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Presents a crystal-controlled CW transmitter design for the 40-meter band, delivering 5 to 7.5 watts output power. The circuit innovatively employs an _IRF510_ power MOSFET in the final amplifier stage, diverging from conventional bipolar transistors. This design offers high gain, nearly 90% efficiency, and robust resistance to high SWR, allowing 30-second key-down operation into an open circuit without damage. A critical aspect is the precise adjustment of the MOSFET gate bias via a 10K trimmer pot, _R10_, to maintain quiescent current between 5 and 10 mA, preventing thermal runaway inherent to bipolar devices. The prototype was constructed on a _Radio Shack universal board_ and achieved immediate operational success. The design requires a 15-volt Zener diode to protect the MOSFET gate from overvoltage. Component sourcing information is provided, including specific crystal frequencies (7.040 MHz or 7.122 MHz) available from _Dan’s Small Parts & Kits_ or Doug Hendricks. The fixed frequency can be slightly adjusted with a trimmer capacitor. A complete bill of materials, including resistor values, capacitor types, toroid specifications, and transistor part numbers, is detailed, alongside a clear schematic diagram.

Demonstrates building a basic _VOX circuit_ to add voice-operated transmit functionality to HF transceivers that lack this feature. The design utilizes a _1458 dual op-amp_ (two 741 op-amps in one package) to amplify microphone audio and act as a comparator, driving an NPN switching transistor for PTT control. A capacitor, C2, provides the necessary delay before unkeying the PTT, with a variable resistor, R6, allowing adjustment of the VOX level for specific microphones or voices. This low-cost circuit, detailed with a full parts list, offers a practical solution for hams seeking to enhance their budget HF rigs. The author, N1HFX, provides guidance on initial setup, including advice on microphone gain and the use of headphones to prevent speaker audio from re-keying the transceiver. Modifications for adjusting delay time are also included, suggesting increasing R8 to 10K for more delay or decreasing C2 to 22µF for less.

HF QRP Linear Amplifier with 2x 2SC2166 + 2x 2SC1969 Push Pull Transistors (13.8V)

Communication Concepts, Inc. specializes in providing RF components for both amateur radio operators building their own gear and professionals prototyping circuit designs. The inventory includes a range of products such as HF and VHF amplifiers, splitter combiners, and various filters, catering to diverse applications from QRP to high-power systems. The site details specific components like _Freescale_ and _Motorola_ RF transistors, along with custom semi-rigid coaxial cable options. The offerings extend to parts for ATV, packet radio, and general electronic components, emphasizing quality and service since 1979. Customers can find items like low-pass filters for RFI/TVI mitigation and specialized transformers for RF power systems, covering frequencies from 2-30 MHz Type "H" to 1-80 MHz high-power applications. The resource highlights its role as a supplier for those constructing custom radio equipment, offering components that facilitate projects from basic radio kits to advanced amplifier designs, with a focus on enabling self-construction and cost-effective prototyping.

Demonstrates the construction of two distinct wideband RF preamplifiers, detailing their component requirements and performance characteristics. The first design leverages monolithic microwave integrated circuits (MMICs) such as the MAR-6, MAR-8, or PGA103, offering a broad frequency response from DC to 2 GHz with a gain of 22.5 dB at 100 MHz and a noise figure typically below 3 dB. This MMIC-based amplifier incorporates protection against power supply transients and features a 50 Ohm input/output impedance, operating from an 8-20 volt supply with low current drain. The second preamplifier design utilizes a BSX-20 transistor, providing amplification across the 14 MHz to 550 MHz range. This simpler, more economical build achieves an average gain of 12 dB at 145 MHz and a noise figure of approximately 1.1 dB. It operates from a 7-15 volt battery supply with a current draw of 6 mA. Both projects emphasize critical construction techniques, such as maintaining short RF connections, ensuring 50 Ohm impedance paths, and mounting the circuit within a shielded enclosure to optimize performance and minimize noise. The resource also discusses phantom power options for antenna-mounted preamplifiers and precautions for use with transceivers, including output protection diodes and static bleeders.

A VHF power amplifier made with two cheap RF transistors, 2N3924 as driver and a BFS22A for final stage, giving an unexpected output power of 7-8 watts maximum

This resource, "Transistor Audio Preamplifier Circuits," offers comprehensive design guidelines for constructing **bipolar transistor** audio preamplifiers. It delves into critical aspects such as quiescent current setting, voltage gain calculation, and the impact of various component choices on circuit performance. The content provides several _schematic diagrams_ illustrating different preamplifier configurations, including single-stage common emitter and two-stage designs, alongside explanations of their operational characteristics and practical implementation considerations. The analysis extends to frequency response, noise performance, and distortion, providing insights into optimizing these parameters for specific audio applications. The resource presents calculated gain figures for various stages, demonstrating how to achieve desired amplification levels. It also discusses the importance of proper power supply decoupling and input/output impedance matching, crucial for integrating these preamplifiers into larger audio systems or ham radio transceivers. The practical application of these designs is evident in their suitability for microphone preamplifiers or general-purpose audio amplification.

There is not a personal design on this page, just I've transfered useful notes from PHILIPS RF Bipolar Transistors - Data HandBook about BLY89C VHF Power transistor, which is very popular among Amateur Radio homebrewers

Hi-Z Antennas offers specialized high-impedance receiving systems, primarily focusing on phased vertical arrays for HF reception. Their product line includes preamplifiers designed for shortened vertical antennas, featuring optimized 15dB gain and array-matched characteristics. These components are engineered to enhance weak signal reception and improve signal-to-noise ratio across the HF spectrum. The company provides controllers for managing multiple vertical elements in a phased array configuration, enabling directional reception patterns. These systems are particularly effective for mitigating local noise and interference, a common challenge in urban and suburban operating environments. Specific offerings include solutions for 160-meter and 80-meter bands, addressing the unique requirements of low-band DXing. Technical details often reference components like the 2N3866 transistor in preamp designs and discuss concepts such as out-of-band attenuation. The focus remains on optimizing receiving antenna performance through impedance matching and active amplification, rather than transmit capabilities.

Constructing a high-power 70cm solid-state amplifier presents unique challenges, particularly when aiming for 500 watts output using modern LDMOS devices. This resource details the author's experience building a 70cm amplifier based on a _Freescale MRFE6VP5600H_ transistor, initially from an RFHAM kit. It meticulously outlines the necessary modifications to achieve advertised performance, including optimizing input and output matching, correcting bias circuitry, and ensuring proper output balun connections for stability. The author shares specific adjustments, such as trimming the prototyping board for better transistor fit, drilling additional mounting holes for improved heat sinking, and replacing original matching capacitors with a single _20pf MIN02 metal mica_ for superior output. A critical fix involved jumpering gate decoupling pads to balance the push-pull transistor halves, which increased output to 580W and improved IMD. The resource also highlights a crucial correction to the output balun connection, initially reversed in the _Dubus_ article schematic, which resolved intermittent stability issues. Test results are provided, showing input power, output power, and drain current at 50V, demonstrating the amplifier's performance after modifications. This practical account offers valuable insights for hams undertaking similar high-power UHF amplifier projects, especially those working with LDMOS devices and kit-based constructions.

Operating the _Icom IC-746_ HF/VHF transceiver often presents specific technical questions, and this resource compiles a comprehensive Frequently Asked Questions (FAQ) document in an ASCII text format. It details common inquiries and solutions related to the rig's functionality, accessories, and potential modifications. The content is structured into distinct sections addressing general information, power supplies, antennas, microphones, keyers, amplifiers, TNC integration, and optional IF filters. The FAQ provides practical guidance on topics such as configuring the internal automatic antenna tuning unit (ATU), selecting appropriate power supplies, and understanding microphone pin-outs. It also delves into advanced subjects like computer control via CI-V, wiring for PSK31 operation, and troubleshooting common issues like low S-meter readings on 2m FM or loose tuning shafts. Specific questions cover the installation of optional IF filters, comparing Inrad versus Icom filters, and optimizing filter combinations for various modes. Furthermore, the document outlines various hardware and firmware modifications, including those for increasing monitor volume, replacing LCD driver transistors, and implementing a "poor man's TCXO." It even touches upon untested modifications, such as replacing PIN diodes in the demodulator. The FAQ also lists manual errata and discrepancies, offering a robust knowledge base for IC-746 owners seeking to optimize their station or resolve operational challenges.

A 600W 1.8 MHz to 54 MHz power linear amplifier made using rugged MRF300 transistors featuring output power between 580W and 750W depending on band, power supply: 48V, 18A typical, 20A max

A 144MHz FM class C RF Power Amplifier based on a 2N6084 RF transistor, that can produce 50w output max

The N1HFX thermal cooling fan controller project details a practical circuit designed to manage cooling fan operation based on temperature, a common requirement for high-power amateur radio equipment. This build utilizes a **LM34** temperature sensor, providing a linear voltage output directly proportional to Fahrenheit degrees, simplifying the control logic. The circuit's core functionality involves a comparator that activates the fan when a preset temperature threshold is exceeded, ensuring efficient cooling and reducing unnecessary fan noise. This controller is particularly useful for amplifiers, power supplies, or transceivers that generate significant heat during operation. The design incorporates a _TIP120 Darlington transistor_ to drive the fan, capable of handling up to 5 amps, making it suitable for a range of fan sizes and current requirements. Field results indicate stable temperature regulation, preventing thermal runaway in enclosed environments. Construction involves readily available components, making it an accessible project for hams looking to optimize their station's thermal management.

This is a Solid State Amplifier Project. It uses 4 MRF150 MosFet Power Transistors. The Power Supply Voltage is 50 VDC at 21.5 Amp. The max power available is 1,075 Watts. The Efficiency is about 65% +/- and runs Class AB Solid State.

This page details my building of a 100 Watt Power Amplifier for the 432 MHz Band based on two Motorola MRF646 transistors taking inspiration by Carlo Gnaccarini VK3PY, formerly VK3BRZ

The MiniPA Linear Amplifier for HF page discusses the popularity of QRP for HF among ham radio operators, such as those using the Yaesu FT818 or low power SDR transceivers. It explores the use of cheap kits from eBay or Chinese suppliers to build a 70-100W SSB amplifier using IRF530 MOSFET transistors. The article provides a review of the MiniPA design, including its features, components, and assembly process. It also highlights the importance of using a heatsink and forced air cooling for optimal performance. This page is useful for hams looking to enhance their HF rig with a budget-friendly amplifier.

This page by Lajos Hoss, HA8HL, provides a detailed guide on how to build a simple direct receiver using FT8QRP CAT control support. The author shares his experience in making QSOs with FT8, WSPR, and JT65 modes during the Covid-19 lockdown. Modifications to the VFO, transmitter design using BD329 transistor Class A amplifier, and the challenges faced in achieving clean output signals within legal limits. This project is interesting for those hams that are interested in experimenting with DIY transmitter projects and understanding CAT control support for various amateur radio modes.