DIY Antennas, QRP, SDR & Ham Radio Projects from VU3DXR
Technical guides and homebrew projects focused on amateur radio audio processing. Explore DIY builds for speech compressors, balanced modulators, and low-pass filters designed to enhance transmit clarity and receive intelligibility. From vintage microphone interfaces to modern digital signal processing, find the tools to optimize your station’s ‘talk power’ and audio fidelity
Learn how to build a simple and effective Audio Clipper Circuit using BC547 transistors and 1N914 diodes. This DIY guide covers schematic details, component selection, and how to prevent overmodulation in amateur radio transmitters for clearer, peak-limited audio.
The NJM4558 audio compressor represents one of the most reliable and widely-used integrated circuits in professional audio applications. Furthermore, this dual operational amplifier IC has become the cornerstone of countless audio compression circuits due to its exceptional performance characteristics and versatility. The NJM4558 audio compressor circuit shown in the schematic demonstrates a sophisticated approach to […]
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
The LM1458 is a dual operational amplifier (op-amp) that finds applications in audio amplification and other circuits. Let’s explore how you can create a simple Microphone compressor using the LM1458. To get greater transmitting performance from your ham radio transceiver, we need to keep the modulation level constant, regardless of your voice level. With the compressor […]
The compact, low-cost condenser mic amplifier described here give good-quality audio of 0.5 watts at 4.5 volts,used in walkietalkies, low-power transmitters
This dual-microphone noise cancellation circuit uses two microphones placed back-to-back, with one signal inverted and summed using an LF351 op-amp to cancel common ambient noise. It preserves the desired voice signal while reducing background noise, improving clarity in noisy environments
This dynamic speech compressor with audio preamplifier combines a transistor-based preamp and op-amp gain stage with diode-controlled compression to regulate signal levels. It automatically reduces loud peaks and boosts weak audio, delivering consistent output with adjustable threshold, attack, and release timing for clear speech and improved transmission quality.
Simple audio compressor for SSB HF Radio rigs An audio/speech compressor is a device that reduces the dynamic range of the audio signal. This means that it makes the loud parts of the signal quieter and the quiet parts of the signal louder. This can be useful for SSB HF radio rigs because it can […]
This article presents a simple, low-cost audio compressor circuit designed to stabilize microphone signal levels. It reduces dynamic range by softening loud sounds and boosting weak ones, improving clarity and intelligibility. Built with basic components, it suits amateur radio and DIY audio setups, offering consistent output without complex or expensive hardware.
LM386 Audio oscillator This one is excellent application of widely used audio amplifier IC LM386.Its output is square wave at no load condition. Its frequency is governed by supply voltage. It can be used as code practice oscillator, even as side tone for your qrp radio. The LM386 is an widely abused integrated circuit containing […]