DIY Antennas, QRP, SDR & Ham Radio Projects from VU3DXR
The QRP section is dedicated to low‑power HF and VHF operating, with a heavy focus on simple transmitters, minimalist transceivers, and practical on‑air results. Here you’ll find classic designs like the Mighty Mite, OXO transmitter, Mosquito TRX, and modern SDR‑based rigs such as sBitx and ZBitx tuned for portable use, all built around parts that are easy to source and experiment with. Articles emphasise repeatable circuits, clean keying, stable oscillators, and output filters so that your 1–5 W signal is both efficient and pleasant to copy at the other end
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 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
This series-modulated AM transmitter uses a simple low-power design where the audio signal is applied directly to the power supply of the RF oscillator, causing the carrier amplitude to vary and produce AM. It uses a crystal oscillator for stable frequency and is ideal for beginners learning basic radio transmission concepts.
This Class C AM transmitter uses a high-efficiency amplifier where the transistor conducts for less than half the signal cycle, achieving around 70–80% efficiency. It combines an oscillator, buffer, and IRF510 MOSFET power stage to deliver about 5 W RF output, making it suitable for compact amateur radio transmission.
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.
Build a functional “Ten-Minute” QRP Transmitter with this simple DIY guide. Featuring a minimal component count and a crystal oscillator, this ultra-fast build is perfect for beginners and ham radio emergency kits.
G4RAW 80M QRP CW Transmitter: The original version was built on tag strip, hence the name. For PA, we can use BD139 instead of 2SC2078. It should have good heat sink. The “G4RAW 80M QRP CW Transmitter” refers to a popular, simple, and low-power (QRP) Continuous Wave (CW) transmitter design for the 80-meter amateur radio […]
This pippin QRP transmitter is basically a conventional colpitts type crystal oscillator with output taken from a low value collector load resistor and direct coupling is made into the base of PNP transistor used as an amplifier. This simple circuit develops around one watt output with 12V as power supply. At the heart of this […]