Simple 2N3904 microphone preamplifier for uBITX V3–V6 transceivers that fixes low mic audio and restores full transmit power. Powered from the MIC+ line with adjustable gain for clean, natural SSB modulation.
Circuits
The Circuits category focuses on stand‑alone electronic building blocks that power your radio and audio projects: amplifiers, oscillators, filters, keyers, indicators, test jigs, and more. Instead of full transceivers or big systems, you’ll find focused designs like microphone preamps, push‑pull HF linear amplifiers with IRF510, regenerative receivers, short‑wave transmitters, low‑battery indicators, and timing circuits
DIY HF Linear Push-Pull Amplifier with IRF510 MOSFETs
Learn how to build a high-performance HF Linear Push-Pull Power Amplifier using affordable IRF510 MOSFETs. This guide includes a full schematic, bias adjustment tips, and transformer winding details for 10-40W output across the HF bands.
Build a High-Sensitivity Regenerative Receiver with 2N7000 MOSFET
The 2N7000 regenerative receiver is a classic single-transistor radio that combines simplicity with surprisingly high sensitivity. By using controlled positive feedback, the circuit operates just below oscillation, dramatically increasing gain and selectivity.
Mighty Mite 5W Crystal Controlled QRP CW Transmitter
The Mighty Mite 40 Meter QRP CW Transmitter is a legendary low-power Morse code transmitter widely built by amateur radio operators for portable, minimalist, and educational operation.
Building Sovina 40M Class E CW Transmitter with BS170 MOSFETs
Build the Sovina 40 m Class-E CW transmitter using BS170 MOSFETs and 74HC02 logic for efficient 7 MHz QRP operation. High-efficiency switching PA delivers 4–7 W output with clean RF and simple crystal-controlled design for homebrew HF rigs.
Build a Powerful FM Radio Bug Transmitter
Three-stage FM bug transmitter using BC547 audio preamp, RF oscillator/modulator, and 2N3563 power amplifier for strong 100 MHz transmission. High-performance DIY wireless microphone circuit with improved range and signal stability.
Microphone Pre-Compressor Circuit for SSB Transceivers
Clean, punchy audio is critical for effective SSB communication, especially when operating QRP or low-power HF transceivers. A microphone pre-compressor placed ahead of the transmitter’s audio input can significantly improve average modulation levels without introducing harsh distortion. The attached Microphone Pre-Compressor circuit is a practical, discrete-component design well suited for homebrew and experimental SSB rigs.
Simple Speech Processor for Homebrew SSB Transceivers
Simple speech processor for homebrew and QRP SSB transceivers that boosts average talk power while preserving natural audio. BF245 mic preamp, dynamic compression stage, and TL071 output amplifier improve readability and on-air presence.
Microphone Preamplifier with Diode Clipper for SSB Transceivers
Simple microphone preamplifier with diode clipper to boost and limit SSB audio for amateur radio transceivers. Prevents over-modulation, improves speech clarity, and delivers clean transmit audio in DIY HF radio setup
DIY 1 MHz AM Transmitter: A Perfect Weekend Project for Beginners
Basics of radio frequency by building a simple 1 MHz AM Transmitter. This guide explains the circuit design and secrets of amplitude modulation for hobbyists