1 500-W Rf Amplifier

The frequency range of this amplifier is 1.8 to 54 MHz. The required RF drive for full output is approximately 30 W. The grid compartment (Rl, R2, RFC4, RFC5) must be shielded from other circuitry, particularly the output circuitry. Capacitors include C1, C2 (0.01 µF silver mica transmitting capacitors), C3 (1500 pF screen grid bypass, internal to the tube socket), C4 (2000 pF, 5 kV, two 858S capacitors in parallel), C5 (vacuum variable, 10 to 300 pF, 10 kV, Jennings UCS-300 for plate tuning), C6 (300 pF, 5 kV, Centralab-type 858S), C7 (vacuum variable, 3000 pF maximum, 3 kV, Jennings UCSL-3000 for loading), C8 (0.0014 µF, 10 kV), C9 (0.005 µF, 15 kV oil capacitor), C10, C11 (500 pF, 20 kV "TV doorknob," Centralab), C12 (0.05 pF, 20 A feedthrough, Sprague), and C13, C14, C15 (1000 pF feedthrough), C16 (0.1 µF, 100 volts DC disc ceramic). The diode used is D1 (silicon diode, 1N4148 or 1N914), with F1 being a 3 A fuse. Connectors include J1 (BNC chassis mount), J2 (chassis mount), J3 (HN chassis mount, used with RG213 for 3 kV feed), and J4 (chassis-mount AC outlet, Amphenol 160-2, AL part no. 713-5202). The lamp is a No. 47, 6.3-volt lamp. Inductors include L1 (3.5 turns of no. 10 silver-plated wire, 1 inch ID, 2 inches long, self-supporting) and L2 (24 roller inductor, Johnson 226-1). The meter movement is M1 (1 mA DC meter movement, filament voltage). Resistors include R1 (50 ohm, 60 watt noninductive resistor, thirty 1500 ohm 2 watt carbon composition resistors in parallel), R2 (1000 ohm, 2 watt carbon composition), R3 (100 ohm, 2 watt carbon composition), R4 (220 K, 2 watt carbon composition), R5 (25 ohm, 25 watt wirewound adjustable), R6 (1000 ohm, 2 watt carbon or wirewound pot), and R7 (10,000 ohm, 2 watt carbon composition). Inductors RFC1 (28 turns no. 18 wire solenoid wound on 0.5 inch OD by 2.5 inch ceramic form, plate choke), RFC2 (plate choke, surplus part, suggested B&W801), RFC3 (74 turns no. 20 wire solenoid wound on 0.75 OD by 3 inch ceramic form), RFC4 (9 15 A RF choke, surplus part, suggested Dale no. IH15, HF no. 18-105), RFC5 (1.0 mH RF choke), and RFC6 (10 H, 1 A RF choke) are included. RT1 is a Surgistor, GC 25-933-S, and S1 is an air flow switch, Rotron 2A-1350. The socket is SK1 (Eimac socket, Sk-810B; chimney SK-806). The transformer is T1 (6.3 volts AC at 10 A secondary, Thordarson 21F12, AL 704-2019), and Z1 is a Zener diode (6.2 volts, 1N473).

This amplifier design operates within a frequency range of 1.8 to 54 MHz, making it suitable for various RF applications. The RF drive requirement of approximately 30 W indicates that this amplifier is capable of delivering significant power output, which is essential for effective signal transmission.

The design emphasizes the importance of shielding the grid compartment from other circuit elements, particularly the output circuitry, to minimize interference and maintain signal integrity. The use of high-quality capacitors is evident, with components such as silver mica and vacuum variable capacitors chosen for their stability and performance under high voltage conditions. The capacitors used in this circuit have voltage ratings up to 10 kV, making them suitable for high-power RF applications.

The inclusion of multiple RF chokes and inductors indicates a focus on filtering and stabilizing the RF signal. The design utilizes solenoid-wound inductors to achieve the necessary inductance values while ensuring efficient performance. Resistors are carefully selected for their power ratings and types, including non-inductive and adjustable components, to allow for precise tuning and stability in the amplifier's operation.

The power supply and circuit protection features are also well-considered, with the use of a fuse and a Zener diode to safeguard against overcurrent and voltage spikes. The air flow switch suggests that thermal management is a priority, ensuring that the amplifier operates within safe temperature limits.

Overall, this amplifier schematic represents a robust design tailored for high-frequency applications, showcasing careful selection of components and thoughtful engineering to achieve reliable performance. The frequency range of this amplifier is 1.8 to 54 MHz. The amount of RF drive required for full output is about 30 W. The grid compartment (Rl, R2, RFC4, RFC5) should be shielded from the other circuitry—especially the output circuitry. C1,2—0.01 silver mica transmitting capacitor C3—1500 pF screen grid bypass (internal to tube socket) ca—2000 pF, 5 kV, two 858S capacitors in parallel, Centralab C5—Vacuum variable, 10 to 300 pF, 10 kV, Jennings UCS-300 (plate tuning) C6—-300 pF.

5 kV, Centra lab-type 858S C7—Vacuum variable, 3000 pF maximum, 3 kV, Jennings UCSL-3000 (loading) C8—0.0014 ftF, 10 kV (EM) C9—0.005 ftF, 15 kV oil capacitor C10,11 —500 pF. 20 kV ""TV doorknob," Centralab C12—0.05 pF, 20 Afeedthrough, Sprague C13,14,15—1000 pF feedthrough C16—0.1 /iF, 100 volts DC disc ceramic D1—Silicon diode, 1N4148 or 1N914 F1—3 A fuse J1—BNC chassis mount J2— chassis mount J3—HN chassis mount, used with RG213 for 3 kV feed J4—Chassis-mount AC outlet, Amphenol 160-2, AL part no.

713-5202 Lamp—No. 47 6.3 volt lamp L1 —3.5 turns no. 10 silver-plated wire, 1 inch ID, 2 inches long, self-supporting L2—24 roller inductor, Johnson 226-1 (EM, CC) M1—1 mA DC meter movement, filament voltage R1 —50 ohm, 60 watt noninductive resistor, thirty 1500 ohm 2 watt carbon composition resistors connected in parallel (see text) R2—1000 ohm, 2 watt carbon composition R3—100 ohm, 2 watt carbon composition R4—220 K, 2 watt carbon composition R5—25 ohm, 25 watt wirewound adjustable R6—1000 ohm, 2 watt carbon or wirewound pot R7—10,000 ohm, 2 watt carbon composition RFC1 —28 turns no. 18 wire solenoid wound on 0.5 inch OD by 2.5 inch ceramic form (plate choke) RFC2—Plate choke, surplus part (suggest B&W801) RFC3—74 turns no.

20 wire solenoid wound on 0.75 OD by 3 inch ceramic form RFC4—9 15 A RF choke, surplus part (suggest Dale no. IH15, HF no. 18-105) RFC5—1.0 mH RF choke RFC6—10 H, 1 A RF choke RT1—Surgistor, GC 25-933-S S1 —Air flow switch, Rotron 2A-1350 SK1 —Eimac socket, Sk-810B; chimney SK-806 (BY) T1 —Transformer, 6.3 volts AC at 10 A second— ary, Thordarson 21F12, AL 704-2019 Z1 —Zener diode, 6.2 volts, 1N473

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