Linear amplifier on gk 71. Feeding the filament of a powerful generator lamp

The power amplifier (PA) is made on the "old" reliable GK71 lamp, with a graphite anode that does not require airflow. circuit diagram shown in fig. one.

The scheme is classical with a common grid (OS). Anode voltage - 3 kV, screen grid voltage - +50 V, filament voltage - 22 V, in "Sleep mode" - 11 V. Quiescent current - 100 mA. The buildup power Rvx is 50-80 watts.

Power delivered to a load equivalent of 50 ohms Pout = 500-700 W.

The features of this UM scheme are:

the introduction of a protection circuit against overcurrent and short circuit (short circuit) and the maintenance of "Sleep mode" in the MIND;
the use of a cathode resonant circuit for better matching with imported transceivers;
the original P-loop circuit, which allows you to get the same output power on all ranges.

Rice. 1. Schematic diagram of the GK71 power amplifier with a common grid.

The PA is powered by one powerful transformer made on a torus. A high anode voltage of 2.5-3.0 kV is obtained by doubling the voltage taken from the step-up winding of the transformer.

When the PA is turned on, the mains voltage of 220 V, passing through the mains filter Lf, C42, C43, SA4 circuit breaker, is supplied to the primary winding of the transformer through halogen lamp HL1. This provides a “soft” start and extends the life of the VL1 GK71 lamp and other PA elements.

After the capacitors are charged, part of the high voltage taken from the divider R13-R18 and the potentiometer R12 is fed to the automation circuit, made on a transistor? ТЗ. If there is no short circuit in the PA circuit, the voltage is normal, then? TZ opens, relay Kb is activated, closing the halogen lamp HL1 with its contacts K6.1.

A feature of this automation scheme is the "small hysteresis" of actuation / release of Kb. This provides reliable protection of the PA from overcurrent of the anode or short circuit in the secondary circuits, breakdown and short circuit in the transformer windings, at which?

In standby mode, an incomplete 11V glow voltage is supplied to the GK71 lamp. This ensures low heating of the lamp, the PA as a whole and the “Sleep Mode” of the PA. When switching to "TX", the full filament voltage of 22 V is applied to the GK71, and already after 0.2-0.25 s, the PA is ready to operate at full power, which is the undoubted advantage of direct filament lamps GK71, GU13, GU81.

To fully match the PA with imported transceivers, a “Cathode Circuit” is used, which is tuned to resonance on each range by connecting capacitors to L1 using the K9-K13 relay on the 10-24 MHz bands.

Initially, the L1 circuit is tuned to the 28 MHz range by the capacitor C21. On the low frequency ranges of 3.5 and 7 MHz, for more complete matching (due to the narrow band of the L1C cathode circuit), the signal is fed through the contacts of the K7 relay to the cathode three-winding choke - Dr1. At the same time, to exclude the influence of L1, it is short-circuited by the RF capacitor C14 through contacts K8.1.

The SWR at the PA input does not exceed 1.5 on all bands and is in good agreement with any imported transceiver, even without a tuner.

The output P-circuit of the PA is switched by a 3-way switch SA1. SA1.3 - switches the taps of the coils and connects an additional capacitor C23 to the KPI C22 connection with the antenna on the 3.5 MHz band.

Switch SA1.2 shorts the 3.5MHz coil. Switch SA1.1 switches range relays. If a 1.8 MHz band is planned, then you need to add another relay and use the 9th position on the SA1 switch.

The L4 coil operates on the 28 MHz range, which is located directly in the GK71 anode circuit. This made it possible to obtain Pout at 28 MHz the same as on the low bands. Dr3 is necessary to protect the output circuits of the PA.

The “RX / TX” control is carried out by the circuit on the transistor VT1, which is powered by a voltage of +24 V. When the RX / TX input of the XS1 connector of pin 3 is closed to the case (current 3-5 mA), the circuit on the transistor? T1 opens, the short circuit relay is activated and through contacts K3.1, +24 V is supplied to relays K1 and K2. The K4 relay is activated, supplying the full glow voltage to the GK71 through contacts K4.1.

If the SA3 "Glow" switch is on, the full glow voltage is constantly applied to the VL1 lamp. This may be necessary when working in TESTax. After charging the capacitor C3 (after 0.15-0.2 s), relay K5 will operate, which provides:

correct operation of the UM;
no burning of relay contacts K1, K2.

Relay K5 with contacts K5.1 closes the circuit of the control grid of the VL1 lamp to the housing, opening it. To implement the “Bypass” mode, the SA2 switch breaks the +24 V supply circuit of the circuit on? T1 of the “RX / TX” switch. On the transistor? T2, an adjustable voltage regulator of the screen grid of the lamp VL1 is made.

Potentiometer R4 sets the quiescent current VL1 in the range of 100-120 mA. On the DA1 chip, a +24 V voltage regulator is made to power the relay and the automation circuit. In case of overloads and short circuits at +24 V, DA1 automatically turns off, which also increases the reliability of the PA as a whole.

Power amplifier design

UM is made in the case system block computer, preferably an old model of the 80s - it is made of thicker steel. Dimensions 175x325x400 mm. The vertical partition and horizontal shelves are made of steel 1.5-2 mm thick.

With intensive work of the PA, it is desirable to use a fan operating at a reduced supply voltage to reduce noise.

Parts and possible replacements

Transformer T1 is made on iron from LATR-8 10 A. The network winding is wound with PEL wire 1.5 mm. Step-up winding PEL 0.65-0.7 mm, voltage 1.1-1.2 kV. Filament winding PEL 1.5 mm 11 + 11 V, other PEL windings 0.5-0.65 mm for voltages of 22 V and 50 V.

Circuit breaker SA4 type VA-47 for 10 A. The cathode choke Dr1 is wound on a ferrite ring K45x27x15 mm 2000NN in two wires 1.2-1.5 mm and contains 12 turns. The communication coil has 7 turns of MGTF0.2 mm wire, evenly distributed between the turns of the main winding.

Coil L1 of the cathode circuit is made of a copper tube with a diameter of 5-6 mm. Inside which a wire is stretched in heat-resistant insulation MGTF, BPVL with a cross section of at least 1 mm2. The outer diameter of the coil is 27-30 mm, the gap between the turns is 0.2-0.3 mm and contains 8 turns, tapped from the middle.

The L2 coil of the 3.5-7 MHz range is made on a frame with a diameter of 40-45 mm and contains 15 + 12 turns of wire 1.5-2.0 mm. The first 15 turns for the 3.5 MHz band are wound turn to turn, and the remaining 12 turns in 2.5 mm increments.

The L3 coil of the 10-21 MHz range is made of a copper tube with a diameter of 5-6 mm and contains 15-17 turns, the outer diameter is 50-55 mm.

The L4 coil of the 28 MHz range is made of copper wire with a diameter of 2.0-2.5 mm and contains 5-6 turns, the outer diameter of the coil is 25 mm.

The anode choke Dr2 is wound on a PTFE frame with a diameter of 18-20 mm, a length of 180 mm, a PELSHO wire of 0.35 mm, a turn to turn in sections of 41 + 34 + 32 + 29 + 27 + 20 + 17 + 11 turns and the last 10 turns in discharge in 2 mm increments.

Dr3 - winding station wagon with PELSHO wire 0.2-0.3 mm 2-4 sections of 80-100 turns.

The mains filter Lf is wound on a K45x27x15 mm 2000NN ring in two wires with a diameter of 1 mm, with good insulation of the MGTF type, turn to turn until filled.

Anode KPE C24 from UHF-66. One section, gap 2.5-2.7 mm 15-100 pF, connected to the 2nd turn of the L3 coil. Capacitor C23 - connection with the antenna KPI 2-3 sections from old radios with a gap of 0.3-0.4 mm, 30-1200 pF.

Relay K1 - REN-33, K2 - REN-34. Relays KZ-K6 - small-sized imported plastic cases 15x15x20 mm, switching current 6-8 A, switching voltage 127-220 V. Relays KZ and Kb for an operating voltage of 24 V, and relays K4 and K5 for an operating voltage of 12 V. Relay K7 -K13 - RES-10 low-power silicon diodes are connected in parallel with the relay windings. Diodes are not shown in the diagram.

Transistors VT1 - KT835, KT837. VT2, VT3 - KT829A. DA1 - KR142EN-9 (B, D) or MC7824.

power amplifier on a GK71 lamp

V. Fedorchenko, rz3tl, Dzerzhinsk.--------

The power amplifier is made on a GK71 lamp - time-tested, reliable, with graphite anodes that do not require forced cooling. The amplifier circuit is classic, with a common grid. Anode voltage - 3 kV, screen grid - 50 V, glow - 22 V (in "sleep" mode - 11 V), quiescent current - 60 mA. With an excitation power of 50-80 W, the amplifier provides an output power of 500-600 W at a 50-ohm load.

The features of the amplifier circuit are protection against overcurrent and short circuit, as well as a "sleep" mode. To better match with imported transceivers, a resonant circuit is used in the input part of the amplifier, and to achieve a constant output power on all ranges, an original P-circuit circuit is used.

The amplifier is powered by one powerful power transformer, made on a toroidal core. High anode voltage (2.5-3.0 kV) is obtained after rectifying-doubling the voltage taken from the step-up winding of the power transformer.

When the amplifier is turned on, the mains voltage of 220 V passes through the S43-Dr5-S44 surge protector, circuit breaker sf 1 and is fed to the primary winding of the power transformer through a halogen lamp vl 3, which provides a "soft" turn on of the amplifier, extending the life of the GK71 lamp and other circuit elements. After chargecapacitors part of the high voltage taken from the divider r 8- r 13 and potentiometer r 14, fed to the automation circuit on a transistor vt 3. If there is no short circuit in the high voltage circuit, and the voltage is normal, then the transistor vt 3 opens, relay K4 is activated, closing the lamp with its contacts vl 3 and supplying the full AC voltage to the primary winding of the transformer.

A feature of this automation circuit is the small hysteresis of the operation and release of the K4 relay, which provides reliable protection of the amplifier from various overloads - by anode current, during short circuits in secondary circuits, breakdown and short circuit in the windings of a power transformer. In the event of these malfunctions, the transistor vt 3 closes, relay K4 is de-energized, and the mains winding of the power transformer is connected to the AC mains through the lamp vl 3, which prevents failure of the amplifier elements.

In standby mode, an incomplete glow voltage (11 V) is supplied to the GK-71 lamp. This ensures low heating of the lamp and the amplifier as a whole, i.e. "sleep mode". When switching to the transmission mode (TX), the full filament voltage (22 V) is applied to the GK71 cathode, and already after 0.2-0.25 s the amplifier is ready to operate at full power. This is the undoubted advantage of direct incandescent lamps GK71, GU 13, GU81 and others.

To more fully match the amplifier with imported transceivers, a "cathode" circuit is used, tuned to resonance in the ranges of 7-28 MHz. When operating in the 28 MHz band, the circuit is formed by a coil l 3, made of a copper tube (its design is described below), and capacitor C22, and to obtain resonance in the lower frequency ranges of 7-24 MHz, capacitors C11-C16 are connected to this circuit.

On the low bands of 1.8 and 3.5 MHz, the "cathode" circuit is rather narrow-band, therefore, in order to better match the transceiver with the amplifier, a broadband transformer T1 is used instead of the circuit, to which the input signal is fed through the contacts of the relay K9. At the same time, in order to exclude the influence on HF, the coil l 3 "short-circuited" through the capacitor C17 and through the contacts K11.1.

On all ranges, the SWR at the input of the amplifier does not exceed 1.5, which provides excellent (or) matching of the amplifier with any imported transceiver, even without a built-in antenna tuner.

The output P-circuit of the amplifier is switched by a three-switch switch: biscuit sa 4.1 switches coil taps l 2 and connects additional capacitors C6 and C9 to the "antenna" KPI in the 1.8 and 3.5 MHz bands, sa 4.2 shorts the coil l 1 1.8 MHz band (or 3.5 MHz if 1.8 MHz band is not used), sa 4.3 connects range relays K8-K13, through the contacts of which capacitors C11-C16 and auxiliary relays Kb and K7 are connected to the "cathode" circuit.

When operating in the 28 MHz band, a coil is used l 4, which is installed directly in the anode circuit of the GK71 lamp. Such an implementation of the P-loop made it possible to obtain an output power of at least 500 W in this range (as in the low bands!). Inductor Dr1 is necessary to protect the output circuits of the amplifier.

Receive/transmit control(rx/tx) implements a transistor circuit vt 1, which is powered by a voltage of +24 V. When the "TX" input is closed to a common wire (the current in this circuit is 3-5 mA), the transistor opens vt 1 , relays K1 (switching the input RF circuits of the amplifier), K2 (switching the output circuits of the amplifier) and K5 (supplying the full glow voltage to the GK71 cathode) are triggered. If the switch sa 2 is set to the lower (according to the diagram) position, then the full filament voltage is supplied to the GK71 lamp constantly, which is necessary when working in competitions.

After charging the capacitor C45 (after 0.15-0.2 s), the short-circuit relay is activated and with its contacts K3.1 closes the circuit of the first grid of the lamp vl 1 to a common wire. The lamp opens and goes into amplifying mode. Such a circuitry solution ensures the correct operation of the amplifier and the absence of burning of the relay contacts K1 and K2.

To facilitate the thermal regime of the amplifier, a computer fan (12 V / 0.15 A) is installed, which mainly operates at a reduced (7-8 V) voltage, providing silent air boost. The fan control circuit is made on a transistor vt 4. When the amplifier goes into transmission mode through an open transistor vt 1 and resistor r 39 Capacitor C49 begins to charge. After 4-5 seconds, the transistor opens vt 4, and the fan starts to work at high speeds, because. a voltage of about 12 V is applied to it, which is set by selecting the resistances of the resistors r41 and r42 and depends on the fan type. After switching to the receive mode, due to the slow discharge of the C49 capacitor, the enhanced airflow is maintained for another 40-50 s, providing intensive cooling of the amplifier.

When switched on for a short time in the transmission mode, the fan operates at a reduced supply voltage, without creating unnecessary acoustic noise. If another fan is used, then it is possible in the collector circuit vt 4 put a 24-volt relay, the contacts of which will switch the fan operation mode.

In "Bypass" mode using the switch sa 1 the supply voltage is removed from the circuit on the transistor vt 1 , which prevents the amplifier from switching to transmission mode when a control signal is received at the "TX" connector.

On transistor vt 2 an adjustable voltage regulator of the screen grid is made. With a variable resistor r18 set the lamp quiescent current vl 1 within 50-60 mA.

+24 V voltage source based on integrated stabilizer da 1 used to power relays and automation circuits. In case of overloads and a short circuit in the +24 V circuit, the integrated stabilizer automatically turns off, which increases the reliability of the amplifier as a whole.

The amplifier uses a power transformer made on iron from a 9-ampere LATR. Iron dimensions - 130x75x75mm. The primary (network) winding contains 230 turns of wire 01.5 mm, but if the PA is operated in everyday, and not in contest mode, then you can leave the "native" primary winding of the LATR. The step-up winding should contain 1200 turns of wire 00.65-0.7 mm (alternating voltage - 1.1-1.2 kV), the filament winding - 11 + 11 turns of wire 01.5 mm (voltage - 11 + 11 V ), the remaining windings -14 + 35 turns of wire 00.5-0.65 mm (voltage - 22 and 50 V).

Broadband transformer T1 is wound with wire 01.2-1.5 mm in two wires on a ferrite ring K45x27x15 mm with a permeability of 2000NN and contains 12 turns, the coupling coil - 7 turns of MGTF-0.2 wire, evenly distributed between the turns of the main winding.

Coil l 1 wound on a frame 040-45 mm and contains 15 + 12 turns of wire 01.5-2.0 mm. The first 15 turns are wound turn to turn (for the 1.8 MHz band), and the remaining 12 are wound in 2.5 mm increments.

Coil l 2 wound with a copper tube 04-5 mm and contains 15-17 turns, the outer diameter is 50-55 mm.

Coil l 3 cathode" circuit is made of a copper tube with a diameter of 4-5 mm, inside which a wire is stretched in heat-resistant insulation (MGTF, BPVL, etc.) with a cross section of at least 0.7 mm 2. The outer diameter of the coil is 27-30 mm, the gap between turns - 0.3 mm, number of turns - 8, tap - from the middle.

Coil l 4 made of copper winding wire 02.0-2.5 mm and contains 5-6 turns, the outer diameter of the coil is 25 mm.

Choke Dr1 (winding "Universal") is wound with wire 00.2-0.3 mm and consists of 2-4 sections of 80-100 turns each; anode choke Dr2 - with PELSHO-0.35 wire on a fluoroplastic frame with a diameter of 18-20 mm and a length of 180 mm. Winding - turn to turn, in sections of 41, 34,32,29,27, 20, 17 and 11 turns, and the last 10 turns - in a discharge, with a step of 2 mm.

The anode variable capacitor C18 is from UHF-66 (one section is used), the gap between the plates is 2.5-2.7 mm, the capacitance is 15-100 pF. The left (according to the diagram) output of the capacitor is connected to the 1-2nd turn of the coil l 2.

Antenna capacitor of variable capacitance C7 - 2-3-section, from old radios, the gap between the plates is 0.3-0.4 mm, the capacitance is 30-1200 pF.

Relay K1 - REN-33, K2 - REN-34; KZ-K5 - imported, small-sized (15x15x20 mm, in plastic cases) for an operating voltage of 12 V, switching current - 6-8 A for a voltage of 125-220 V; Kb-K13 - RES-10. Relay for connecting additional capacitors to the anode capacitor 220 pF (1.8 MHz) and 150 pF (3.5 MHz) - type TORN.

Halogen lamp vl 3 - 150 W/ 220 V. Transistor vt 1 - KT835 (KT837), vt 2 - vt 4 - KT829A. Chip da 1 - KR142EN9I (78l 24).

Design

The power amplifier is made in a computer case (preferably an old one, manufactured in the 80s, made of thick steel). Overall dimensions - 175 mm (width), 325 mm (height) and 400 mm (depth). Vertical partition and horizontal shelves: - steel, 1.5-2 mm thick. In the middle (along the center line) in the P-circuit compartment and under the GK71 panel, a copper strip 10-12 mm wide and 0.2-0.3 mm thick is laid, which is connected to the "Case" terminal on the rear panel.

The mains filter is made on a separate board installed near the VA-47 machine and the "Network" connector. Between the power transformer and the vertical partition, a board of high-voltage rectifiers, stabilizers and automation is vertically installed, which is attached to the bottom of the case on an aluminum corner, which also serves as a radiator for the stabilizer da 1, vt 1 and vt 2.

On the front panel, from the inside, there are fixed: a voltage indication board for the control and screen grids, a high voltage and a halogen lamp, and its glow should be visible through the hole (a 03 mm red filter is laid) located near the "Anode" toggle switch.

At the range switch, the extreme board switching the coil taps is additionally isolated from the fastening screws with fluoroplastic bushings to increase reliability.

On the measuring device, right on its terminals, a board for measuring the output RF voltage is fixed.

Setting

First, without applying voltage from the step-up winding to the high-voltage rectifier, they check for the presence of filament voltage, relay power (+24 V), locking the GK71 lamp (-60-70 V) and screen grid power (+1-55 V); fan operating modes(rx - 7-8 V, TX - 10-12 V), as well as the operation of the switching unit"rx/tx".

Next, connect the high-voltage winding to the rectifier. At idle, the constant anode voltage should be 2.8-3 kV. resistor resistance adjustment r14 set a clear operation of relay K4 at a mains voltage of 200 V.

Then by adjusting the resistance of the resistor r1 8 in the TX mode, the quiescent current of the GK71 lamp is set within 50-60 mA.

The RF amplifier tuning starts from the "cathode" circuit. In the transmission mode from the transceiver (with the antenna tuner turned off), a signal with a power of 5-10 W is supplied and the SWR is adjusted to a minimum, focusing on the readings of the SWR meter of the transceiver. In the 28 MHz range, the "cathode" circuit is adjusted by adjusting the capacitance of the capacitor C22. Then, by adjusting the capacitances of capacitors C13-C16 and selecting the capacitance of capacitors C11 and C12, this circuit is tuned to the lower frequency ranges of 7-24 MHz.

The setting of the output P-loop also starts from the 28 MHz range. To do this, observing the precautions, shift or push the turns of the coil l 4, and also adjust the capacitances of capacitors C7 and C18. After tuning, by applying a full input power of 60-80 W to the input of the amplifier, the "cathode" and then the P-circuit are again adjusted. The maximum anode current can reach 0.45-0.5 A.

It should be noted that without changing the circuit, two GK71 lamps can be installed in the amplifier, respectively increasing the power of the Tr1 transformer and the dimensions of the device itself.

Section: [High frequency power amplifiers]
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The power amplifier (PA) is made on the "old" reliable GK71 lamp, with a graphite anode that does not require airflow. The schematic diagram is shown in fig. one.

Power delivered to a load equivalent of 50 ohms Pout = 500-700 W.

The features of this UM scheme are:

the introduction of a protection circuit against overcurrent and short circuit (short circuit) and the maintenance of "Sleep mode" in the MIND;
the use of a cathode resonant circuit for better matching with imported transceivers;
the original P-loop circuit, which allows you to get the same output power on all ranges.

Rice. 1. Schematic diagram of the GK71 power amplifier with a common grid.

The PA is powered by one powerful transformer made on a torus. A high anode voltage of 2.5-3.0 kV is obtained by doubling the voltage taken from the step-up winding of the transformer.

When the PA is turned on, the mains voltage of 220 V, passing through the mains filter Lf, C42, C43, SA4 circuit breaker, is fed to the primary winding of the transformer through the HL1 halogen lamp. This provides a “soft” start and extends the life of the VL1 GK71 lamp and other PA elements.

The SWR at the PA input does not exceed 1.5 on all bands and is in good agreement with any imported transceiver, even without a tuner.

Switch SA1.2 shorts the 3.5MHz coil. Switch SA1.1 switches range relays. If a 1.8 MHz band is planned, then you need to add another relay and use the 9th position on the SA1 switch.

correct operation of the UM;
no burning of relay contacts K1, K2.

Power amplifier design

The UM is made in the body of the computer system unit, preferably the old model of the 80s - it is made of thicker steel. Dimensions 175x325x400 mm. The vertical partition and horizontal shelves are made of steel 1.5-2 mm thick.

With intensive work of the PA, it is desirable to use a fan operating at a reduced supply voltage to reduce noise.

Parts and possible replacements

The L3 coil of the 10-21 MHz range is made of a copper tube with a diameter of 5-6 mm and contains 15-17 turns, the outer diameter is 50-55 mm.

The L4 coil of the 28 MHz range is made of copper wire with a diameter of 2.0-2.5 mm and contains 5-6 turns, the outer diameter of the coil is 25 mm.

Dr3 - winding station wagon with PELSHO wire 0.2-0.3 mm 2-4 sections of 80-100 turns.

The mains filter Lf is wound on a K45x27x15 mm 2000NN ring in two wires with a diameter of 1 mm, with good insulation of the MGTF type, turn to turn until filled.

Transistors VT1 - KT835, KT837. VT2, VT3 - KT829A. DA1 - KR142EN-9 (B, D) or MC7824.

Kilowatt amplifier on GK-71 output power tube amplifier is determined by the expression Pout = 0.2EAlmax, where EA is the supply voltage of the anode circuit; lmax - maximum cathode current. For GK-71 lamps, 1max \u003d 0.9 A. Let's take two lamps connected in parallel, then to obtain an output of 1000 W, anode voltage Ea \u003d 1000 / (0.2 * 2-0.9) \u003d 2777 V is required.

From the GK-71 reference data it follows that the maximum allowable Ea = 1500 V. But for this lamp, an anode-screen modulation mode is provided, when the anode voltage increases by 2 times, i.e. up to 3000 V. Amateur radio experience shows that the GK- 71 at this anode voltage works quite reliably: for example, the well-known Leningrad radio amateur, repeated champion of the USSR in short-wave communications, Georgy Rumyantsev successfully used the GK-71 at an anode voltage of up to 5000 V.

Many radio amateurs also have doubts about the possibility of using the GK-71 on the 10 m band and even on the 15 m band, since the same reference data indicate: the maximum permissible operating frequency is 20 MHz. But this figure, obviously, migrated to the reference data from the TOR for the development of the GK-71. But the GK-71 itself knows nothing about this and works fine even at a frequency of 50 MHz. So, in the 50s, an amateur television center in Omsk worked on the first television channel (48.5 ... 56.6 MHz), having exactly two GK-71 lamps in the output stage.

Specifications kilowatt amplifier on GK-71

Operating ranges, m 10-80, 160 (optional);

Input SWR (on all ranges), no more than 1.5

Output power (on all ranges), W, not less than 1000

According to correspondents, out-of-band radiation was not detected.

The kilowatt amplifier circuit on the GK-71 is shown in the figure. The output power of the transmitter in the range of 160 meters cannot exceed 10 W, but taking into account that someday even more power may be allowed for it, the input contour of this range is shown by a dashed line.

The input signal from connector XW1 is fed to contacts K1.1 of relay K1. When the amplifier is off (power is not applied to all its relays), the input signal through the contacts K8.1 of the relay K8 goes to the output of the amplifier - connector XW3.

Relays K1 and K8 are controlled by contacts K2.2 of relay K2. +12 V is constantly supplied to one output of its winding when the amplifier is on, and the other output through the XW2 ”PTT” connector is closed to the case when the transceiver switches to transmission. As a result, relay K2, and with it relays K1 and K8, are triggered. The transition to gear is indicated by the signal lamp NI.

In the "Transmission" mode, the input signal from the contacts K1.1 of the relay K1 goes to the input range P-circuits (160 m - C1L1C2 80 m - C3L2C4, ... 10-12 m - C11L7), to which the input capacitance of the lamps VL1 and VL2 is also added . The broadband of these circuits made it possible to combine the ranges of 17 and 20 m. The excitation signal is fed to the filaments (cathodes) of the lamps VL1 and VL2 through the capacitors C12 and C13, and the lamps operate according to the circuit with grounded grids, and the supply voltage is not applied to these grids. With this switching on, the quiescent current of two GK-71 lamps (anode voltage 3000 V) is mA and there are no step-type distortions. Resistors R1 and R2 prevent the amplifier from self-exciting. Through the contacts K2.1 of the relay K2 in the receive mode, the control grids VL1 and VL2 are supplied with a voltage of +12 V, which is enough to completely turn off the lamps in this mode.

A P-circuit is included in the anode circuit of VL1 and VL2 (according to the “parallel power” scheme), which ensures the matching of the amplifier with almost any antenna. Its switching on different ranges is carried out by the contacts of the KZ-K7 relay. The windings of the coils of the circuit on the ranges of 15 and 17 m, as well as 30 and 40 m are pairwise single, and on the range of 160 m all contacts are open and the maximum inductance is set.

Resistor R3 protects the anode lamp power supply from failure in the event of an accidental breakdown in one of the lamps (in this case, it burns out instantly and must be replaced). The RA2 voltmeter with a trim, which indicates the value of the output signal, is connected in parallel with the XW3 connector, so the indication is also carried out when the amplifier is turned off (the “autonomous” operation of the transceiver for transmission).

All supply voltages of the kilowatt amplifier on the GK-71 are provided by a power transformer that has only two secondary windings: winding II feeds the voltage doubler (R4-R13, VD1 -VD10) with an output voltage of 3000 V, and winding III with a bipolar 12 V rectifier provides lamp incandescence VL1 and VL2. The voltage between terminals 5 and 7 of this winding is 24 V, and after the L10 inductor, 22 V remains on the filaments, so VL1 and VL2 work with an allowable cathode overheating, which provides a sufficient quiescent current of the lamps at an anode voltage of 3000 V.

Power transformer T1 was manufactured by a specialized enterprise according to the following assignment: winding I - network 220V 50 Hz; winding II - 1100V, current 1.5A; winding with terminals III - 2 × 12 V, current 7A. The transformer is wound on a toroidal magnetic core made of HVP steel.

All rectifier diodes VD1 - VD10 and VD12, VD13 for a current of 5 A and reverse voltage 2000V (of course, VD11 and VD14 can be for a lower reverse voltage). Relay K1 - RPV-2/7 for a voltage of 24 V. Relay K2 - RES-9 for a voltage of 12 V, relay KZ-K7 - vacuum circuit breakers of the V1V-1T1 type. As K8, the TKE54PD1 contactor is used, all four groups of contacts of which are connected in parallel, which guarantees a minimum of signal losses in the receive mode.

The data of the inductors are given in the table

(for coils L8 and L9, the number of turns is indicated, counting from the left output according to the diagram in the figure). The L10 inductor is wound on a toroidal magnetic core made of 1000NM ferrite, 50 mm in diameter (outer) and 30 mm (inner), 10 mm thick. The windings are made with four MGTF-0.75 wires (each winding has 2 wires in parallel) and has 30 turns. The wires are neatly arranged on the core and occupy almost the entire surface of the core.

Choke L11 is wound on a porcelain frame with a diameter of 28 mm, wire PShK-0.44. The total length of the frame is 120 mm. Starting from the “hot” end of the inductor, 12 turns are evenly distributed over a length of 40 mm, and the rest of the inductor is wound with the same wire, turn by turn, over a length of 70 mm. To fix the turns, it is advisable to coat the winding with BF-6 glue, and then dry it. The described choke works “perfectly” on all amateur HF bands and can be recommended for other power amplifiers.

Capacitor C19 must have a gap between the plates of at least 2.5 mm, and C22 - at least 0.7 mm.

The kilowatt amplifier on the GK-71 is assembled in a housing from a measuring device with thick (cast) side walls. Housing dimensions (WxHxD) - 460x200x430 mm. The bottom cover of the case is made of duralumin 3 mm thick, and most of the amplifier parts are attached to it. The figure shows a view of the kilowatt amplifier on the GK-71 from above with the top cover removed. The author strongly recommends that the arrangement of parts shown in the figure be followed, as it is the fruit of extensive experience in the manufacture of power amplifiers.

GK-71 lamp panels are installed on a U-shaped compartment, the height of which is equal to the height of the body. Under it, in the bottom, there is a rectangular hole equal to the entire area of the compartment, the same hole is in the top cover of the case. The latter is covered with a plate mounted on posts 30 mm high. Since the case is mounted on a table with high legs (see Fig. 2), air passes freely past the lamps, which ensures the normal temperature conditions of the amplifier. Capacitors C21 and C23 are placed one above the other. Almost all the small parts of the amplifier are installed on three boards, and the board with the rectifier parts is installed above the T1 transformer.

Yakov LAPOVOK (UA1FA), St. Petersburg

Decide on the use of good old glass lamps in the power amplifier (PA), then you will forget about blowing, warming up, training and so on.

500W output power is better than 100W! UM is designed to work on amateur bands 10, 12, 15, 17, 20, 30.40, 80 m and 160 m. Peak output power in the absence of distortion of the amplified signal - 500 watts.

It is made on a VL1 type GK71 lamp, switched on according to classical pattern with a common cathode. The input impedance of the amplifier and the stability of its operation on all ranges are provided by the resistor R1, which allows the imported transceiver (and the amplifier is designed for it) to operate at a constant load of 50 ohms with a minimum SWR.

Rice. 1. View of the front panel of the power amplifier (PA).

With a transceiver output power of 5 watts, the amplifier delivers 500 watts of peak power. The required small input power of the PA allows it to be used with imported and home-made transceivers with a maximum output power of up to 10 W, which have an output power adjustment.

The anode circuit of the VL1 lamp is made according to the serial power supply scheme. Which also has a beneficial effect on increasing the coefficient of performance (COP) of the amplifier in the HF bands.

If today many shortwaves have the opportunity to use branded transceivers, then power amplifiers, as a rule, are forced to manufacture their own. This section proposes a complete design of a modern PA for an amateur HF radio station.

The common cathode (CC) circuit has a high input impedance across the first grid. The input signal source is required to provide only a small reactive current through the input capacitance of the lamp, and there is no active component of the grid current, moreover, its appearance is harmful, therefore, a small input power is sufficient for the PA to work with OK. In a real circuit, the power gain of a circuit with OK can reach several tens of decibels.

It should be noted that the PA according to the circuit with OK is sensitive to overload by the input signal. In addition, due to intermodulation distortion, the radiated frequency band of the SSB signal is greatly expanded.

It is important to comply with the passport data of the lamp modes, it is necessary to accurately withstand the filament voltage. An underestimated filament voltage has a much worse effect on the durability of the lamps than an overestimated one.

By operating an expensive imported transceiver at low power, using a tube PA, we unload the transistor output stage of the transceiver, as well as the power supply to the transceiver.

circuit diagram

The power amplifier, the schematic diagram of which is shown in fig. 2 provides the necessary gain on all nine amateur HF bands. It is made on a VL1 lamp connected according to the common cathode circuit.

In the absence of a control signal at the XS1 connector (the control pedal is not pressed) or the amplifier is turned off, the input signal from the antenna connected to the XW2 RF connector passes through the circuit through the normally closed contacts of the K2 and K1 relays to the XW1 “Input” connector and then to the transceiver.

When switching to transmission mode, the XS1 socket receives a control signal from the transceiver. Through the circuit through the SA3 switch, the short circuit relay winding is supplied with a voltage of +24 V to an open-collector transistor switch in the transceiver. When the transistor key of the transceiver is opened, the short circuit, K1, K2 relays are activated.

Rice. 2. Schematic diagram of the power amplifier (PA).

Trimmer capacitor C4 serves as a tuning of the range circuits. In the receive mode, the relay contacts K3.1 are open. Relays K1 and K2 are de-energized.

Contacts K1.2 are open, a voltage of minus 150 V is supplied to the control grid of the lamp, while the lamp is closed.

It is necessary to choose an offset such that it reliably closes the lamp in the receive mode. A poorly sealed lamp can make noise and interfere with reception.

The contacts of relay K1 K1.2 switch the bias circuit, and a stabilized voltage of minus 80 V is supplied to the control grid in the transmission mode. Relay K2 with its contacts K2.1 connects the antenna to the PA output.

The load is a P-loop, which ensures the matching of the amplifier with antennas having different input impedance. The usual P-circuit C13, L8 and L9, C17 is included in the anode circuit of the lamp.

To prevent self-excitation of the amplifier, a low-resistance resistor R2 is included in the control grid VL1. The anode circuit of the VL1 lamp also includes an element of protection against self-excitation on VHF - a choke Dr3 with a small inductance shunted by a resistor R4 that cuts off its action at operating frequencies. Self-excitation is possible, despite the mythical "low frequency" of GK71.

Inductor Dr2 is connected to the P-loop at the point with the least resistance and RF voltage. Therefore, it does not affect the operation of the amplifier on high frequency. Structurally, it can be placed close to the walls of the amplifier housing, which simplifies the layout.

At high frequency, the inductor is connected in parallel with the load, its shunt action is low and it can have a lower inductance. The required inductance, even with a margin for connecting a high-resistance antenna, is 20-30 μH. Accordingly, the own capacitance and dimensions of the inductor are reduced.

At the output of the P-loop, an indicator of the output signal level (HF voltmeter), elements C18 * is connected. VD5, R6, R7, C19, C20 and PA1, facilitating the setting of the P-loop and correct matching with the antenna. The required sensitivity of the indicator is set depending on the actual input impedance of the antenna by adjusting the resistor R6.

The UM has a bypass mode. SA3 is used to enable it. The lamp operates with maximum linearity in the absence of grid current.

To control the control grid current, it is desirable to turn on a small pointer microammeter. It is useful in measurements and tests. During operation, it can be safely replaced with a low-power VD3 LED, in parallel with which a simple VD4 diode must be connected, through which a bias voltage will be applied to the grid.

The lamp filament is powered by AC voltage 21-22 V. This provides the correct emission current for linear operation of the amplifier while maintaining long lamp life.

Design

The PA is assembled on the basis of the legendary transmitter unit from the RSB-5 radio station. This is an aluminum case with a 115 mm chassis basement. Ideal for this design.

The socket of the GK71 lamp is fixed at a height of 55 mm. The housing measures 200x260x260 mm (WxHxD) without protruding elements.

The upper compartment contains the details of the output P-circuit C12, 04, C15, C16, C17, Dr2, L8, L9 - a turntable, relay K2.

The front panel has:

knob and turntable scale;
pointer meter RA1;
variable resistor R6;
antenna connectors XW2 and XI;
capacitor handles C4.03, 07;
switches SA1, SA2;
switch SA3.

Variable capacitors are equipped with scales, which is very convenient for tuning.

In the lower compartment, C4, 03, coils LI, L1 "- L7, L7 ’, a switch of ranges SA1, relays K1 and short circuit are mounted. Connectors XW1, XS1, XP1, X2 are installed on the rear wall of the lower compartment.

The upper U-shaped cover covering the UM unit has oblong holes on the sides and a raised top cover by 10 mm. There are holes in the cover covering the bottom of the unit to improve the cooling of the amplifier. All this is done to reduce the ingress of dust into the PA.

Parts and possible replacements

At the input of the amplifier, bandpass filters with inductive coupling are installed, providing:

firstly, galvanic isolation from the transceiver;
secondly, good range filtering.

The input grid circuits are switched by the SA1 switch. Data input inductors are given in table. one.

Range	Number of turns, L	winding	Sdop	Wire diameter, mm	Frame diameter, mm	Communication coil, L1	Wire diameter, mm



		winding length 30mm
					16 hex.
					16 hex.
					16 hex.

Table 1. Input inductor data.

Grid choke Dr1 is wound on a sectioned porcelain frame. Outer diameter - 20 mm, total length - 39 mm. It has 4 sections with a width of 4 mm, the diameter in the section is 11 mm with partitions 2 mm thick.

Wire brand PELSHO 0.1, winding up to filling.

A P-loop is used at the output of the power amplifier. The L8 output P-loop coil is frameless wound on a mandrel with a diameter of 40 mm and contains 5 turns of a silver-plated copper tube with a diameter of 5 mm, the winding length is 30 mm. The high quality factor of this coil ensures full power output on the 10m band.

As an inductor L9, a “turntable” and a counter of turns from the RSB-5 radio station or the like, for example, from the Mikron radio station, were used.

P-loop inductors are wound in one direction. During the tuning process, a “turntable” from the R-111 radio station, with an inductance of 1.3 μH, was used as L8. These coils have one drawback - the silver-plated surface oxidizes over time, and the contact may be broken, for which you have to clean it.

For this purpose, it is best to use ammonia. Capacitor 03 of the P-loop setting must have a gap between the plates of at least 1.2 mm. A capacitor from the RSB-5 (R-805) radio station is well suited; the gap between the plates is 2 mm.

Capacitor C17 regulates communication with the antenna, the gap is at least 0.5 mm. Capacitor C17 is used from old-style radios, this is a three-section version with a gap of 0.3 mm if the antenna has an input impedance of 50-100 ohms.

If you plan to use antennas with higher input impedance (such as long wire, VS1AA or "American"), the gap between the C17 plates must be at least 1 mm to avoid unwanted electrical breakdowns of the air gap.

The Dr2 inductor is wound on a ceramic frame with a diameter of 13 mm and a length of 190 mm. Its winding is made with PELSHO 0.25 wire, the number of turns is 160. Up to half of the frame - winding turn to turn, then in sections with 5 mm intervals, and from the hot end part of the turns of the inductor has a progressive winding.

Inductor Dr3 contains four turns of wire, evenly distributed along the length of the body of the resistor R4 type MLT-2.

Connectors: XW1, XW2 - RF connectors SR-50-165f; XS1 - SG-5; X1 - clip-on HF insulator, X2 - clip-on ground. XP1 connector type RP 14-30LO or RP-30.

SA1 - biscuit ceramic switch type PGK 11P 1N two boards. SA2 high-frequency ceramic switch from PCB-5.

Fixed resistors types MT-2, MLT, S1-4, S2-23, R6 - variable resistor type SPO, CH2-2-1. Trimmer resistor R7 SPZ-19, SPZ-38.

Capacitors of type KD, KM, KT, K10-7V, KSO. Trimmer capacitor C4 type KPV, KPVM. Capacitor C14 type K15U-1 150 pF 7 kvar 6 kV.

Capacitor 08 - constructive, is a piece coaxial cable located near the inductor L9.

SA3 toggle switch type PV2-1, TP1-2, MT1, PT8 or P2K.

The operating voltage of all relays is 24-27 V. The contacts of the high-frequency relays K1 and K2 must withstand a passing power of 100 and 500 W, respectively. Relay K1 - RPV 2/7 with an operating voltage of 27 ± 3 V, winding resistance 1100 Ohm, actuation current 13 mA, release current 2 mA.

Relay winding polarity:

output A - minus;
conclusion B is a plus.

Passport RS4.521.952 or RS4.521.955, RS4.521.956, RS4.521.957, RS4.521.958.

You can apply RES-59, passport HP4.500.025. Well suited RES-48 passport RS4.520213. Relay K2 HF type "Hook" or similar for an operating voltage of 24-27 V.

If it is not planned to use antennas of the type Long Wire, VS1AA and the like, then a relay of the TKE54PD1 type is well suited as a K2 relay.

Short-circuit relay type RES15 passport RS4.591.001, RS4.591.007, KhP4.591.014 can be replaced by RES-49, passport RS4.569.421-00, RS4.569.421-04, RS4.569.421-07. All relays are connected by twisted pair.

Measuring device PA1 with a total deviation current of 1 mA type M4231.

Diodes VD1, VD2, VD4, VD6 - KD522 or other silicon, VD3 - AL310, VD5-D2E, D18.

Setting

When setting up a tube PA, all precautions must be observed, since it contains high voltage that is life-threatening. Never turn on the amplifier without the top cover installed.

If used for a long time, the top cover of the amplifier will become very hot, which may cause burns. Do not touch these parts of the PA during operation.

Before removing the top cover, make sure the PSU has been turned off for at least 5 minutes. During this time, the electrolytic capacitors will be completely discharged.

First of all, it is necessary to calibrate measuring instruments by comparing their readings with exemplary ones. It is impossible to select shunts at operating voltages.

Focus on checking the correctness and quality of installation. A PA made without errors usually does not require much adjustment and immediately starts working.

A transceiver is connected to the input of the amplifier. For most imported transceivers, the output power is smoothly regulated. When you first turn on the PA with the transceiver, the power supplied to the PA input must be reduced to a minimum.

The YAESU FT-950 transceiver has a minimum output power of 5W. That's where we started with.

Looking ahead, let's say that during operation, 5 W is quite enough to build up the PA on one or two GK71 lamps. The input non-inductive resistor R1 can be excluded from the circuit. In this case, the SWR with the tuner built into the transceiver turned off on all ranges is 1-1.2, with careful selection of the turns of the communication coil, and with the tuner turned on, the SWR is 1.

With one lamp, the anode current reaches 350 mA. The maximum allowable buildup should not allow the appearance of the control grid current. If you want more power, you should not increase the buildup and prevent the grid current.

In this case, it is better to increase the screen voltage, set the lamp to the same quiescent current, so that the maximum buildup is achieved without the control grid current.

Connect to amplifier output:

or a load equivalent of type 39-4 per 1 kW, having a voltage output of HF 1:100 on the connector, and a V7-15 tube voltmeter;
or an incandescent lamp with a power of 500 W for a voltage of 220 or 127 V (used in railway transport).

SA3 - in the "On" position. We turn on the PSU, measure the quiescent current of the lamp, which should be about 30-40 mA.

We adjust the input range circuits to resonance with capacitor C4. The variable capacitor must not be in the extreme position. If necessary, change the number of turns of coils L1-L7.

The exact selection of the turns of the communication coils L1 "-L7 'is carried out according to the minimum of the KVS-meter built into the transceiver.

In the ranges of 18 and 21 MHz, 24 and 28 MHz, the same circuits L6, L6 'and L7, L7 "work.

The switch SA2 connects the variable anode capacitor C13 on the bands 160-30 m, and on the band 160 m - additional capacitor C14. Capacitor C13 is off on 20-10m bands. In this case, the adjustment is made by the inductor L9 and the coupling capacitor C17.

Finally, connect the antenna with which the PA will work. Do not turn on the PA without an antenna connected. After switching on without an antenna, life-threatening high voltage can be generated at the antenna connector.

There are three controls. On low-frequency ranges, the anode capacitor C13 is set to a large capacitance and inductance. By varying the inductance, we set the output circuit to resonance, and with the capacitor C17 we establish the necessary connection with the load.

To avoid false tuning, the rule to follow is that capacitances C13 and C17 should always be set closer to the maximum value, which will also correspond to maximum harmonic suppression.

By manipulating capacitors C13, C17, inductance L9, the output indicator PA1 is maximum reading on each range. At the same time, keep an eye on the decline in the anode current.

For reliable operation of the PA, good grounding is necessary. To remove static electricity induced in the antenna, it is useful to turn on the throttle from the SW2 connector to the housing.

The data of the anode capacitor is as follows:

range 160 m - 270 pF;
range 80 m - 120 pF;
range 40 m - 70 pF;
range 30 m - 39 pF;
on other ranges - the anode capacitor is disabled.

During operation, for a quick transition from range to range, it is necessary to compile a table of the positions of the capacitor rotors corresponding to them and the readings of the turntable counter.

the method of calculating the P-loop is familiar to readers of this book, It is described in the reference literature. There are ready tables for different Roe. There are many virtual calculators on the Internet for such calculations.

Calculations say that at 28 MHz you need a circuit with an inductance of 0.5 μH and a capacitance of the "hot end" of the P-loop - 40 pF. And we have 2 GK71 Cout \u003d 17x2 plus C installation \u003d 45-50 pF. Here we can conclude that 2xGK71 will not work at 28 MHz.

The way out of the situation is to use the serial power supply of the P-circuit, and use the Dr2 inductor with a lower inductance, which is now not included in the mounting capacity. We generally exclude the anode variable capacitor from the circuit.

Lamp training

I had to experiment a lot with GK71, they do not need training. But it is advisable to train random and long-life lamps in this sequence.

Rinse dirty lamps in water with washing powder, rinse thoroughly so that the water rinses the inside of the base and dry. Spare lamps, which also did not work for a long time, are useful to train. In the future, they will be ready for work immediately and guaranteed.

Hold the lamp under incandescence for several hours, then apply bias voltage. Next, apply a reduced anode and screen voltage, reduce the grid bias until a small anode current appears, and again withstand several hours.

We reduce the bias voltage until the anode current is obtained, so that the anodes turn slightly pink, let them bake for a while.

From working lamps, from time to time it is necessary to remove dust from the top of the cylinder with a dry, clean rag (with the PA turned off and the capacitors discharged).

Feeding the filament of a powerful generator lamp

Properly chosen filament voltage of a powerful generator lamp will allow the lamp to serve several times longer, increase the reliability of its operation and facilitate its temperature regime. It is done like this.

We turn on the LATR in the primary winding of the filament transformer, set the nameplate filament voltage. We tune the PA to maximum power with a single-frequency signal. At full power, slowly reduce the voltage supplied from the LATR until the output power begins to decline.

We add the filament voltage by 10% (this is the emission margin). We measure the voltage on the primary winding of the filament transformer. In series, we select a quenching resistor in the primary winding of the transformer to obtain the measured voltage, at the rated mains voltage.

Mounting UM

The input range circuits are located in the basement of the chassis. Details of the anode load of the lamp - above the chassis. The conductors of the RF circuits are as short as possible and preferably straight from a single-core silver-plated copper wire.

The layout of the PA is visible in the photograph (Fig. 3). Photo of the internal layout of the amplifier from the rear panel.

A variant with two GK71 lamps is shown in fig. four.

Rice. 3. View of the power amplifier (PA) on the right.

Rice. 4. View of the power amplifier (PA) from behind.

Power supply: features

Each source must deliver the required voltage and current at the maximum load of the amplifier operation. It is necessary to check them when the mains supply voltage changes in the line.

The mains voltage changes during the day. It usually falls in the evening and peaks in the middle of the night. Depends on the season, the remoteness of the home from the transformer substation and the state of the electrical network.

In the power supply unit (PSU) to the PA, the primary (network) winding has taps and with large fluctuations in the mains voltage, especially in rural areas, it is possible to adjust the voltage.

It should be taken very seriously to stabilize the voltage on the screen grid of the lamp.

For this you can use:

a separate winding on the anode transformer or a separate small transformer;
powerful semiconductor zener diodes of the type D817, D816 on radiators.

For the anode power supply of the lamp, an unstabilized voltage is usually used. But the larger the capacitance of the filter capacitors, the less distortion will be during SSB operation and the clearer the signal will be during CW and DIGI operation.

It must be remembered that, no matter how good and linear the lamps used are, the foundation for the high-quality operation of the PA is its power supply. The authors advise not to save on the power of the anode transformer and on the capacitances of the anode voltage filter.

The design of the PA separately from the PSU makes it easy to upgrade any node of the unit without affecting the other. The PSU is located under the table, the compact UM is in a convenient place. The PSU is made according to a simplified scheme without automatic switching on and off.

It is possible to step change the anode voltage, which is performed by switching the network winding (switch when the PSU is disconnected from the network!). The anode rectifier is built on a bridge circuit with a filter capacitor consisting of series-connected electrolytic capacitors.

Power supply: circuit diagram

The power supply circuit is shown in fig. 5. The power supply of the amplifier consists of two transformers T1, T2 and the corresponding rectifiers. Fuses FU1 and FU2 are included in the network windings.

Rice. 5. Schematic diagram of the power supply unit (PSU) for the power amplifier on GK71 lamps.

From transformer T1 we get:

filament voltage ~ 20 V at a current of 3 A (6 A) with a midpoint;
voltage +24 V used to power the relay windings;
voltage +30 V to power the third grid of the lamp.

There is a separate winding ~ 6.3 V. A transformer is used from a lamp black-and-white TV TS180 with rewound secondary windings. The network winding can be switched on for 220 V, 237 V and 254 V.

Transformer T2 with a power of 1000 W, in which the secondary windings are wound. Outputs from the mains winding are provided for switching to another voltage. These outputs can be used in field (rural) conditions with under or over voltage of the mains.

From the secondary windings we get:

blocking voltage -150 V;
stabilized bias voltage bias voltage -80 V;
stabilized screen voltage +450 V.

If necessary, there is a voltage of +500 V and +1800 V.

The diode bridge VD5-VD12 is used to obtain a voltage of +500 V. The filter consists of an inductor Dr1 and capacitors C2, C3. Zener diodes VD13-VD15 and resistor R4 are used to obtain a stabilized voltage of +450 V.

The diode bridge VD16-VD19 is loaded on the electrolytic capacitor C4 and then the zener diodes VD20-VD22 are turned on, we get -150 V and during transmission - a stabilized voltage of -80 V.

Diode bridge VD23-VD26 and smoothing capacitors C6-C11 are used to obtain high voltage. Each PSU electrolytic capacitor is shunted with a 68-100 kΩ MLT-2 resistor to equalize the voltage and discharge them after the PSU is turned off.

The device RA1 serves to control the anode current. The PA1 device has a current measurement limit of 1 A.

Through the XP1 connector, the necessary voltages are supplied from the PSU to the PA via a multi-core cable. For filament circuits, the cable cores are soldered in parallel. To increase the insulation, a PVC cambric of the appropriate diameter is additionally put on top of the main insulation on the high-voltage wire.

A more preferred option, which is used in many amateur radio developments, is to supply anode voltage from an external power supply unit to the SR50 high-frequency connector via a piece of RK-50 or RK-75 coaxial cable with a diameter of 7-12 mm. At the same time, in order to increase safety, the screen braid of the cable is connected to the PA and PSU cases.

When the PSU is turned on with the SA1 toggle switch, the filament voltage and the voltage to power the relay are supplied. Toggle switch SA2 turns on the blocking voltage, the screen grid and the anode voltage. When switching off, the voltage is relieved in the reverse order.

Control lights HL1, HL2 are used to control the inclusion of transformers T1, T2, respectively.

The PSU is assembled in a separate case. It has dimensions of 390x230x230 mm, chassis basement 50 mm, weight about 20 kg. On the front panel of the PSU case there are network switches SA1, SA2, fuse holders FU1, FU2, bulbs HL1, HL2, device PA1, and on the rear wall there is an XP1 connector and an X1 clamp terminal. The inscriptions on the front panel are made using a transfer font.

Power supply: parts and analogues

Connectors: X1 - terminal-clamp; XP1 - 30-pin connector type RP14-30L0 or RPZ-ZO. Trimmer resistors R1-R2 of the PEVR type with a power of 5-15 W, R13 - a shunt to the specific RA1 device used.

Electrolytic capacitors C1 - 150 uF x 70 V, C2, C3 - K50-7 with a capacity of 50 + 250 uF x 450/495 V, C4 - 100 uF x 295 V.

The use of modern or imported capacitors for a large capacity and voltage will only benefit, increase reliability.

Capacitors C2, C4, C6-SP are installed through an insulating washer made of foil fiberglass. The foil serves as a negative contact electrolytic capacitor. Capacitors C5, C12 type KD, KM, KT.

Switches SA1, SA2 - toggle switches TV 1-2 250 W / 220 V or B4 250 W / 220 V.

Diodes VD1-VD4 KD202V, VD5-VD12 and VD16-VD19 2D202K or assembled from similar diodes or diode assemblies for the appropriate voltage and current.

Remember about equalizing resistors and capacitors with a capacity of 10000-47000 pf - protection against possible breakdown by short-term pulses, they are not shown in the diagram.

VD23-VD26 - type KTs201D, VD13-VD15 - KS650, VD20 - D817D, VD21 - D817V, VD22 - D817B zener diodes or a set of other zener diodes with the appropriate stabilization voltage, mounted on radiators and isolated from the case.

Measuring device PA1 with a total deviation current of 1 mA, type M4200, M2003, M4202. The power transformer T2 is made of an industrial one, having a primary winding of 220/380 V. In addition, without disassembling the transformer windings, an additional conclusion was made from primary winding between 220 V and 380 V.

Thus, it turned out the possibility of discrete voltage regulation. All transformers must be impregnated with high quality varnish so that air humidity and dew, especially in the field, do not cause breakdown of the windings.

In the BI version for field conditions, the basement of the chassis was made of thick plexiglass. Holes were made in plexiglass, and appropriate threads were cut for attaching electrolytic capacitors.

Operating experience

Several UMs were made according to the described scheme. There were options with one lamp and with two GK71 lamps operating in parallel. They are in use to this day.

To keep the PA in constant readiness and operate at maximum power, set the P-loop to maximum power. If you want to conduct radio communication with neighbor friends, turn down the buildup from the transceiver and communicate at low power.

The power to the maximum in the PA is increased quickly by simply entering the transceiver menu and adding the drive power from the transceiver. The maximum power is used when you need to work quickly with DX, in competition or in poor passing conditions.

In this UM, instead of GK71 lamps, GU13, GU72 and others can be used. This PA is easily consistent with both a low-resistance load of 50 ohms and a high-resistance load when the antennas are powered by a single-wire line.