weight of the amplifier is only 3.9 kg with dimensions of 360x90x230 mm

When operating the amplifier in stationary mode, it is recommended to use a power source with an output voltage of 13.8 V and an operating current of at least 80 A.

Price (approximately in the Russian Federation) = $1050

Technical characteristics of the ASL-500M power amplifier:

Frequency range: 1.5 - 30 MHz
Output power: 500 W peak (PEP) or 400 W in CW mode
Drive signal power: typically 60-70 W
Supply voltage: 13.8 V, consumption 80 A
Harmonic Rejection: 1.8 – 8 MHz – better than 60 dB below peak rated power, 9 – 30 MHz – better than 70 dB below peak rated power
When operating the amplifier in stationary mode, it is recommended to use a power source with a maximum output current of at least 80A.

Ameritron ALS-600

No setup, no fuss, no worry - just plug and play

Includes 600 W output power, continuous frequency range 1.5-22 MHz, instantaneous band switching, no warm-up time, no child-hazardous lamps, maximum SWR protection, completely silent, very compact.

The revolutionary AMERITRON ALS-600 amplifier is the only linear amplifier in ham radio that uses four reliable RF power TMOS FETs - delivering unsurpassed solid-state quality and requiring no tuning. Price includes non-tuned FET amplifier and 120/220 VAC, 50/60 Hz power supply for home use.

You get instant range switching, no setup required, no warm-up time, no fuss! The ALS-600 amplifier provides a maximum 600 W envelope output power and 500 W CW power over a continuous frequency range of 1.5 to 22 MHz

The ALS-600 amplifier is completely silent. The low-speed, low-volume fan is so silent that it is difficult to detect its presence, unlike the noisy blowers found in other amplifiers. The ALS-600 amplifier has small dimensions: 152x241x305 mm - it takes up less space than your radio! Weighs only 5.7 kg.

The two-pointer SWR and power meter with backlight allows you to read the values of SWR, maximum power of the incident and reflected waves simultaneously. The Operate/Standby switch allows you to operate in low power mode, but you can instantly switch to full power mode if needed.

You get the ability to control the ALC system from the front panel! This unique AMERITRON system allows you to adjust the power output on a convenient front panel indicator. Additionally, you get LED indicators for transmit, ALC and SWR on the front panel. The 12 VDC output jack allows you to power low-current accessories. Enjoy 600 watts of non-tuning solid state amplifier power. A pair of RJ45 remote control interface jacks on this amplifier allow you to control the ALS-600 amplifier either manually using the ALS-500RC compact remote control unit, or automatically using the ARI-500 automatic band selector. The Automatic Band Switch reads band data from your transceiver and automatically changes the ALS-600 amplifier's bands when the bands on the transceiver change.

Price (approximately in the Russian Federation) = $1780

Expert 1K-FA

Fully automatic 1KW transistor linear amplifier.

Built-in power supply and automatic antenna tuner. Dimensions: 28x32x14 cm (including connection connectors).

Weight about 20 kg.

The Expert 1K-FA amplifier uses two processors, one of which is designed to automatically adjust the output P-circuit. (System S.A.T.s) More than 13,000 software elements provide a unique set of technical characteristics not found in other models.

Possibility of easy connection to all models of Icom, Yaesu, Kenwood transceivers, automatic antenna tuner, control of antenna characteristics, immediate broadcasting. Similar results when working with models from other companies and homemade equipment. The operator's functions are limited to rotating the frequency control knob in the transceiver.

From 1.8 MHz to 50 MHz including WARC bands. Fully transistor design. 1 kW PEP in SSB mode (nameplate value). 900 W in CW mode (rated value) 700 W PEP in the 50 MHz band (rated value).

Automatic selection of full/half power by operator command in CW and SSB modes, for digital types of operation and providing automatic amplifier protection. Does not require time to warm up.

The amplification elements are not subject to aging (CMOS transistors are used). Built-in automatic antenna tuner. It is possible to match antennas up to SWR values of 3:1 on HF, and 2.5:1 on 6 meters. Switching up to 4 antennas (SO239 connectors). Switching bands, antennas and all adjustments are carried out in 10 milliseconds. When working only from the transceiver, adjustments, switching of bands and antennas are carried out in the “standby” mode. Availability of two entrances. SO 239 connectors are used.

Drive power 20 W.

Continuous monitoring of temperature, overcurrent and voltage, SWR level, reflected power level, maximum RF tuner voltage, input power “pumping”, imbalance of amplifier stages. Full duplex mode (QSK). Low noise operation. The amplifier and transceiver can be turned on and off independently. The large LCD display displays a large amount of information.

Connection via RS 232 port for control via PC. For ease of carrying, the amplifier fits into a small bag. Possible to work on field days and DX expeditions.

BLA 1000

RM BLA-1000 is a new transistor amplifier, with an output power of up to 1000W, which implements all the most advanced achievements in amplifier design. The output stage of the amplifier is made of two super-power field-effect (MOSFET) transistors MRF-157. A 2-cycle bridge amplification circuit (Push-Pull type), operating in AB2 mode, provides high gain and good amplifier efficiency while maintaining high linearity.

For the convenience of covering all operating ranges, there are 2 antenna ports on the rear panel of the amplifier. For example, you can connect high-frequency range antennas to one port, and low-frequency range antennas to the second.

To control the linearity of the amplifier, there is an ALC input on the rear panel. The possibility of both automatic control of the ALC level and from the transceiver has been implemented. ALC parameters can be adjusted manually using 2 resistors. The release time of the transmit relay (RX-delay) can be adjusted in the range of 0...2.5 seconds in steps of 10 ms.

Switching the “Receive/Transmit” mode can be done either from the transceiver or automatically (Int. VOX). For this purpose, there is an RC connector - “PTT” on the rear panel of the amplifier.

The amplifier is powered by its built-in switching power supply. The amplifier's high output power is obtained by feeding the transistors with high voltage - 48 Volts. In this case, the current consumption at the signal peak can reach 50 Amperes.

One of the interesting features of this amplifier is its ability to operate in fully automatic mode. In this mode, you do not need to switch not only the “Receive/Transmit” mode, but also the operating range of the amplifier. The frequency meter built into the microprocessor will automatically determine the transmission frequency and select the desired low-pass filter. This function will be especially useful for using the amplifier in “unattended areas” or “enclosed spaces” of industrial radio communication structures.

Price (approximately in the Russian Federation) = $4590

Technical characteristics of the power amplifier RM BLA-1000

Frequency range 1.5-30 and 48-55 MHz
Supply voltage 220-240 Volts; 15.5 A
Input power 10-100 Watt
Output power 1000 Watt
Impedance Input/Output 50 Ohm
Overall dimensions 495 x 230 x 462 mm
Weight 30 kg

BLA 350

New, inexpensive amplifier RM BLA-350. An ideal solution for a beginner or intermediate radio amateur who has decided to amplify the signal of his transceiver or protect the output stage for little money. Due to the built-in powerful power supply, the amplifier takes up little space on the table.

The output stage of the amplifier is made of two powerful field-effect (MOSFET) transistors SD2941. A 2-cycle bridge amplification circuit (Push-Pull type), operating in AB2 mode, provides high gain and good amplifier efficiency while maintaining high linearity. Additional purity of the output signal is provided by 7 low-pass filters of the 7th order, which is an important parameter for basic amplifiers.

Thanks to microprocessor control, the control of the amplifier operating modes is fully automated and temperature, SWR and input power control is implemented. Flexible configuration of protection and alarm parameters is possible when threshold values are exceeded.

Switching of the “Reception/Transmission” mode can be controlled either from the transceiver or automatically (Int. VOX). For this purpose, there is an RC connector - “PTT” on the rear panel of the amplifier.

One of the interesting features of this amplifier is its ability to operate in fully automatic mode. In this mode, you do not need to switch not only the “Reception/Transmission” mode, but also the operating range of the amplifier. The frequency meter built into the microprocessor will automatically determine the transmission frequency and select the desired low-pass filter. This function will be especially useful for using the amplifier in “unattended areas” or “enclosed spaces” of industrial radio communication structures.

Price (approximately in the Russian Federation) = $1090

Technical characteristics of the power amplifier RM BLA-350

Frequency range 1.5-30 MHz (Including WARC bands)
Modulation types AM/FM/SSB/CW/DIGI
Supply voltage 220-240 Volts; 8 A
Input power 1-10 Watt
Output power 350 Watt
Impedance Input/Output 50 Ohm
Overall dimensions 155 x 355 x 270 mm
Weight 13 kg

Elecraft KPA-500

The power amplifier is designed to operate on all amateur radio HF bands from 160 to 6 meters (including WARC bands) in all operating modes. The KPA-500 automatically tunes to your transceiver's frequency.

An all-solid-state amplifier with a power of 500 W on powerful FET transistors, has the same dimensions as the Elecraft K3 transceiver and fits perfectly into the line of devices of this company.

The amplifier has an alphanumeric display, a bright LED indicator and a reliable, powerful built-in power supply. The device works with any transceiver that uses a grounded PTT output. When pumping or increasing the SWR, the power is automatically reduced by 2.5 dB, and when the problem is eliminated, it returns to the nominal value.

The amplifier provides ultra-fast, silent QSK using a high-power PIN diode switch. The device has a six-speed temperature-controlled fan. When using the optional KPAK3AUX cable, enhanced integration with the K3 transceiver is provided:

manual control buttons on the KRA500 panel control the ranges and drive level on the K3;
data on switching ranges is transmitted from K3 before the start of transmission;
PTT is transmitted via cable, no separate control is required;
K3 detects the current state of the amplifier and adjusts the drive level according to one of two memory states on each band.

When the Internet is connected, the presence of new firmware versions is automatically detected from the company server via the RS232 port.

HLA-150

Price (approximately in the Russian Federation) = $520

Input power: 1 - 8 W.
Output Power: 150W CW or 200W PEP in SSB.
Supply voltage: 13.8 V.
Maximum current consumption: up to 24 A.
Dimensions: 170x225x62 mm, weight 1.8 kg.

HLA-300

The amplifier has microprocessor control, a frequency range of 1.5-30 MHz, LED indicators of output power and operating range, automatic TX/RX switching. Band switching can be done automatically or manually. The amplifier has band filters on the output that are switched manually when the range changes.

In the event of a malfunction of the amplifier or antenna-feeder system, or an increase in the level of spurious emissions, the protection system will automatically turn off the amplifier and/or connect the transceiver directly to the antenna (“bypass” mode). To manually enable the bypass mode, simply turn off the power to the amplifier.

Input power 5 - 15 W.

Output power 300 W CW or 400 W PEP in SSB.

Supply voltage 13.8 V.

Maximum current consumption up to 45 A.

Dimensions 450x190x80 mm, weight 3 kg. Price (approximately in the Russian Federation) = $750

OM Power OM 1500

Linear power amplifier for operation on all amateur bands from 1.8 to 29 MHz (including WARC bands) + 50 MHz with all types of modulation. Equipped with a ceramic tetrode GS-23B.

Specifications:

Operating frequency range: amateur bands from 1.8 to 29.7 MHz, including WARC bands + 50 MHz.

Output Power: 1500+ Watts in SSB and CW modes on HF bands, 1000 Watts in SSB and CW modes on 50 MHz, 1000+ Watts in RTTY modes

Input Power: Typical 40 to 60 Watts for full power output.

Input Impedance: 50 ohms at SWR< 1.5: 1

Gain: 14 dB, Output Impedance: 50 Ohms, Maximum SWR: 2:1

SWR boost protection: automatic switch to STANDBY mode when reflected power exceeds 250 W

Intermodulation distortion: 32 dB of rated output power.

Harmonic Suppression:< -50 дБ относительно мощности несущей.

Lamp: GS-23B ceramic tetrode. Cooling: Centrifugal fan.

Power supply: 1 x 210, 220, 230 V - 50 Hz. Transformers: 1 toroidal transformer 2.3 KVA

Peculiarities:

Antenna switch for three antennas

Memory for errors and warnings - easy operation

Automatic anode current adjustment (BIAS) - no adjustment required after lamp replacement

Automatic adjustment of fan speed depending on temperature

Full QSK with silent relay

Smallest and lightest 1500W amplifier on the market

Dimensions (WxHxD): 390 x 195 x 370 mm, Weight: 22 kg

OM Power OM 2500 HF

The Russian-made GU84b tetrode is used to obtain an output power of up to 2700 Watts.

The amplifier uses a GU84B tetrode in a circuit with a grounded cathode (the input signal is fed to the control grid). The amplifier exhibits excellent linearity between the control grid bias voltage and the screen grid voltage. The input signal is fed to the control grid using a wideband transformer with an input impedance of 50 ohms. This input circuit provides an acceptable SWR value (less than 1.5:1) on all HF bands.

The output stage of the amplifier is a Pi-L circuit. The variable capacitor on ceramic insulators for circuit tuning and load matching is divided into two parts and designed specifically for this amplifier. This allows you to fine-tune the amplifier and easily return to previously tuned positions after changing the range.

The high anode voltage consists of 8 voltage sources of 300V/2A each. Each source has its own rectifier and filter. Safety resistors are used in the anode voltage circuit to protect the amplifier from overload. The grid voltage is stabilized by a circuit of IRF830 MOSFETs and is 360V/100mA. The control grid voltage -120V is stabilized by zener diodes.

Main technical characteristics of the power amplifier OM2500 HF

Output Power: 2500 Watts in CW and SSB modes, 2000 Watts in RTTY, AM and FM modes
< 2.0: 1 входное - 50 Ом при КСВ < 1,5:1
RF gain: no less than 16 dB
Protection units: when SWR, anode and grid currents increase, or when the amplifier is configured incorrectly, providing a soft start to protect fuses, blocking the switching on of dangerous voltages when the amplifier covers are removed
Dimensions and weight (in working condition): 485x200x455 mm, 38 kg

OM Power OM2000 HF

The power amplifier is designed to operate on all HF bands from 1.8 to 29 MHz (including WARC bands) in all operating modes.

High frequency block:

The amplifier uses a GU-77B tetrode according to a circuit with a grounded cathode with excitation supplied to the control grid. The amplifier has excellent linearity because the control grid bias and screen grid voltage are well stabilized. The input signal is fed to the control grid through a broadband matching device with an input impedance of 50 Ohms. This solution ensures matching of the amplifier input with an SWR of no worse than 1.5:1 on any HF band.

Power supply

Using a unit made of relays and powerful resistors, a powerful rectifier is soft-started. The high-voltage unit is composed of eight sections providing 350 volts at a current of 2 amperes, each of which has its own rectifier and filter. Safety resistors are installed in the anode voltage circuit to protect the amplifier from overload.

Amplifier protection

Main technical characteristics of the OM2000 HF power amplifier

Frequency range: all amateur radio bands from 1.8 to 29.7 MHz;
Output power, no less: 2000 W in CW and SSB modes, 1500 W in RTTY, AM and FM modes
Intermodulation distortion: no more than -32 dB from peak rated power.
Harmonic suppression: greater than 50 dB peak rated power.
Characteristic impedance: output - 50 Ohm, for asymmetric load, at SWR< 2.0: 1 входное - 50 Ом при КСВ < 1,5:1
RF gain: no less than 17 dB
Supply voltage: 230V – 50Hz, one or two phases
Transformers: 2 toroidal transformers, 2KVA each
Dimensions and weight (in working condition): 485x200x455 mm, 37 kg

OM Power OM2500 A

The power amplifier is designed to operate on all HF bands from 1.8 to 29 MHz (including WARC bands) in all operating modes. The OM2500 A automatically tunes to the transceiver frequency.

High frequency block

The amplifier uses a GU-84B tetrode according to a circuit with a grounded cathode with excitation supplied to the control grid. The amplifier has excellent linearity because the control grid bias and screen grid voltage are well stabilized. The input signal is fed to the control grid through a broadband matching device with an input impedance of 50 Ohms. This solution ensures matching of the amplifier input with an SWR of no worse than 1.5:1 on any HF band.

The amplifier output has a Pi-L circuit enabled. Each of the variable capacitors, designed to adjust the circuit and load, is made of ceramic insulators and is divided into two sections. This solution allows you to more accurately tune the amplifier and easily return to the previous settings after changing the range.

Power supply

The amplifier is powered by two two-kilowatt toroidal transformers.

Using a unit made of relays and powerful resistors, a powerful rectifier is soft-started. The high-voltage unit is composed of eight sections providing 420 volts at a current of 2 amperes, each of which has its own rectifier and filter. Safety resistors are installed in the anode voltage circuit to protect the amplifier from overload.

The voltage for the screen grid is provided by a parallel stabilizer assembled on high-voltage transistors of the BU508 type, which provides a voltage of 360 volts at a current of up to 100 mA. The bias for the control grid (-120 volts) is also stabilized.

Amplifier protection

The device provides continuous monitoring and protection of all circuits in case of disturbances in the operation of the amplifier. The protection unit is located on the control board installed in the subpanel.

Main technical characteristics of the power amplifier OM2500 A

Frequency range: all amateur radio bands from 1.8 to 29.7 MHz;
Output power, no less: 2500 W in CW and SSB modes, 2000 W in RTTY, AM and FM modes
Intermodulation distortion: no more than -32 dB from peak rated power.
Harmonic suppression: greater than 50 dB peak rated power.
Characteristic impedance: output - 50 Ohm, for asymmetric load, at SWR< 2.0: 1, входное - 50 Ом при КСВ < 1,5:1
RF gain: no less than 17 dB
Manual or automatic setting
Tuning speed on the same range:< 0.5 сек.
Tuning speed when tuning to another range:< 3 сек.
Supply voltage: 230V – 50Hz, one or two phases. Transformers: 2 toroidal transformers, 2KVA each
Protection units: if SWR, anode and grid currents increase, if the amplifier is configured incorrectly, providing a soft start to protect fuses, blocking the switching on of dangerous voltages when the amplifier covers are removed
Dimensions and weight (in working condition): 485x200x455 mm, 40 kg

OM Power OM3500 HF

The OM3500 HF power amplifier is designed to operate on all HF bands from 1.8 to 29 MHz (including WARC bands) in all operating modes. The amplifier has a GU78B ceramic tetrode.

The amplifier uses a GU78B tetrode in a circuit with a grounded cathode (the input signal is fed to the control grid). The amplifier exhibits excellent linearity between the control grid bias voltage and the screen grid voltage. The input signal is fed to the control grid using a wideband transformer with an input impedance of 50 ohms. This input circuit provides an acceptable SWR value (less than 1.5:1) on all HF bands. The output stage of the amplifier is a Pi-L circuit. The variable capacitor on ceramic insulators for circuit tuning and load matching is divided into two parts and designed specifically for this amplifier. This allows you to fine-tune the amplifier and easily return to previously tuned positions after changing the range.

The amplifier's power supply consists of two 2KVA toroidal transformers. The soft start mode occurs using relays and resistors.

Amplifier protection:

Constant monitoring and protection of anode and grid voltages and currents is carried out in case of incorrect amplifier settings, a soft start mode is implemented to protect fuses.

Technical characteristics of the power amplifier OM3500 HF:

Frequency range: all amateur radio bands from 1.8 to 29.7 MHz;
Output Power: 3500 Watts in CW and SSB modes, 3000 Watts in RTTY, AM and FM modes
Intermodulation distortion: better than 36 dB below peak rated power.
Harmonic Rejection: Better than 55 dB below peak rated power.
Characteristic impedance: output - 50 Ohms, for asymmetric load, input - 50 Ohms at SWR< 1,5:1
RF Gain: Typical 17 dB
Supply voltage: 2 x 230V – 50Hz, one or two phases
Transformers: 2 toroidal transformers, 2.5 KVA each
Dimensions and weight (in working condition): 485x200x455 mm, 43 kg

RM KL500

Amplifier RM KL500 HF range (3-30) MHz, input power 1-15 W, output 300 W with electronic switching technology and polarity reversal protection. It has six output power levels and a 26 dB antenna preamplifier.

Frequency: HF

Voltage: 12-14 Volts

Current consumption: 10-34 Amps

In. power: 1-15 W, SSB 2-30 W

Exit Power: 300W Max (FM) / 600W Max (SSB-CW)

Modulation: AM-FM-SSB-CW

Six power levels

Fuses: 3×12 A

Size: 170x295x62 mm

Weight: 1.6 kg Price (approximately in the Russian Federation) = $340

YAESU VL-2000

Great power combined with high reliability.

8 massive CMOS field-effect transistors of the VRF2933 type, connected in a push-pull circuit, provide the necessary output power in the range from 160 to 6 m. Two large fans with a continuous rotation speed control system effectively cool the PA and low-pass filter unit, providing years of reliable and silent operation .

Two large pointer instruments.

The left instrument shows the output power or SWR. Right – current consumption and supply voltage.

The monitoring system provides reliable and quick troubleshooting in the system.

In high-power devices, mains voltage fluctuations, temperature violations, high SWR levels, and exceeding the level of the RF drive signal at the input are monitored.

The built-in automatic high-speed antenna tuner matches your antenna to an SWR level of 1.5 or better in less than 3 seconds (according to the passport).

Two input and four output connectors allow integrated selection of the transmitter and the required antenna.

For example, two input connectors allow you to connect an HF transceiver to the first (INPUT 1), and a 6 m range transceiver to the second (INPUT 2). In this case, the output connectors can be connected to various antenna switching devices available at the station. Automatic selection of the required antenna can be performed for the transmitter connected to input 1 (INPUT 1), often eliminating the need for additional antenna switches. When the “DIRECT” toggle switch located on the rear panel is turned on, the amplified signal from input 2 (INPUT 2) is fed directly to the “ANT DIRECT” connector, bypassing the output switching system. In addition, the VL-2000 PA can be used in the SO2R system.

Automatic range switching for quick transitions.

Most modern Yaesu transceivers allow you to exchange data about the current range between the transceiver and the VL-2000 PA, which allows you to automatically change the range in the PA when you change the latter in the transceiver. To automatically change the range when using other types of transmitters, the VL-2000 PA has an automatic range detection function using a built-in frequency meter, which ensures an immediate change of range the first time an RF signal is applied to the PA input.

Specifications

Range: 1.8-30; 50-54 MHz
Antenna switch: ANT 1-ANT 4, ANT DIRECT
Power: (1.8-30 MHz) 1.5 KW, (50-54 MHz) 1.0 KW
Consumption: 63 A
Supply voltage 48 V
Types of work: SSB, CW, AM, FM, RTTY
Range switching: manual/automatic
Output transistor: VRF2933
Output stage operating mode: Class-AB, Push-pull, Power Combine
Spurious emissions: -60 dB
Input power: 100 to 200 W
Temperature: -10 +40 C
Dimensions 482x177x508 mm, Weight: 24.5 kg
Power supply: Output voltages: +48 V, +12 V, -12 V. Output current: +48 V 63 A, +12 V 5.5 A, -12 V 1A,
Dimensions: 482x177x508 mm. Weight: 19 kg

tagPlaceholder Tags:

(article updated on 02/07/2016)

UT5UUV Andrey Moshensky.

Amplifier "Gin"

Transistor power amplifier

with transformerless power supply

from the network 220 (230) V.

The idea of creating a powerful, lightweight and cheap high-power amplifier has been relevant since the birth of radio communications. Many excellent tube and transistor designs have been developed over the last century.

But there are still disputes over the superiority of solid-state or high-power electronic-vacuum amplifier technology...

In the era of switching power supplies, the issue of weight and size parameters of secondary power supplies is not so acute, but by actually eliminating it and using an industrial network voltage rectifier, you still get a gain.

The idea of using modern high-voltage switching transistors in a radio power amplifier, using hundreds of volts of DC for power, seems tempting.

We present to your attention the design of a power amplifier for the “lower” HF ranges with a power of at least 200 Watts with transformerless power supply, built according to a push-pull circuit using high-voltage field-effect transistors. The main advantage over analogues is weight and size indicators, low cost of components, and stability in operation.

The main idea is the use of active elements - transistors with a drain-source boundary voltage of 800V (600V) intended for operation in pulsed secondary power supplies. Field-effect transistors IRFPE30, IRFPE40, IRFPE50 produced by the International Rectifier company were chosen as amplifying elements. The price of the products is 2 (two) dollars. USA. They are slightly inferior in terms of cutoff frequency, providing operation only in the 160m range, 2SK1692 manufactured by Toshiba. Fans of amplifiers based on bipolar transistors can experiment with 600-800 volt BU2508, MJE13009 and others like that.

The method for calculating power amplifiers and SHPTL is given in the handbook of shortwave radio amateur S.G. Bunina L.P. Yaylenko. 1984

The winding data of the transformers is given below. The input SHPTL TR1 is made on a ring core K16-K20 made of M1000-2000NM(NN) ferrite. The number of turns is 5 turns in 3 wires. The output SHPTL TR2 is made on a ring core K32-K40 made of M1000-2000NM(NN) ferrite. The number of turns is 6 turns in 5 wires. The wire for winding is recommended MGTF-035.

It is possible to make an output SHTL in the form of binoculars, which will have a good effect on operation in the “upper” part of the HF range, although the transistors shown there do not function due to the rise and fall times of the current. Such a transformer can be made of 2 columns of 10 (!) K16 rings from material M1000-2000. All windings according to the diagram are one turn.

Measurement data for transformer parameters are given in the tables. The input SHTLs are loaded onto input resistors (the author has 5.6 Ohms instead of the calculated ones), connected in parallel with the gate-source capacitance, plus the capacitance due to the Miller effect. Transistors IRFPE50. The output SHPTLs were loaded from the drain side onto a non-inductive 820 Ohm resistor. Vector analyzer AA-200 manufactured by RigExpert. The overestimated SWR can be explained by the insufficiently dense laying of the transformer turns on the magnetic circuit, a noticeable discrepancy between the characteristic impedance of the MGTF-0.35 line required in each specific case. However, there are no problems on the 160, 80 and 40 meter bands.

Fig 1. Electrical circuit diagram of the amplifier.

Power source: bridge rectifier 1000V 6A, loaded on a capacitor 470.0 to 400V.

Do not forget about safety standards, the quality of radiators and mica gaskets.

Fig 2. Electrical circuit diagram of a direct current source.

Fig 3. Photo of the amplifier with the cover removed.

Table 1. Parameters of TR1 SHTL, made on the K16 ring.

Frequency kHz	R	jX	SWR
1850	45,5	+4,2	1,15
3750	40,5	+7,2	1,3
7150	40,2	+31,8	2,1

Table 2. Parameters of TR2 SPTL, made on the K40 ring.

Frequency kHz	R	jX	SWR
1800	48	-0,5	1,04
3750	44	-4,5	1,18
7150	40,3	-5,6	1,28
14150	31,1	4,0	1,5
21200	X	X	1,8
28300	X	X	2,2

Fig 4. Output SHTL on ring K40.

Table 3. Parameters of TR2 SPTL, “binoculars” design.

Frequency kHz	R	jX	SWR
1850	27,3	+26	2,5
3750	46	+17	1,47
7150	49	-4,4	1,10
14150	43	-0,9	1,21
21200	X	X	1,41
28300	X	X	1,7

Fig 5. Output SHPTL of “binoculars” design.

By connecting transistors in parallel and recalculating the SPTL, the power can be significantly increased. For example, for 4 pcs. IRFPE50 (2 in arm), output SHTL 1:1:1 and power supply 310V at the drains, an output power of 1kW is easily obtained. With this configuration, the efficiency of SHPTL is especially high; the method of performing SHPTL has been described repeatedly.

The author's version of the amplifier with two IRFPE50, shown in the photographs above in the text, works great on the 160 and 80 m ranges. Power is 200 Watts at a load of 50 Ohms with an input power of about 1 Watt. The switching and bypass circuits are not shown and depend on your wishes. Please pay attention to the absence of output filters in the description, operation of the amplifier without which is unacceptable.

Andrey Moshensky

Addition (02/07/2016):
Dear readers! Due to numerous requests, with the permission of the Author and the editors, I am also posting a photo of the new design of the “Gin” amplifier.

In the actual design of the transceiver, a fairly powerful amplifier is used, the peak power reaches 100W. Today, due to the current prices for high-power RF transistors, this is a rather expensive unit. The pre-final and final stages use domestic transistors, specially designed for linear amplification of the 1.5-30 MHz range at a supply voltage of 13.8 V.

For now, I’ll give you a stripped-down version of the silo with an output power of up to 5W. Its cost is not high, so it will be available to most radio amateurs. The output power is almost the same on all bands. If desired, you can make the output power in high-frequency sections greater than in the low-frequency sections. This is sometimes required when using an external PA with a blockage on the HF Bands. The first stage is made using a KT610 transistor. The best replacement for it is the KT939A, such a transistor is specially designed for linear amplification in class A. There are more modern transistors with even better characteristics, but they are very difficult to find. For example, 2T996B, which has a coefficient of combination components at a frequency of 60 MHz for the second harmonic (M2) no more than 65 dB, and for the third harmonic (M3) no more than 95 dB, not every lamp can provide such parameters. Transistor VT1 is used in class A with a quiescent current of 120-150mA. Transformer T1 is made on a ferrite ring with a diameter of 10 mm, permeability 1000. Winding in two wires without twisting, a wire with a diameter of 0.24-0.30 mm, eight turns, connecting the beginning of one winding to the end of the other forms the middle terminal. The increase in HF gain is provided by negative feedback in the emitter circuit, selected using C1. The overall gain and slope of the frequency response can be selected by changing the ratings of R5, C2. The amplified signal through the isolation capacitor C6 is supplied to the final stage VT2. It was not possible to find a replacement for this transistor without deteriorating performance. More or less, KT920B,V are still working here; KT925B,V. You can use KT921A, KT922B, KT934B, G, but these are transistors intended for use with a supply voltage of 24V. Therefore, we can assume a decrease in the gain and frequency properties with a 13.8V supply. It’s also difficult to say anything about linearity, because... Of all those listed, only KT921A is intended for these purposes, the rest are designed to amplify the FM signal at frequencies above 50 MHz in class C. Such transistors can be used in the HF range with acceptable linearity only at reduced power (no more than 40%). If the reader would like to get acquainted in more detail with the author’s opinion regarding the construction of transistor silos with a 24V power supply on a domestic element base, he can order a book describing a network transceiver with a frequency synthesizer on the Z80 and such a power amplifier. When using KT965A in this stage and a 13.8-14V power supply, you can get at least five linear watts of power. When comparing the SK4-59 5W spectrum analyzer obtained in the TRX RA3AO and the same power using the KT965A, I immediately felt the desire to throw out the A21 node in the “drozdiver”. The push-pull amplifier on the KT913 (A21) ensures the presence of “sticks” on the analyzer screen up to the maximum frequency of the device (110 MHz), and maybe higher, because The resolving frequency properties of the SK4-59 simply do not allow it. The KT965 transistor is not designed to operate above 30 MHz, so it simply does not “pull” at such frequencies and traces of “sticks” can only be seen at frequencies up to 50 MHz, harmonics are suppressed in the worst case by at least 25 dB. This signal can be used on the air and excite any power amplifier without any filters. Figure 6 shows a two-stage low-frequency filter installed at the output of the amplifier, which cuts off those remnants of “sticks” that can still be seen on the analyzer screen above 32 MHz (L6, L7, C20, C21, C22). In the case of a “trimmed” silo, this low-pass filter does not need to be installed. The base current VT2 is stabilized by the chain VD1, VD2, VT3. Elements C4, R8 determine the amplitude-frequency response of the cascade. Negative feedback resistors R10,R11 improve linearity. Resistor R7 serves to prevent breakdown of the emitter junction during the reverse half-wave of the control voltage and is calculated by the formula R=S/2pFgr.Se. The quiescent current is in the range of 300-350mA, set by resistor R9. The T2 transformer can be made on a ferrite ring with a diameter of 16-20 mm with a permeability of 300-600, or you can use “binoculars” from K10 rings with a permeability of 600-1000, 4 rings in a column are enough. If the expected load is 50-75 Ohm, you need to transform the resistance 1:4; for these purposes, a transformer on a ring wound bifilarly with 0.6-0.8 mm wire is suitable, 7-9 turns are enough. The middle terminal, formed by connecting the beginning of one winding to the end of another, is connected to the collector VT2. From one free output, through a separating capacitor with a capacity of 47-68N, a reactive power of at least 10 W, we remove the useful signal, and the supply voltage is supplied to the other end of the winding. If the load resistance may be more than 100 Ohms or it is unknown, it is better to use a “binoculars” type transformer, because With such a transformer it is easier to change the ratio of transformed resistances. It is done this way - you need to glue two columns from the rings, then glue the columns together like “binoculars”. Winding I can be 1-2 turns of wire with a cross-section of at least 0.6 mm. If the load resistance is unknown, winding II is first wound with a obviously large number of turns, for example 5; a stranded mounting wire can be used. Then, guided by the readings of the current consumed by the cascade on VT2, and the readings of a lamp voltmeter connected in parallel with the load, we find the optimal ratio of transformer turns. It is necessary to check the output power value at the highest frequency - 29 MHz, in the middle of the ranges - 14 MHz and at 1.8 MHz. The chain of resistors R12, R13 in the powerful version of the silo is called “fool protection”. Here it serves as a divider when measuring output power. Elements R14,C15 compensate for the unevenness of the power meter over the entire frequency range from 1.5 to 30 MHz. Resistor R15 is used to calibrate the milliammeter readings. To ensure that the divider does not take away part of the useful power, you can proportionally increase the resistance R12, R13, but then the “protection” functions will not be performed. Relay P1 type RES10 or its sealed analogue - RES34, passport 0301, winding resistance about 600 Ohm, first check for reliability of operation from 11-12V. You can use 12-volt passports with a winding resistance of 100-120 Ohms, but then VT4 needs to be replaced with a more powerful transistor (KT815). Chokes Dr1 and Dr3 must withstand operating current - Dr1 up to 150mA, Dr3 up to 1A.

Power amplifier 50-100W.

The circuitry of transistor broadband power amplifiers has been worked out and if you look at the circuits of imported transceivers, both the cheapest and the most expensive models, the differences in the construction of these units are minimal, the differences are only in the names of the transistors, the ratings of the parts and insignificantly in the circuit. If the reader is familiar with the previous book - a description of the network TRX, in which the KT956A silo is used, then he can note the minimal difference in the construction of such cascades. Since the transceiver is designed to operate from a 13.8V power supply, the search was aimed at providing the required power with a minimum drop in the amplitude-frequency response in the high-frequency region and maintaining linearity when the supply voltage drops to 11V. The choice of domestically produced transistors for solving this problem is very small. If we also take into account that their cost is usually higher than transistors designed to operate from 24-28V and they are quite rare on radio markets, then before you start making such an amplifier you should think about whether you need to make heroic efforts to focus on these the notorious, accepted all over the world 13.8V? Can he make a silo from the “radio junk” that is available? There are KT960, KT958, KT920, KT925, which are quite often used by radio amateurs.

Low frequency (cutoff frequency up to 3 MHz)
High frequency (cutoff frequency up to 300 MHz)
Ultra-high frequency (cutoff frequency above 300 MHz).

We are interested in the second group, within it the transistors are divided into:

A) designed for linear amplification of the RF signal
B) for broadband signal amplification in class C at frequencies of 50-400 MHz.

It is better to read in more detail about how certain transistors are designed and manufactured in professional literature. Here we note only the main differences between subgroups “A” and “B”. Group A, transistors intended for communication equipment are mainly linear broadband amplifiers operating in single sideband mode; additional requirements are imposed on transistors both in terms of design (reducing the collector capacitance and inductance of the emitter terminal) and linearity. In high-power RF transistors for communication equipment, the amplitude of the combinational components of the third and fifth orders is 25-30 times less than the amplitude of the main signals (attenuation of at least 27-33 dB). When manufacturing transistors of this group, manufacturers focus on linearity parameters and safety margins in extreme operating conditions. In subgroup B, more attention is paid to frequency properties and increasing the power gain. For example, two transistors designed to produce the same power of 20W - KT965A (subgroup A) and KT920V (subgroup B) differ in their maximum operating parameters. KT965A - collector current 4A, power dissipation 32W with a power supply of 13V; KT920V - respectively 3A, 25W at 12.6V. Since the cutoff frequency of transistors designed to operate below 30 MHz is quite low (up to 100 MHz), it is easier for the manufacturer to produce a device with a higher overload capacity. For example, the minimum dimensions of transistor elements at frequencies of 200-500 MHz are 1 µm or less, while for frequencies of 50-100 MHz they can be 3-4 µm in size. It was necessary to verify in practice that the overload capacity of transistors designed for linear amplification of the HF range is higher than that of devices with higher frequencies, but used by radio amateurs at frequencies up to 30 MHz. For example, a silo with an output power of 70W on the KT956A can withstand an SWR of up to 10 in long-term mode and has fairly good linearity, which cannot be said about exactly the same amplifier on the KT930B. RU6MS has been using a KT956A silo with an output power of 100-130W as an attachment to the Katran for several years now, loading the amplifier directly onto the antenna without any coordination. There is no interference with television, even when using “Polish” active antennas. Before this, he tried to operate an amplifier published by Skrypnik in the magazine "Radio" and, apart from the nervous stress after the next replacement of the KT930B, the inability to work on the air when his beloved wife was watching the next series on TV, as far as I know, no other experience was gained. RK6LB uses an industrial unit with twelve KT956A (power up to 500W) and operates quietly on the air at a distance of 4 meters between the amplifier and the head cable television station, which generates signals for six television channels. Similar linearity and reliability parameters can be obtained by using transistors designed for a 13.8V power supply. Unfortunately, the list of such products produced by the domestic industry is very small - these are KT965A, KT966A, KT967A. More modern types of transistors are very rarely found on radio markets. Maximum output power values can be obtained by using KT966A and KT967A, but we will not consider these versions of silos here due to the scarcity of transistors. Enough linear 50-60W output power can be obtained with the more affordable KT965A. If you plan to use the battery frequently, then you can stop there.

It should be taken into account that the majority of radio amateurs still use a GU19 output stage in their transceiver with the same energy parameters and they cannot appreciate the excellent purity of the air during power outages. And if there are still daily “scheduled” shutdowns, then users of lamp technology can only sympathize. They lose not only time, but also the enormous pleasure of listening to bands when there is no interference, when the power goes out in a fairly large area. In the case when you need a power of at least 100 W with a 12V battery, you will need KT966,967 or imported analogues of such transistors, but then the cost of the transceiver increases sharply and it is more logical to purchase something ready-made branded rather than “reinvent the wheel”. You can try to use transistors designed for 27V for a low-voltage supply - these are KT956A, KT957A, KT944A, KT955A, KT951B, KT950B, but, as experience has shown, you will have to come to terms with the deterioration of energy characteristics and linearity. One of the versions of the transceiver used by UA3RQ was as follows - KT956A is used with a supply voltage of about 20V, and when the network is turned off, three series-connected alkaline batteries with a voltage of 19V are connected. Two types of available high-power RF transistors - KT958A and KT960A suggest their use in such a transceiver, because They are designed for a supply voltage of 12.6 V but for class C. According to the technical conditions, if these devices are used in modes of classes A, AB, B, the operating point should be in the area of maximum modes, i.e. It is more preferable to work with CW and limited SSB signal. To ensure sufficient reliability, output power is no more than 40W. It is desirable to work with a matched antenna load, otherwise the line of silos based on such transistors is prone to overexcitation.

The amplifier is made on a printed circuit board screwed to the rear wall-radiator of the case. Soldering parts on one side of the board on etched pads. This installation method allows you to easily attach the board to the radiator and provides access to replacing elements without turning the board over, thereby simplifying the process of setting up the silo. The board supply voltage is 13.8V; if a separate stabilized powerful power supply for the transceiver is used, then the voltage for this unit can be raised to 14.5V, and for the remaining TRX stages an additional stabilizer of 12-13V can be introduced. This measure allows you to increase the overall gain and, accordingly, will facilitate the task of obtaining a uniform frequency response. The same power at an increased voltage can be obtained at a lower current and thereby reduce the drawdown of the supply voltage on the supply wires. We must not forget that with a low-voltage transceiver power supply and a fairly high output power, the current consumption can reach significant values. With an output power of 50-60W, the current consumption exceeds 7A. Long supply wires between the power supply and the transceiver have a negative impact on the stability of the supply voltage. For example, on a 1m-long network “cord” from a burnt-out 100W soldering iron, used to supply supply voltage from the power supply to the transceiver, the voltage drop at a current of up to 10A can reach 0.3-0.5V, add here the drawdown on the wires inside the transceiver from the connector to switch and back to the silo board, as a result, at the collectors of the output transistors at maximum power, instead of 13.8V, which the power supply is configured for, we have 13-13.3V. This does not improve the amplifier's linearity or power performance.

The silo is three-stage, the first stage operates in class A mode, the second - class AB and the final stage in class B. The circuitry is similar to that used in imported transceivers and domestic communication equipment, because Such units are well developed and there is no point in “surprising the world” with amateur radio designs. The main tasks when constructing transistor silos are to ensure the most linear frequency response, reliability and stable operation at a load different from the nominal one. Uniform power delivery over the entire operating frequency range is solved by selecting the types of transistors, additional frequency-dependent negative feedback circuits, selecting appropriate broadband transformers and design. Reliable and stable operation is ensured by all kinds of overload protection, choice of types of radio elements and design.

The first stage of the amplifier is made on transistor VT1, which can be used as KT610, KT939 or the more modern 2T996B. Of the available transistors, the best is KT939A, because it is specifically designed for Class A amplifier operation with increased linearity requirements. According to the manufacturer's data, the 2T996B transistor provides linearity figures that are hard to believe - the coefficient of combination components at a frequency of 60 MHz for the second harmonic (M2) is no more than 65 dB, and for the third harmonic (M3) no more than 95 dB, not every lamp can provide such parameters. The quiescent current depends on the type of transistor used and is at least 100-160mA. The first stage must operate in a hard class A mode with a minimum of “garbage” in the output signal, because This will determine not only what we get at the output of the silo line, but also the overall gain of the useful signal. Subsequent stages are also broadband and they will equally amplify all signals arriving at their input. If there are a large number of harmonics in the input signal, part of the power will be wasted on amplifying them; due to the combinational interactions between them, this will further worsen the overall linearity. If we look at this situation with a spectrum analyzer, we will find at the output of the cascade an even larger palisade of “sticks” of harmonics than is visible in the input signal. The quiescent current of the first stage is regulated by resistor R2. The maximum output at a frequency of 29 MHz is controlled by capacitor C1. Chain R5,C1 determines both the overall gain and the slope of the frequency response. The T1 transformer is made on a ferrite ring K7-10 with a permeability of 1000, bifilar winding without twisting with two wires with a diameter of 0.15-0.18 mm evenly throughout the entire ring, 7-9 turns are enough. The beginning of one winding is connected to the end of the second and forms the middle terminal. Choke Dr1 must withstand the current consumed by the transistor. When setting up the first stage, the main attention should be paid to the linearity of the stage and maximum output at 29 MHz. You should not get carried away with increasing the cascade gain by decreasing R3, R4 and increasing R5 - this will lead to a deterioration in the linearity and stability of the entire silo. Depending on how much power we want to receive, the RF voltage on the collector VT1 loaded on VT2 is 2-4V. Next, the amplified signal through C6 goes to the second stage, which operates with a quiescent current of up to 350-400 mA. Capacitor C6 determines the frequency response and in the case of a blockage of 160 m, its rating can be increased to 22-33N. The KT965A transistor is used here. At first glance, this is not a completely logical solution, because... the transistor is “very powerful” for such a cascade and is used here at 15-20% of what is “inherent” in it. Attempts to use a “weaker” transistor in this stage did not give the desired results. High-frequency 12V transistors of the series available - KT920, KT925 with different letters, even if they provided energy parameters, did not give a small number of “sticks” in the output signal on the screen of the spectrum analyzer. The KT921A transistor, with good linearity, does not provide the required frequency response when supplied with a voltage of 13.8 V and does not drive the output stage to the required power in the HF ranges. Only when using the KT965A was it possible to obtain up to 5W of a linear signal from this stage. By the way, if there is no requirement to obtain high power from such a transceiver, then the construction of a silo can be completed on this stage. Transformer T2 should be turned on in reverse, i.e. winding II into the collector circuit, and winding I into the load. It will be necessary to select the ratio of winding turns for optimal matching with the load. But even with T2 switched without selecting the ratio of turns in the windings, at a load of 50 Ohms, the line of transistors 2T355A (DFT board), 2T939A and 2T965A provides 13-16V effective voltage. The current consumption reaches 1.3-1.5A, the efficiency is low, but this is the price for high signal linearity. If you cannot find KT965A, then it is advisable to make this cascade push-pull using KT921A transistors, Fig. 8. You will have to put up with some rollover at frequencies above 21 MHz; the output power with such a stage reaches 10W. It is possible to obtain a spectrally very pure signal with a linear frequency response of up to 5W by increasing the negative feedback with elements R5-R8,R10,C9,R11,C10. The diagram shows separate bias circuits separately for each transistor - this is a version for the “poorest radio amateur” who does not have the opportunity to select a pair of VT2, VT3 with identical characteristics.

If the selection of transistors is expected, then the power supply circuits of the bases can be combined. First, using resistors R14, R15 in the base current stabilizer chains, you need to set the quiescent current within 150-200 mA for each transistor, and then more accurately adjust it to suppress the nearest even harmonic, which can be heard on an additional receiver. The limits for adjusting the quiescent current depend on the slope of the transistors used and the number of diodes VD1, VD2 and VD3, VD4 connected in series. There are transistors in which, to obtain a quiescent current of up to 200 mA, one switched on diode is enough. Chains C7, R1 and C8, R2 provide an increase in the amplitude-frequency response in high-frequency ranges. Choke Dr3 must provide the current required by the cascade (up to 2A) without a voltage drop across it. It can be wound on a small ferrite ring with a permeability of 600 or more, with a wire with a diameter of at least 0.6-0.7 mm, 10-20 turns are enough.

Transformer T1 is made in the form of “binoculars” made of ferrite rings with a diameter of 7 mm, permeability 1000-2000. The “binoculars” columns are glued together from 3-4 rings depending on their thickness, the height of the column is 9-11 mm. The primary winding is 2-3 turns of mounting wire in fluoroplastic insulation, the secondary winding is 1 turn of PEL wire 0.7-0.8 mm.

Transformer T2 is also made in the form of “binoculars”. Two columns are glued together from ferrite rings with a permeability of 1000, a diameter of 10 mm, and a column height of 13-16 mm. You can also use rings with a permeability of 1000-2000 with a diameter of 7 mm, the height of the columns is 10-11 mm. The primary winding is 1 turn of braid from a thin coaxial cable with a tap from the middle or one turn of folded two mounting wires in fluoroplastic insulation, the beginning of one is connected to the end of the second and forms the middle terminal. A turn is counted when the wire enters one “binocular eye” and returns from the second. The secondary winding, in the case of using a braid from a coaxial cable for winding I, passes inside this braid, but if a mounting wire is used for the “primary”, then winding II is passed through the holes of the posts in the same way as winding I, only with the leads in the opposite direction. The number of turns of winding II can vary from 2 to 5, depending on the design of winding I, and they will have to be selected experimentally based on the best efficiency and optimal frequency response of the output stage at the required load resistance.

“Binoculars” cannot be glued to a printed circuit board without insulation, because Some brands of ferrites pass direct current. It should be noted that the low-pass filter on elements C34, L1, C35, L2, C36 is designed for a resistance of 50 Ohms. If the load differs significantly from this value, the filter must be recalculated or eliminated, because In this case, it will introduce unevenness into the frequency response of the amplifier. Let's return to the diagram in Fig. 9. Resistor R7 serves to prevent breakdown of the emitter junction during the reverse half-wave of the control voltage and is calculated by the formula R=S/2pFgrSe. The base current VT2 is stabilized by the chain VD1, VD2, VT3, R9, C9. Resistor R9 sets the quiescent current. Using negative feedback elements R8, C4, R10, R11, you can set the required frequency response and cascade gain. There is no need to install VT3 on the heatsink. Choke Dr3 must withstand current up to 1.5A.

Setting up the cascade consists of selecting the quiescent current with resistor R9, correcting the amplitude-frequency response and gain with resistor R8 and, to a lesser extent, capacitor C4. Pre-winding I of transformer T2 should be wound with 3 turns. The final selection will be made when setting up the entire silo.

Antiphase signals from transformer T2 through chains C16, R15, C17, R16 forming the required frequency response are supplied to output transistors VT6, VT5. Resistors R8, R17 serve the same purpose as R7. Using C15, winding 2 of transformer T2 is tuned to resonance at the highest operating frequency (29.7 MHz).

The information on output transistors VT6,VT5 is as follows. The type of transistors used depends on the expected output power. The most powerful and, accordingly, expensive are the KT967A. They can produce output power of more than 100W with very high reliability. It is possible to use KT956A, but with a supply voltage of 13.8V, these transistors have a sharp drop in gain in high-frequency ranges and linearity. There is only one way out - to increase the supply voltage to at least 18-20V. With KT965A transistors in the output stage it is possible to obtain 50-60W with acceptable reliability. Although the reference books indicate an output power of 20 W per transistor, this is precisely the rare case when the “standard” power is indicated when used in industrial and military equipment with a large margin of reliability. As an experiment, with a pair of 2T965A at 50 Ohm equivalent it was possible to obtain 90 W in the low frequency ranges. With an output power of 40-45W, the amplifier can withstand almost any SWR in long-term mode; such operation, of course, cannot be called optimal. Because when working for a long time with high SWR values, for example, several users of this technique stubbornly use one “wire” for all ranges (calling it an antenna), usually once or twice a year they change the first transistor of the ShPU line - KT355A. The “reflection” wanders around the transceiver and the weakest point turned out to be in the first stage. With KT966A transistors you can get at least 80W of output power, but they have more of a rollover in the HF ranges. As the experience of long-term use of these transistors with an SWR of up to 1.5-2 has shown, they can withstand a double power overload. More common and cheaper transistors, unfortunately, do not provide such parameters. For example, when using KT920V, 925V it is possible to achieve a linear 40W with a stretch; if this figure is exceeded, the reliability drops sharply and the level of out-of-band emissions increases.

Additionally, the gain and frequency response can be adjusted using chains R19, C30 and R20, C27. The base displacement stabilizer is made on elements VD4, VD5, VT4. Transistor VT4 is screwed to the radiator through a mica gasket. The Dr4 choke is wound on a ferrite rod from the largest and longest chokes (DM3) or on a ferrite ring with a permeability of 600-1000, with a diameter of 14-16 mm for ease of winding, a wire with a diameter of at least 0.8 mm on the rod before filling, 7-10 on the ring is enough turns. Chokes Dr5, Dr6 can be used types DPM-0.6 or wound on ferrite rings with a diameter of 7 mm, permeability 600-1000, 5 turns of PEL wire 0.35-0.47 mm are enough.

Transformer T3 is a “binoculars” made of rings with a diameter of 10-12mm, permeability 600-1000, column length 28-24mm. Winding 1 - one turn of braid from a coaxial cable, winding 2 - two or three turns of mounting wire in fluoroplastic insulation, laid inside the primary winding. The exact number of turns of the secondary winding is selected when tuning to the required load resistance and rated output power for a uniform frequency response and the best cascade efficiency.

The quiescent current is 200-250mA per transistor, selected by resistor R24. More accurately, the quiescent current can be set based on the greatest suppression of even harmonics, which can be monitored with a spectrum analyzer or an additional receiver. Output transistors require mandatory pair selection. Selection at low current is not optimal - you need to check the characteristics at collector currents of 50mA, 300mA, 1A. Moreover, transistors with similar characteristics at direct current should also be paired at HF for the same output power. Because for example, the “coolest” DC transistors are very often inferior in RF output to transistors with “below average” parameters. The task of successfully selecting a pair of output transistors is quite simple to solve - if there are at least a dozen transistors available. The hope that separate power supply to the bases can compensate for the spread - alas - “takes place” only with a small spread. Our industry has produced these products so disgracefully that the variations are as follows: at direct current with the same base bias, the collector current can fluctuate from 20 to 300 mA, and the amplitude of the RF voltage at the load with the same “swing” can be 20 , and 30V. It is difficult to imagine what the silo will produce if two transistors with extreme dispersion values are used in the output stage. It is clear that neither the user nor the listeners will receive satisfaction from the work of such a “miracle”.

In a real silo design, differences in the parameters of output transistors are reflected by a decrease in output power, uneven heating of transistors (the “cooler” one heats up more), due to the skew of the arms, an increased content of harmonics in the output signal (up to the appearance of TVI), low efficiency. Unfortunately, it is not possible to select a high-quality pair of transistors for the output stage with just one tester, so if you have a very strong desire to make such an amplifier, but cannot purchase enough to select a pair, as a last resort, you can contact the author of these lines for help, no Just remember that my possibilities are not limitless.

A “foolproof protection” is soldered to the output winding of transformer T3, consisting of resistors R21, R22. If the load on the silo line disappears or an unknown structure is connected instead of the antenna, then all the power will be dissipated on these resistors. Sooner or later, these resistors will give off the smell of burnt paint - a signal to the careless “exploiter” - look, “something is wrong, we’re burning.” This simple but effective protection allows, if necessary, to switch on the transceiver to transmit to an unknown load without much fear. The higher the load resistance is 50 ohms, the more power is dissipated on these resistors. Situations when load resistance lower than 50 Ohms occur much less frequently, and experience shows that the amplifier can more easily withstand a short-circuit load than its absence. No matter how low-impedance the load is, there is always the reactance of the coaxial cable with which it is connected and the reactance of the low-pass filter, so it is quite difficult to obtain an absolute short circuit at the PA output, of course, unless you specifically simulate such a situation. As one of Murphy's laws says: "Fool-proofing works until an inventive fool appears."

Chain R24,C37,VD6,C38,R23 is used to measure output power. Elements R24,C37 are selected in such a way as to compensate for the unevenness of power measurement from frequency. Resistor R23 regulates the sensitivity of the meter.

The low pass filter with a cutoff frequency of 32 MHz consists of C34, L1, C35, L2, C36. It is designed for a 50 Ohm load. The low-pass filter should be additionally adjusted to the highest output at 28 MHz, shifting and moving apart the turns of the coils L1, L2. If an additional matching device is used between the transceiver and the antenna or when working with an external power amplifier, it is sufficient to suppress out-of-band emissions. In a properly manufactured and tuned amplifier, the level of the second harmonic is no more than -30 dB, the third harmonic is no more than -18 dB, and third-order Raman oscillations at the peak of the envelope of a two-tone signal are no more than -32 dB.

Contacts K1 of relay P1 connect the antenna socket to the silo in transmit mode. Relay P1 is controlled via transistor switch VT4 by voltage TX. Diode VD3 serves to protect transistor VT4 from reverse current surges when switching the relay. P1 types RES10, RES34 with a winding resistance of up to 400 Ohm, it must first be checked for reliability of operation from 12-13V. Some relays, for example RES10 passports 031-03 02, 031-03 01, with a supply voltage of 13.8 V, work reliably during the first two to three weeks, and then when the PA compartment, where these relays are located, heats up, they begin to fail - the contacts do not reach enough and do not connect the silo output to the antenna. Perhaps this was due to the low quality of the relay, although a dozen relays from the same box have been working flawlessly for several years. You can also use RES10 with a winding resistance of 120 Ohm, passport 031-04 01, but you need to take into account that it consumes about 110 mA, with a 13.8 V power supply the TRX heats up, which does not improve the overall temperature regime of the silo compartment, accordingly the maximum collector current of transistor VT4 should be no less than this value. When using RES10 as described above, KT315 can be used as VT4.

An interesting feature of the domestic element base has been noticed - it requires a preliminary “test”, a run for at least one to two weeks and preferably in different temperature conditions, i.e. The transceiver should be turned on and off so that it heats up during operation and cools down when turned off. Then those parts that “should fly out” due to their low quality will “fly away” faster and will not lead to “nervous stress” at the most inopportune moment, as most often happens. After such testing, the transceiver, with proper and careful operation, as a rule, works flawlessly for years.

RF Power Amplifiers

HF LINEAR TUBE POWER AMPLIFIER TODAY

Part one

Many shortwave operators are convinced that everything is known about tube amplifiers. And even more... Maybe. But the number of low-quality signals on the air is not decreasing. Quite the contrary. And the saddest thing is that all this is happening against the backdrop of an increase in the number of industrial imported transceivers in use, the transmitter parameters of which are quite high and meet the requirements of the FCC (American Federal Communications Commission). However, some of my colleagues on the air, who have come to terms with the fact that you can’t make the FT 1000 “on the knee” and use RAs designed according to the canons of thirty years ago (GU29 + three GU50s), etc., are still confident that according to RA “we ahead of the rest." Let me note that “they are there, abroad,” not only buying, but also constructing RAs that are worthy of attention and repetition.

As you know, KB power amplifiers use circuits with a common grid (OC) and a common cathode (CC). The output stage with OS is almost a standard for radio amateurs in the CIS. Any lamps are used here - both those specially designed to work in a circuit with OS, and lamps for linear amplification in circuits with OK. Apparently, this can be explained by the following reasons:
- the circuit with OS is theoretically not prone to self-excitation, because the grid is grounded either by HF or galvanically;
- in the circuit with feedback, linearity is 6 dB higher due to negative current feedback;
- RA with OS provide higher energy levels than RA with OK.

Unfortunately, what is good in theory is not always good in practice. When using tetrodes and pentodes with a high slope of the current-voltage characteristic, the third grid or beam-forming plates of which are not connected to the cathode, the RA with OS can self-excite. If installation is unsuccessful, low-quality components (especially capacitors) and poor matching with the transceiver, conditions for phase and amplitude balance are easily created to obtain a classic self-oscillator on HF or VHF using a circuit with OS. In general, matching a transceiver with an RA according to the OS scheme is not as simple as it is sometimes written. Often cited figures, such as 75 ohms for four G811s, are only theoretically correct. The input impedance of the PA with feedback depends on the excitation power, anode current, P-circuit settings, etc. Changing any of these parameters, for example increasing the SWR of the antenna at the edge of the range, causes mismatch at the input of the stage. But that's not all. If a tuned circuit is not used at the input of the PA with OS (and this is a common occurrence in homemade amplifiers), then the excitation voltage becomes asymmetrical, because The current from the exciter flows only during the negative half-cycles of the input voltage, and this increases the level of distortion. Thus, it is possible that the above factors will negate the advantages of the OS scheme. But, nevertheless, RA with OS are popular. Why?

In my opinion, due to excellent energy performance: when it is necessary to “pump up power”, there is no price for a circuit with OS. In this case, the linearity of the amplifier is the last thing people think about, referring to what is firmly understood - “the distortions introduced by the cascade depend little on the choice of the operating point on the characteristic.” For example, a GU74B lamp designed for linear amplification of single-sideband signals in a typical connection in a circuit with OK should have a quiescent current of about 200 mA, and it is unlikely that it will be possible to obtain an output power of more than 750 W (at Ua = 2500 V) without risking the longevity of the lamp, t .To. the power dissipation at the anode will be limiting. It’s another matter if the GU74B is turned on with the OS - the quiescent current can be set to less than 50 mA, and an output power of 1 kW can be obtained. It was not possible to find information about measuring the linearity of such RAs, and arguments like “many QSOs were conducted on this amplifier, and correspondents invariably noted the high quality of the signal” are subjective and therefore unconvincing. Power of more than 1 kW in the above example is provided by the popular industrial ALPHA/POWER ETO 91B, using a pair of GU74B lamps with OK in the operating mode recommended by the manufacturer with known intermodulation characteristics. Apparently, the developers of this amplifier were concerned not only with economic considerations (another lamp increases the cost and complexity of the design), but also with the compliance of the PA parameters with the standards and requirements of the FCC.

The advantage of RA with OS is the absence of the need to stabilize the voltages of the screen and control grids. This is true only for a circuit in which the specified grids are directly connected to a common wire. Such inclusion of modern tetrodes can hardly be considered correct - not only is there no data on the linearity of the cascade in this mode, but also the power dissipation on the grids, as a rule, exceeds the permissible limit. The excitation power for such a circuit is about 100 W, and this causes increased heating of the transceiver, for example, during intensive work on a general call. In addition, with a long connecting cable, it is necessary to use a switched P-circuit at the amplifier input in order to avoid high SWR values and related problems.

The disadvantages of circuits with OK include the need to stabilize the voltages of the screen and control grids; however, in modern tetrodes in AB1 mode, the power consumed by these circuits is small (20...40 W), and the voltage stabilizers on currently available high-voltage transistors are quite simple. If the power transformer does not have the necessary voltages, you can use suitable low-power transformers by connecting them the other way around - with the secondary winding to a filament voltage of 6.3 or 12.6 V. Another disadvantage of the OK circuit is the high power dissipation at the anode during transmission pauses. One of the possible ways to reduce it is shown in Fig. 1 (simplified diagram from).

The excitation voltage is supplied through a capacitive divider to the full-wave rectifier VD1, VD2 and then to the comparator DA1. Triggering of the comparator transfers the lamp from the closed state to the operating mode. During transmission pauses, there is no excitation voltage, the lamp is locked, and the power dissipated at the anode is negligible.

In my opinion, RA with OS can be used on KB with outdated lamps - to reduce the cost of the design, or with lamps specially designed to work in such a connection. The use of a tuned LC circuit of low quality factor or a P-circuit at the input is mandatory. This is especially true for transceivers with wideband transistor output stages, the normal operation of which is possible only with a matched load. Of course, if the output stage of the transceiver has a customizable P-circuit or antenna tuner, and the length of the connecting cable does not exceed 1.5 m (i.e., it represents a capacitance for the frequency range used), such a circuit can be considered as an input for the PA. But in any case, the use of a P-circuit at the RA input significantly reduces the likelihood of self-excitation on VHF. By the way, this is exactly how the vast majority of PAs with OS are implemented, described in foreign literature and produced by industry for shortwave frequencies. For radio amateurs who are planning to create an RA with a power of 500 W or more, it is recommended to use lamps specially designed for linear amplification of radio frequency signals in a circuit with OK. This recommendation becomes especially relevant when using expensive “branded” transceivers - in RA with OS, during self-excitation, there is significant power of RF or microwave oscillations at the input, which can lead to failure of either the output stage or the input circuits of the transceiver (depending on switching of the RX - TX circuit at the moment of self-excitation). Alas, this is not the author’s fantasy, but real cases from practice.

And one more problem cannot be ignored when considering tube RAs - with the light hand of V. Zhalnerauskas and V. Drozdov, schemes for constructing the transmitting part of the transceiver have become popular, when, after a bandpass filter, linear amplification of the radio frequency signal by transistor stages without intermediate filtering is used to excite the tube amplifier. Structurally, the transceiver is simplified, but the price of such simplicity is an increased content of spurious emissions if such circuits are not carefully configured.

The situation gets even worse when the output power of the transceiver is not enough to “drive”, for example in the case of the GU74B with OK with a wideband input circuit on a 1:4 transformer. The required gain is usually achieved by an additional broadband stage. If a low IF is used, and after a two- or three-loop DFT, the transmitting path has a gain of 40...60 dB in power, and the P-loop is the only selective circuit of this path, then sufficient suppression of spurious emissions is not ensured. The effects can be heard on the amateur bands every day, such as second harmonics almost equal in power to the main signal. Listen, for example, to the 3680...3860 kHz section, and you will almost certainly hear second harmonic signals from SSB stations on the 160-meter range. The RA itself also has a certain nonlinearity, so even when a spectrally pure radio frequency signal is supplied to it, harmonics are inevitably present at the output. A single P-circuit can be recommended for output power up to 1 kW. At higher power, foreign amateur and industrial PAs use the P-L circuit shown in Fig. 1 - its filtration coefficient is twice as high.

Let us now consider circuit solutions that demonstrate a rather demanding approach to the design of RA.

The publication introduces us to the American version of the homemade RA on the GU74B. George T. Daughters, AB6YL, having decided to remake the Dentron MLA2500 industrial amplifier, originally built on triodes according to the OS circuit, opted for the GU74B lamp (American designation - 4СХ800А). For this project, he considered it optimal to use the mode of supplying the excitation signal to the control grid, where the input power is dissipated by a fifty-ohm resistor between the grid and the common wire. This eliminated the need for customized input circuits and easily provided broadband. The low impedance of the control grid circuit helps avoid self-excitation and provides the transceiver's output stage with a stable resistive load with low SWR. In addition, the very popular commercial amplifier ALPHA/POWER 91B with an output power of 1500 W uses a pair of 4CX800A in this connection - this is an already proven circuit!

The amplifier circuit is shown in Fig. 2.

The large input capacitance of the 4CX800A (about 50 pF) requires the use of inductive compensation, especially in high frequency ranges. Wirewound resistor R1B 6 W/6 Ohm provides the necessary inductance and, together with non-inductive R1A and R1C, complements the load resistance to the required 50 Ohm/50 W. According to AB6YL measurements, at frequencies below 35 MHz the input SWR is less than 1.1.

The energy performance of the amplifier can be improved by connecting a non-inductive resistor R2 with a resistance of up to 30 Ohms between the cathode and the common wire. This resistor provides negative feedback, which reduces the quiescent current and slightly improves linearity; the level of fifth-order components decreases by approximately 3 dB.

The parameters of the P-circuit are not given, because Components from Dentron - MLA2500 were used.

The 4СХ800А filament must be turned on at least 2.5 minutes before the excitation and supply voltages are applied.

Specifications for 4СХ800А/ГУ74Б, supplied to the American market, recommend a bias voltage on the control grid of about -56 V with a screen voltage of +350 V. The control grid power supply consists of a low-power transformer T2, connected in reverse - to the secondary winding, used as the primary, A voltage of 6.3 V is supplied from the main transformer T1, which provides about 60 V AC voltage. At the output of the parametric stabilizer VD9, R12 there is a voltage of -56 V. Any control grid current causes nonlinear distortion leading to splatter. The grid current detector is assembled on an operational amplifier DA1, connected according to a comparator circuit. When the grid current exceeds a few milliamps, the voltage drop across R16 increases, causing the comparator to operate and the red LED to glow.

The screen grid is powered by a voltage stabilizer (VT1, VT2, VD7) with protection against excess current consumption. Relay contacts K2 switch the screen grid between the common wire (via R13) in receive mode and +350 V in transmit mode. Resistor R9 prevents voltage surges when switching the relay. The screen grid current is indicated by the PA1 pointer device, because For tetrodes, the screen grid current is a better indicator of resonance and tuning than the anode current. In transmit mode, the anode quiescent current should be 150...200 mA, while the screen grid current is about -5 mA (if a device without a zero in the middle is used, the arrow will move to the left all the way). The amplifier operates in linear mode and does not need ALC (as long as there is no control grid current) with an anode current of 550...600 mA and a screen grid current of approximately 25 mA. If the screen grid current at resonance exceeds 30 mA, it is necessary to increase the connection to the load or reduce the excitation power. When tuning tetrode amplifiers, it must be remembered that the anode current increases with increasing excitation power; The screen grid current is maximum at resonance or weak connection with the load. When adjusting the amplifier for maximum output power, you should not exceed the parameters specified in the specifications for optimal linearity. The required amplifier excitation power decreases in high frequency ranges. This is explained by the influence of the cathode-heater capacitance, which shunts resistor R2, reducing the environmental impact. This must be kept in mind to avoid over-exciting the amplifier on 15 and 10 meters. (Or use an RF choke in the filament circuit. Ed.)

The amplifier parameters with an input power of about 45 W are given in Table 1. (The output power value seems to be somewhat overestimated. Editor's note.) Before turning off the amplifier after a session, you need to leave it in the standby position for about three minutes - the fan should cool the lamp.

Table 1
Anode voltage 2200 V
Anode quiescent current 170 mA
Maximum anode current 550 mA
Screen grid current maximum 25 mA 0
Power dissipation at the anode without signal 370 W
Power supplied 1200 W
Output power 750W

Part two

The desire to provide reliable and durable performance of a highly linear power amplifier was clearly demonstrated by Mark Mandelkern, KN5S. Schematic diagrams of the amplifier and auxiliary circuits are shown in Fig. 3...8.

Do not be surprised by the abundance of semiconductor devices - their use is justified and deserves attention, especially the use of protection circuits. (However, it cannot be said that all of them are absolutely necessary. Ed.)

When designing the RA, the following goals were pursued:
- power supply of the lamp heater from a stabilized DC source; use of automatic heating and cooling timers;
- measurement of all parameters, including anode current and voltage, without inconvenient switching;
- the presence of stabilized sources of bias and screen voltage, allowing voltage adjustment within a wide range;
- ensuring operability under significant fluctuations in network voltage (this is especially true when working in the field using an electric current generator).

The power source for the heater of powerful generator lamps is rarely given due attention, but it largely determines the longevity of the lamp and the stability of the output power. Warming up of the heater should occur gradually, avoiding current surges through the cold filament. In transmission mode, when intense electron emission occurs, it is very important to ensure a constant filament voltage and, accordingly, a constant cathode temperature. These are the main reasons for using a stabilized power source with a current limiter for incandescent lamps, which eliminates the current surge at the moment of switching on.

The power supply diagram is shown in Fig. 4. The output voltages allow the following adjustment ranges: from 5.5 to 6 V (filament), from 200 to 350 V (screen grid) and from -25 to -125 V (control grid).

The filament voltage stabilizer uses the popular LN723 microcircuit in a typical connection. The significant filament current of the 4CX1000 tetrode (about 9 A) and the connection of the cathode and heater inside the lamp required separate large-section conductors for the high-current circuit (A- and A+); Through the S- and S+ circuit, the output voltage is supplied to the stabilizer comparison circuit. It is best to solder the FU1 10 A fuse rather than use a fuse holder.

The heater control circuit is shown in Fig. 5. The circuit eliminates the use of the amplifier during warm-up and protects the heater from increased voltage if the stabilizer malfunctions. Protection is provided by turning off the heater using relay K2 (Fig. 4). In addition, the air flow sensor through the lamp SA2 (Fig. 4) monitors the performance of the fan. If there is no air flow, this will also cause relay K2 and the filament voltage regulator to turn off.

The warm-up timer (DA3 in Fig. 5) is set to five minutes. According to the specifications, three minutes is enough, but longer heating will extend the life of the lamp. The timer starts only after voltage appears on the heater. This is determined by the comparator DA2.2 connected to point S+. So, for example, if a fuse is blown, the timer will not start until you replace the fuse. When the voltage is exceeded (for example, when the control transistor VT1 breaks down), the trigger on DA2.3 is activated and the transistor VT2 closes, disconnecting the voltage from the winding of relay K2 (point HR in Fig. 5). Capacitor SZ ensures the initial setting of the trigger and, accordingly, the opening of transistor VT2 when the supply voltage is applied.

Along with the warm-up timer, the amplifier needs a timer for the tube to cool down before turning off (DA4). When the amplifier is turned off, the +12 V circuit discharges faster than the +24 V circuit (which has a minimum load in receive mode). A voltage of +24 V appears at the DA2.1 output and the cooling timer starts. After startup, there is a low voltage level at pin 7 of DA4, which triggers relay K1 (Fig. 4), through the contacts of which the operation of the +12/-12 V and +24 V stabilizers is ensured. After approximately three minutes, a high level appears at pin 7, relay K1 returns to its original state, and the amplifier is finally de-energized. The +24 RLY circuit eliminates the operation of the cooling timer if for some reason the amplifier was turned off and immediately turned on. For example, the passage of radio waves ends and the range seems dead - you turn off the amplifier. Suddenly an interesting correspondent appears - the power switch is again in the ON position! When entering transmit mode, the +24RLY voltage forces DA2.1 to a low state and resets the cooling timer.

As in the case of filament voltage, the screen grid voltage stabilizer rarely receives attention when designing a PA. But in vain... Powerful tetrodes, due to the phenomenon of secondary emission, have a negative screen grid current, so the power source of this circuit must not only supply current to the load, but also consume it when the direction changes. Series stabilizer circuits do not provide this, and when a negative screen grid current appears, the series stabilizer transistor may fail. Having lost several high-voltage transistors when setting up the amplifier, radio amateurs come to the decision to install a powerful resistor with a resistance of 5...15 kOhm between the screen grid and the common wire, resigning themselves to useless power dissipation. The use of a parallel voltage stabilizer, which can not only supply, but also receive current, allows for trouble-free operation, but it is advisable to use overcurrent protection.

The screen grid voltage stabilizer is assembled using transistors VT3, VT4 (Fig. 4). Instead of VT3 type 2N2222A, you can use a high-voltage one, excluding the parametric stabilizer R6, VD5, but in this case the stabilization coefficient may deteriorate, because high-voltage transistors have low gain. The output voltage is determined by the sum of the stabilization voltage VD11 and the voltage at the base-emitter junctions of transistors VT3, VT4 (15+0.6+0.6=16.2 V), multiplied by the coefficient determined by the voltage divider R11,R12,R13 (12. ..20) at the output of the stabilizer.

The shunt transistor is mounted directly on an aluminum plate measuring 70x100x5 mm, which, in turn, is mounted on the side wall using ceramic insulators. Resistor R7 limits the peak current through shunt transistor VT4 to about 100 mA.

The RECEPTION-TRANSMIT circuit (Fig. 6) checks six signals: the presence of air flow through the lamp (+12N), the state of the OPERATE-STANDBY switch, the completion of filament heating, the presence of anode voltage, the presence of bias voltage and the state of the overload protection circuit. The reception-transmission switching circuit provides a delay in the operation of the short-circuit relay of 50 ms (Fig. 4) when switching to transmission and a delay in turning off the coaxial relay of 15 ms when switching to reception. If vacuum relays are used, the relay timing can be easily changed for full QSK.

The op-amps of the receive-transmit switching circuit in Fig. 6 use very simple R-C networks to obtain the switching delay. In transmit mode, there is a voltage of about +11 V at the output of DA1.4, which provides a quick charge of capacitor C4 through the diode VD8 of the Kant antenna switching coaxial relay circuit. Capacitor C5 of the screen grid power relay circuit is charged through resistor R26, so the screen relay operates later. When switching to receive mode, a voltage of about -11 V appears at the DA1.4 output, and the reverse process occurs. The KEY input allows you to reduce power dissipation at the anode during transmission pauses and avoid changing the shape of the CW signal sent when working with PA, but for this it is necessary that the transceiver has an appropriate output. The overload blocking circuit (Fig. 7) is triggered when the control or screen grid or anode current exceeds 1 mA, -30 mA and 1150 mA, respectively. The screen grid overload protection circuit operates only at negative currents. The positive current limiter of the screen grid is resistor R27 in the voltage stabilizer circuit. Triggering of the overload protection circuit (Fig. 8) causes the TRANSMISSION circuit to be turned off via the OL circuit (Fig. 6), the additional resistor R2 in the control grid bias circuit is turned on using relay contacts K1, the generator on DA2.4 is turned on and the red LED flashes VD9 OVERLOAD on the front panel.

Only the DA2 microcircuit is powered from a unipolar +24 V source (Fig. 5). All other op amps use +12/-12 V supply voltage.

Figure 7 shows the measurement diagram. Five pointer instruments allow you to measure 10(!) parameters using additional buttons: direct/reflected power in the antenna, control grid current/voltage, anode current/voltage, screen grid current/voltage, filament voltage/current. To read the parameter values indicated through a fraction, you must press the corresponding button. Basic parameters are read immediately; Secondary parameters are of great importance only for the initial setup and for adjustments after replacing the lamp. The simplest non-inverting amplifier used here is to measure the anode voltage (DA2.1). Let us assume that the measurement limit should be 5000 V; The divider R7, R8 (Fig. 3) has a division coefficient of 10,000, i.e. 5000 V at point HV2 is 0.5 V. Resistor R9 does not affect the operation of the circuit since the op-amp has a high input impedance. With a supply voltage of +12/-12 V, the maximum output voltage of the amplifier is about +11/-11 V. Let us assume that +10 V of the output voltage of the operational amplifier corresponds to the full deflection of the meter needle when using a 10 kOhm resistor R22 and a 1 mA device. The required gain (10/0.5) is 20. Having chosen R15 = 10k0m, we find that the feedback resistor should have a resistance of 190 kOhm. The specified resistor is composed of a trimming resistor R20 with a resistance of approximately half the nominal value and a constant resistor R19, selected from a number of standard values.

The anode current measurement circuit is similar. A voltage proportional to the anode current is removed from the negative feedback resistor R2 in the cathode circuit (Fig. 3). Capacitor C2 provides damping of the readings of the measuring device ONCE during SSB operation.

Screen voltage is measured in a similar way. The values of the resistors that determine the gain of the forward and reverse power measurement circuits depend on the design of the directional coupler.

The screen grid current measurement circuit is implemented somewhat differently. It was indicated above that the screen grid current can have both negative and positive values, i.e. a measuring device with a zero in the middle is required. The circuit is implemented on a DA2.3 operational amplifier and has a measurement range of -50...0...50 mA, using a conventional device with a zero on the left for indication.

At 50 mA positive screen grid current, the voltage drop across resistor R23 (Fig. 4) is -5V at point -E2. Thus, a gain of -1 is required from the op amp to produce the required +5V output voltage to deflect the needle by half scale. When R23=10 kOhm, the feedback resistor should have a nominal value of 10 kOhm; tuning resistors R32 and constant resistors R30 are used. To shift the instrument needle to the middle of the scale at a supply voltage of -12 V, a gain of +5/-12=-0.417 is required. The exact value of the gain and, accordingly, the zero of the scale is set by trimming resistor R25.

Operational amplifiers DA2.2, DA2.4 have an extended filament voltage measurement scale. The differential amplifier DA2.2 converts the filament voltage to unipolar, because point S is not directly connected to the common wire. The DA2.4 summing amplifier implements an extended measurement scale - from 5.0 to 6.0 V. In fact, it is a voltmeter with a measurement limit of 1 V, biased to the initial value of 5 V.

In rectifier circuits, the diodes used must be designed for the appropriate current, the rest - any pulsed silicon diodes. With the exception of high-voltage transistors, any low-power corresponding structure can be used. Operational amplifiers - LM324 or similar. Measuring instruments - PA1...PA5 with a total deviation current of 1 mA.

The above schemes certainly complicate RA. But for reliable everyday work on air and in competitions, it’s worth spending extra effort on creating a truly high-quality device. If there are more clean and loud signals on the bands, then all radio amateurs will benefit. For QRO without QRM! I express my gratitude to I. Goncharenko (EU1TT), whose advice and comments were of great help when working on the article.

Literature

1. Bunimovich S., Yailenko L. Amateur single-sideband radio communication technology. - Moscow, DOSAAF, 1970.
2. Radio, 1986, N4, P.20.
3. Drozdov V. Amateur KB transceivers. - Moscow, Radio and Communications, 1988.
4. QST ON CD-ROM, 1996, N5.
5. http: //www.svetlana.com/.
6. QEX ON CD-ROM, 1996, N5.
7. QEX ON CD-ROM, 1996, N11.
8. Radio amateur. KB and UKV, 1998, N2, P.24.
9. Radio Amateur, 1992, N6, P.38.
10. ALPHA/POWER ETO 91B User's Manual.

G.LIVER (EW1EA) "HF and VHF" No. 9 1998

From the practice of designing tube HF amplifiers

Probably every radio amateur, especially those working on the low frequency bands, would like to have a compact power amplifier, with good efficiency, compatible with modern HF transceivers, now, as a rule, imported, with a decent appearance that would decorate and give solidity to our radio sheks, and , most importantly, it was highly reliable and pleased with its work.

Where - where, and thank God we in Russia have such excellent and quite affordable radio tubes as GU 50, GI 7 B, GMI 11, GU 46, GU 43 B, GU 91 B, GU 78 B, etc. , which are valued all over the world. After all, if you properly prepare a radio lamp for operation, even if it has lain idle for decades, and comply with the necessary requirements and operating modes, then one such lamp will last for many years. Failure of a radio tube due to static or surges in the supply network is unlikely with a reasonable circuit design; the radio tube is not afraid of mismatch and prolonged overheating and overloads.

When developing an output stage, there is no need to play it safe and use transformers in power supplies, filter capacitors and other radio elements that exceed the required values in power, capacity and size, otherwise it will look like a bicycle with truck wheels. Instead of the expected high parameters, reliability will decrease, especially when high-voltage sources are turned on and in the first seconds of warming up the filament of radio tubes. The design must be based on a reasonable compromise that takes into account all sides; only then is it possible to achieve high reliability, the required parameters, dimensions and weight.

If, for some reason, such radio elements are used, then you will have to complicate the circuit and use devices that smooth out extra currents, use a time delay relay, and protect the computer from surges in the network if it is used. But we must always remember that every extra contact, every extra semiconductor is an element of unreliability, especially in the output stage.

I would like to dwell on the power supply circuits of radio tubes. It is necessary to select the correct voltage from the wide tolerance specified in the passport, which ensures long-term operation of the radio tube; not every standardized transformer is suitable for this.

Now there are many diodes with excellent parameters, and RF elements of the output stages of military radio stations: coils; panels for lamps; KPIs, including vacuum ones, with excellent overlap; switches; relay V2V, P1D, etc. This is of course the ultimate dream. If you approach this wisely and do not put a coil of a 20 x 3 bus in a cascade on the GU 82B, then you can get quite acceptable dimensions. It is convenient to use two-block designs when the power source is located under the table, then the output stage itself will be more compact.

Low-current relays, including reed switches, easily provide control of the main contactors of the amplifier and interface with the transceiver, both for switching bands and for controlling reception/transmission.

When designing a cascade, it is important to know whether it will be used in contests, operated in FM, CW, etc. modes, or whether the cascade is intended purely for everyday amateur radio communication. All this affects weight, dimensions, and airflow modes. The correct choice of switching circuit for a radio tube with a common cathode or a common grid can help out, this is very important!!!

Such modes are undesirable when three 50 GUs receive 500 W in the antenna; in this case, you will have to have a supply of lamps. There is no point in this, because there are more powerful lamps, and even more so, for example, if you had a power of 300 W, and you increased it to 500, then almost no one will notice this increase of 2 db (0.3 points). will notice.

It is not superfluous to install at least LEDs on the front panel that control the grid currents and indicate the operation of the cascade in the appropriate modes.

The scheme with parallel power supply to the anode circuit, beloved by many designers, justifies itself when using lamps with a small output capacitance and the initial capacity of the anode KPI, but it also has its own difficulties - the anode choke must be correctly configured, it is important to know its resonant frequency, which can be determined using an RF voltmeter . The resonant frequency of the choke should not be near the amateur radio ranges. It is advisable to stipulate somewhere a ban on transmission at this frequency, otherwise with modern transceivers with continuous overlap up to 30 MHz, turning the knobs of the encoder to the resonant frequency of the choke can damage the power amplifier.

If the PA uses a lamp with a large output capacitance of tens of pF, type GU 81, and at a high anode voltage, increasing Re or using a KPI with a large initial capacitance, it is advisable to use a circuit with a series supply of the anode circuit, and use incomplete inclusion of the elements of the oscillatory system. In front of the output stage tuning controls, it is necessary to install high-quality high-capacity RF capacitors with a voltage of at least twice the anode voltage, in order to remove the DC component and, at the same time, not reduce the capacity of the control unit. The range switch in such a circuit is subject to increased requirements, since it is under high voltage and must be reliably isolated from the housing, and the axis of the control knob is separated by a dielectric RF insert.

Based on many years of observations, I can’t say anything negative about the use of low power in PAs - up to 1 KW of electrolytic capacitors in anode voltage sources. It is only necessary to ensure that the voltage on each capacitor is no more than 85% of the voltage indicated on the capacitor body, and try not to place electrolytic capacitors near the heating elements of the cascade. There have been cases of failure of capacitors of type K 50-17 1000uF/400V, etc., where the output copper terminals have aluminum rivets - over time, naturally, the contact is broken. It is clear that in more powerful output stages, the use of metal-paper and combined type capacitors (K 75) is preferable.

It is clear that it is difficult to specify all the subtleties, but if at least these points are taken into account, the cascade will work reliably, linearly, without expanding the bands, and without creating out-of-band emissions. Surely many radio amateurs do it all this way. But the normal operation of even such a cascade can easily be ruined by increasing the signal level from the transceiver beyond normal or by distorting the input signal by excessive compression and overload at the microphone input.

As in any business, one should not expect quick results and the first dozen designs will not be entirely successful, for example: not the optimal ratio of dimensions, weight, output power, design in general, operation of cooling systems, location of controls and controls, ease of use , reliability of the cascade during fluctuations in the supply network, elevated temperatures, operation with non-standard loads, etc. But with years of observation, analysis, work on mistakes and, of course, daily work, something will probably start to work out.

Now a little about psychological aspects. You can hear the following reasoning: “Before I had a UM on GU 71, this is a thing, but now on GU 13 no one hears me.” This is, of course, funny, but a person has such a misconception ingrained in him, it is difficult for him to prove that this is the same thing, and that this is from the area “when the trees were big.” Do not believe these sometimes pleasant memories and impressions, but only believe the power meter needle at the output of your stage. I naturally omit all talk about antennas and transmission, as a matter of course and playing an important role.

I would like to make the following observations:

if you doubled the power, for example, from 100 to 200 W, then almost no one will notice it, but they will say: “Probably QSB”;
if you increased the power 4 times, you received an increase of 1 point (6 db), but not everyone will pay attention to this, but only an experienced correspondent;
an increase in power by 10 times more than 1.5 points (10 db) is noticed by almost everyone, although estimates can range from 3 to 20 db;
16 times – 2 points (12 db), give credit to the work of the output stage;
an increase in power by 64 times is 3 points (18db), comments are unnecessary, and estimates can range from 10 to 40 db.

Such experiments must be carried out very quickly, to minimize the influence of QSB, clearly indicate the positions and be sure to monitor the matching and the actual output to the antenna every time it is turned on.

This must be taken into account in order not to place unreasonable hopes on one or another output stage, but to realistically evaluate its capabilities and imagine what effect it will have.

More details can be found at: www.afaru.ru/rz3ah

A. ROGOV ( RZ3AH)
Moscow tel. 909–50–13

Tube HF power amplifier. What should a power amplifier for an amateur HF radio station be like? HF transformers for HF amplifiers for amateur radio operators

Part one

Part two

Literature

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