DIY Antennas, QRP, SDR & Ham Radio Projects from VU3DXR
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
Solar cells can easily provide enough power to operate a small radio receiver. This DIY Solar Powered Radio project is an ideal set to take away on holiday. It covers the medium wave (AM) waveband, so why not laze on the beach this summer and listen to your favourite station. But first, let’s get busy with […]
Ham Radio Repeater Toneburst Module generates a precise 1750Hz toneburst lasting 0.5 seconds, essential for accessing UK and European amateur radio repeaters.
This audible continuity tester uses a simple oscillator IC to generate a tone when a closed circuit is detected. Powered by a 1.5V battery, it provides instant audio feedback for testing wires, fuses, PCB traces, and connections, making troubleshooting faster and hands-free.
This simple sine wave oscillator uses a transistor-based phase-shift network to generate a clean periodic signal, then amplifies it with an LM386 for usable output. It runs on a 9V supply and suits audio testing, tone generation, and learning oscillator fundamentals
This TL071 audio compressor circuit uses a single-supply design with a TL071 op-amp as a voltage-controlled amplifier to manage audio levels. It includes input coupling, peak detection, and RC timing networks to control compression, delivering stable, low-noise dynamic range control for audio and radio applications.
This simple AM transmitter uses a crystal-controlled oscillator and transistor stages to generate and amplify a stable RF signal, then modulates it with audio through a transformer. Powered by 12V, it offers a practical introduction to radio transmission using basic, easily available components.
This microphone audio compressor uses an LM324 op-amp with multi-stage amplification, diode-based gain control, and buffering to regulate signal levels. It smooths volume by reducing loud peaks and boosting weak input, improving clarity for voice, recording, and radio applications with a stable 12V supply
This FT8 digital interface connects a computer to a transceiver using a USB sound card, audio transformers, and optocoupler-based PTT control. It enables clean audio exchange and safe isolation, allowing reliable weak-signal digital communication modes like FT8 through proper level control and synchronization.
This simple CW transmitter uses a 74HC240 buffer IC as both oscillator and driver to generate a stable RF signal around 7.023 MHz. A crystal ensures frequency accuracy, while keying enables Morse transmission, making it a compact, low-power QRP project for beginners.
This micro power AM transmitter uses a crystal-controlled oscillator and a 2N2222 transistor stage to generate a stable RF carrier, then modulates it with audio input. A tuned tank circuit and variable capacitor optimize output, enabling low-power short-range broadcasting for experimentation and learning