DIY Antennas, QRP, SDR & Ham Radio Projects from VU3DXR
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.
This simple two-stage AM transmitter uses an oscillator and a transistor RF amplifier to deliver about 1 W output on HF bands. It supports common transistors like BD139 or 2N3553, uses a modulation transformer for audio input, and serves as a beginner-friendly QRP project with stable performance
Build a Simple Series Modulated AM QRP HF Transmitter for the 40m or 80m bands. This DIY guide includes a stable crystal oscillator schematic, series modulation tips, and power amplifier details for low-power (QRP) ham radio operation.
Looking for a fun weekend project? Discover the OXO QRP transmitter—an elegantly simple, high-performance HF rig perfect for homebrew enthusiasts and minimalist radio operators
Stop fading into the noise! Build this simple, low-cost speech compressor using the LM324 quad op-amp to ensure your voice stays loud and clear on the airwaves.
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.
This article describes a simple microphone compressor built with three transistors to improve audio consistency. The circuit uses a preamplifier, buffer, and feedback stage to control gain. As input increases, negative feedback reduces amplification, compressing louder signals. It runs on 12V and suits amateur radio setups needing stable, balanced voice output.
This project uses an SSM2167 IC as a complete microphone preamplifier with built-in compression and noise gating to improve uBITX transceiver audio. It boosts mic gain, reduces dynamic range, and suppresses background noise, resulting in clearer, louder, and more consistent transmitted speech.
This article explains how to build a low-cost ribless programming cable for Motorola GM360, GM338, and GM300 radios. It uses a USB-to-TTL adapter, RJ45 connector, and a diode to enable direct serial communication without a RIB unit. The guide covers wiring, setup, and software configuration for reliable radio programming.
1:49 UNUN is a type of transformer that can be used to match an end fed half wave antenna to a 50 ohm coaxial cable. It is made from two stacked FT240-43 cores.