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Demonstrates the construction of **magnetic loop antennas**, detailing both multi-turn and single-turn designs. It covers a 30-inch diameter multi-turn loop for 80 meters, based on a February 1996 QST article, and an octagon single-turn loop made from 15mm copper tube with a 4.8-meter circumference, operating from 7 MHz to 14 MHz. The document also presents a smaller 800mm diameter loop for 14 MHz to 28 MHz, emphasizing the importance of high-voltage tuning capacitors. Covers the design and construction of custom **butterfly capacitors** and piston capacitors, including a split stator capacitor with 140 pF capacitance and a 6000 Volt rating, and a butterfly capacitor with 5-65 pF and 7200 Volt rating. It explains why butterfly capacitors are preferred over split stator types for high power applications due to lower losses and direct series connection of rotors, reducing resistive losses from wiper contacts. Material recommendations include clear PVC for plates and brass or stainless steel for non-magnetic hardware. Addresses practical considerations such as feeding the loop with a shielded 1/5 Faraday loop made from RG213 or RG8 coax, achieving VSWR 1.1 across bands, and optimizing its placement 180° from the capacitor. It also discusses mechanical joint resistance, dissimilar metal oxidation prevention using Vaseline, and a simple method for determining radiation angle with a TL-light tube. The guide includes diagrams for rotor, stator, and end plate construction.

A 144 MHz kilowatt amplifier project details the construction and performance of a high-power VHF linear using the GU74b tetrode. This Russian tube, equivalent to the Svetlana 4CX800, is noted for its conservative datasheet ratings, performing closer to 800-1000W anode dissipation in practical applications. The design prioritizes compactness and achieves 1.2 kW output with only 20W of drive power, demonstrating a 70% efficiency at 2.5 kV plate voltage. The amplifier has been successfully deployed in demanding _EME_ (Earth-Moon-Earth) operations since June 1994. Challenges encountered during development included achieving stability with a grid-1 input configuration. The author, _CT1DMK_, opted not to publish the full design due to its complexity, suggesting it might be difficult for less experienced builders to replicate successfully. However, he invites direct contact for those with specific interest in the design. Future plans include a "144MHz GS35b compact amplifier" project, promising another kilowatt-plus design. This resource offers insights into high-power VHF amplifier construction and the practical application of specific power tubes.

Gi7b is tube designed for microwaves but working good as HF amplifier. Idea is to build cheap, reliable HF amplifier covering 160 meters band.

PC power supply conversion for ham radio use. Slide show overview showing how convert PC Power supplies to ham radio use presented at the August 2007 FSARC meeting.

The Discovery series of amplifiers are designed and built in the UK by Linear Amp UK Ltd, one of the world's leading amplifier manufacturers, specializing in high power RF tube amplifiers. The amplifiers use large GS31 or GS35 ceramic triode tubes. Band coverage 6m, 2m and 70 cms

A one-tube battery-powered regenerative receiver.

Circuits, pictures and data about toroids, tubes and home made power amplifiers

A great source for hard to find HI END & power tubes & sockets, various capacitors, vacuum relays, various keys and paddles.

HD Communications Corp specializes in **RF and microwave amplifiers** engineered for demanding communication, defense, and industrial applications. Their product line includes precision-built, high-power solutions, along with RF connectors, filters, HF cables, and various accessories. The company also supplies tower hardware, valves, and tubes, catering to a broad spectrum of radio frequency infrastructure needs. Beyond amplifiers, HD Communications offers a range of **RF filters**, including low-pass filters, antenna filters, and solutions for RFI/TVI mitigation. Their inventory encompasses essential components like coaxial cable and various connector types, supporting both amateur radio and professional installations. The company operates as a manufacturer and vendor, providing direct sales of its specialized RF products.

BIRD RF power measuring, new and used, HENRY RF power amplifiers (used HF amps), TOHTSU coaxial relays, SAMLEX power supplies, RFI chokes reduce interference, Parts parts, tubes, Used amplifiers, radios, antennas and accessories, Los Angeles, CA.

VHF UHF Amateur radio antenna and antenna parts, accessories for homebrewers, antenna kits, tubes, antenna masts, antenna tripores, insulators, power amplifier mosfet, power splitters by I0JXX

Building a PEP Power circuit for all analogue watt-meter

Ameritron Al-811H Tuning for Power/Dissipation/Linearity, and More Generally 811A Tube Amps in Grounded Grid

An RF power Amplifier for HF bands with 3 GI-7B tubes by CT1FMS

The Collins TRC-75 autotune linear amplifier, owned by JF2SVU, is presented with a focus on its internal modifications. This QRO amplifier utilizes three 4CX250 tubes in parallel for its final stage, delivering 1 KW output power. Notably, the amplifier achieves full power with only 100 mW of RF input, a characteristic often associated with Collins designs. The original 400 Hz power supply has been converted for easier shack integration, and the entire RF and power supply sections have been rehoused into a compact, clean enclosure. The control unit, positioned above the amplifier, features three meters for individual vacuum tube IP monitoring and a multi-meter on the right. A dedicated 7 MHz receiver, recently completed, is also part of this integrated system. The autotune functionality means the main amplifier unit only requires connections for power, control, and coaxial cables, simplifying its operation. Key components like the 4CX250 tubes and NF capacitors are visible, along with the gearing mechanism for the final tank circuit. A timer and relay system manages high-voltage delay and cooling fan off-delay, although the cooling fan's airflow is noted as somewhat insufficient. A central volume control, which experienced a contact issue, is also highlighted.

How the tube converts DC to RF Power

Svetlana tubes also Russian capacitors,vacuum and coaxial relay, for RF Power Linear Amplifier builders. Amateur-Radio, Broadcast. Full Online Catalog.

This article loaded with nice pictures and schematics, describes a 160-10 meter linear amplifier that uses a pair of 3-500Z triode power tubes. It was designed and constructed by William Moneysmith, W4NFR. The amplifier features fast warm up and 1500-Watt RF output with 100-Watts of drive.

A comeplete home made 600W LDMOS RF power amplifier. Settings can be made on a 7-inch touch screen, and on this screen you can see a lot of useful information during operation, such as output power, temperature, SWR, and so on. The power amplifier includes 2 MRF300 LDMOS FETs and several built-in sensors. The amplifier also contains several types of protection functions like too high current, too high swr, too high temperature, etc.

Article on tubes and their usage in power amplifiers design. Explain failures of tube in RF power amplifiers, a common problem in the SB-220 SB-221, TL-922 and other amplifiers.

ECONCO has been rebuilding vacuum tubes for more than 30 years. Our commitment to quality, and concern for the environment has won us the acclaim of clients worldwide.

1500 watts of RF output on the 70cm band requires robust amplifier design, a challenge addressed by this project featuring the GS-23b / 4CX1600U Svetlana tube. The resource details the construction of a high-power UHF amplifier, providing insights into component selection and layout necessary for stable operation at these frequencies and power levels.

Excellent article and guide to choose the best RF power amplifier that fit your needs by ON4SKY

This video will provide a foundation for understanding how power amplifier circuits work. If you are new to High Frequency Power Amplifier Circuit Design, this is the place to start.

Home Brew a 4-1000A RF power amplifier project by W4NFR

This article describes an alternative to water as the cooling liquid for amateur radio vacuum tube power amplifiers. This cooling system is designed for adequate vacuum tube cooling, reasonable cost, and very low maintenance. By K8CU

How to navigate FlexRadio PowerSDRs Pan Adapter

Common problems of the 572B tubes often used in many RF Power Amplifiers

Maintaining vintage Eddystone receivers often presents unique challenges, as detailed by Victor Jenkins in his refurbishment of an EA12, where his deep understanding of RF circuits ensures optimal performance for daily shortwave listening. Similarly, Gerry O’Hara VE7GUH, a prolific contributor to the EUG website and a trustee, meticulously documented his restoration of an Eddystone S830/2, even addressing an unusual instability issue with a follow-up postscript article and YouTube videos demonstrating the fix. His work, along with numerous other articles on the "Restorations" page, showcases a master's approach to bringing vintage sets back to factory specifications or better. Beyond technical restorations, the EUG also shares compelling historical narratives. One such story recounts the discovery of a long-lost 78rpm recording featuring Eddystone Radio Ltd.'s founder, George Stratton Laughton, and other key figures discussing the company's wartime and post-war contributions to shortwave communications. This six-minute BBC production, transcribed into an MP3 file by Peter Carney, offers a rare auditory glimpse into the company's legacy, highlighting its role in supplying equipment to police, ministries, and expatriate British workers. The community aspect thrives through shared experiences, like Roger Trickett's anecdote about his Eddystone EC10, which has been continuously powered for 50 of its 54 years, traveling across continents and enduring various modifications. Another intriguing account from Roy GM4VKI details the "S640 Identity Crisis," where a seemingly standard S640 receiver turned out to be a masterfully engineered 80/20-meter SSB transceiver built into the original chassis by GI3ZX, showcasing incredible ingenuity from a bygone era of amateur radio.

Traveling Wave Tubes , Conventional Traveling Wave Tubes, Microwave Power Modules manufacturer

Demonstrates MegaPhase's extensive product line of RF and microwave coaxial cable assemblies and components, engineered for demanding applications up to 110 GHz. Key offerings include _Test & Measurement Cables_ with superior phase and amplitude stability, _RF & Microwave Cables_ utilizing _GrooveTube®_ technology for high power systems, and a range of RF components like directional couplers and power dividers. The site details specific cable types such as _Alumibend™_ for space-qualified, ultra-light applications through 90 GHz, and armored cables designed for rigorous environments up to 50 GHz, emphasizing their robust mechanical strength and measurement repeatability. The resource highlights applications across diverse sectors, including space programs like the _Hayabusa_ mission, global security (C5ISR), military airborne systems (MIL-T-81490), telecom, and automated testing. It also provides technical insights through "How To" guides on measuring amplitude/phase stability vs. flexure and proper connector cleaning. The company's commitment to quality is underscored by its rigorous testing protocols and a strong warranty, ensuring reliable operation in critical systems.

Station QRP presents various **circuit diagrams** for constructing low-power AM vacuum tube shortwave transmitters, catering to enthusiasts interested in vintage radio technology. The resource details schematics ranging from simple to more complex designs, enabling hams to build their own QRP AM transmitters for operation on frequencies like 6.925 kHz AM. It emphasizes the use of vacuum tubes, providing a technical foundation for understanding and replicating classic shortwave broadcasting methods. The content is geared towards those who enjoy the hands-on aspect of electronics and the unique characteristics of tube-based RF circuits. Building these transmitters allows operators to experience the nostalgia of early shortwave radio, with the site specifically mentioning a pioneer station on 6.925 kHz AM. The designs facilitate experimentation with low-power AM transmission, offering practical application for homebrew projects. The focus on QRP (low power) operation aligns with a segment of the amateur radio community that values efficiency and minimalist setups, providing a distinct alternative to modern solid-state transceivers.

A 50 MHz stable and small power amplifier, suitable for portable and domestic use. This RF Power amplifier delivers 900W with used pair of tubes primary installed into amplifier.

This project involves constructing a dual-band Moxon antenna, optimized for ham radio enthusiasts, with functionality on both the 10-meter and 6-meter bands. The antenna is designed to operate using a single 50-ohm feedpoint, acting as a mini-beam on 28 MHz (10 meters) and as a 2-element Yagi on 50 MHz (6 meters). Performance-wise, it offers a 4.0 dBd gain on 10 meters and 4.3 dBd on 6 meters, with impressive front-to-back ratios of 30 dB and 11 dB, respectively. Builders like Aleks (S54S) and Marcio (PY2OK) have successfully brought this design to life using the provided specifications. Aleks noted that bending the corners of the structure proved especially useful during assembly. The project comes with a detailed parts list, highlighting the use of aluminum tubes with different diameters and lengths to form essential components like the reflectors and radiators. For those looking to fine-tune the antenna, adjustments can be made by altering the length of certain parts that fit into larger tubes. The feeding system is equipped with a balun to accommodate different power levels, making the design versatile enough to handle outputs of either 300 watts or 1 kilowatt.

his article explores the construction of a PL519 tube amplifier, utilizing Ulrich L. Rohde N1UL's insights. Focusing on a modest 25W continuous output, the design ensures robustness with forced air cooling. The detailed breakdown covers input matching, screen grid voltage generation, bias adjustment, anode power supply, heater power supply, and monitoring circuitry, providing valuable guidance for ham radio enthusiasts.

This document provides a comprehensive guide on purchasing high-frequency (HF) high-power amplifiers, discussing key considerations such as new versus used models, tube versus solid-state technology, and troubleshooting common issues. It emphasizes the importance of understanding power needs for activities like DX chasing and contesting, alongside practical tips for selecting and maintaining amplifiers to ensure reliability and performance in various conditions.

Elektrodump.nl is an online shop from the Netherlands specializing in amateur radio products. It offers a wide range of categories including antenna masts, antennas, tuners, coax connectors, and cables. The site also features broadcast equipment, electron tubes, semiconductors, and various electronic components like capacitors and resistors. Additionally, it provides measuring equipment, power supplies, and transmitters, catering to both hobbyists and professionals in the field of radio electronics.

Tubes are a dying technology. All modern transmitters, even high power ones, do work with transistors and other semiconductors. But many fondly remember their first homebrew transmitter and its hard to forget warm glow of a vacuum tube. The Station QRP website is especially for you to come into touch with tube technology. This site is all about handcrafted QRP AM tube transmitters.

A dual insert microphone design for the Icom IC-7300 transceiver utilizes a **Besson BZ2400 M4 Rocking Armature** insert for frequencies from 500 Hz to 3 kHz, exhibiting a rising response of approximately 11 dB. A generic Electret Condenser insert, powered by the transceiver's microphone line, covers the low-frequency range from 100 Hz to 500 Hz. A Low Pass Filter is incorporated after the Electret insert to prevent frequency overlap, and a pre-set potentiometer (VR1) adjusts the low-frequency response, balancing the output of both inserts. The design emphasizes a "Close Talking" arrangement and addresses audio "colorization" by housing the Besson insert in a thick rubber holder with a foam boot, separate from the circuitry, with the Electret insert also wrapped in a foam boot. Critical importance is placed on using the correct BZ2400 M4 insert with 12 holes in its face plate. The frequency response table for the BZ2400 M4 insert shows 0 dB at 500 Hz, rising to +11 dB at 3000 Hz, while the Electret insert with the Low Pass Filter provides 0 dB at 100 Hz, rolling off to -9 dB at 500 Hz and -50 dB at 3000 Hz. This combination ensures a broad, balanced audio spectrum for SSB operation. The project includes a circuit diagram, a comprehensive parts list detailing components like a 1 Henry iron-cored inductor (L1) and various capacitors, and a board layout within the metal tube. The completed unit provides a tailored audio profile for the IC-7300, enhancing transmit audio quality.

This resource details **cooling modifications** for Ameritron AL82, AL1200, and AL1500 HF amplifiers, specifically addressing heat issues encountered during high-duty-cycle digital mode operation. The author, WD4NGB, observed excessive heat in the tank area and band switch on an AL82, attributing it to insufficient exhaust over the 3-500 tubes and a complete lack of exhaust over the tank area. The modifications aim to prevent common failures such as damaged band switches and deformed insulating materials by increasing airflow and exhaust area. The page describes adding five holes to the chassis for enhanced cooling to the band switch and tank area, alongside enlarging the exhaust area over the inner 3-500 tube and the tank area on the amplifier cover, utilizing expanded metal for safety and RF shielding. The original cover featured 26.25 square inches of exhaust; the modified version significantly increases this to 48.5 square inches over the tubes and introduces an additional 15 square inches over the band switch. These changes are intended to resolve heating problems encountered during heavy, 100% duty cycle use in modes like RTTY or long SSB contests, which typically generate substantial heat. The article also discusses upgrading to a higher output fan, such as the G2E085-AA05-21, and modifying tube sockets for improved airflow and reduced back pressure, citing Tom Rauch (W8JI) of CTR Engineering as a source for parts.

Parks on the Air Canada page provides information about the popular Amateur Radio activity that involves operating portable radios from designated parks and nature reserves worldwide. The page presents the objectives of the program, lists over 400 national/provincial/territorial parks, and offers insights from Tracy McKim, VE3TWM, on low power communications and outdoor ham radio operation. It also includes links to YouTube channels with how-to videos on setting up portable stations, Field Day deployment, and POTA activation. Amateur radio operators interested in combining their love for radio with outdoor adventures will find valuable resources and learning opportunities on this page.