DIY Antennas, QRP, SDR & Ham Radio Projects from VU3DXR
Explore homebrew RF transmitter on DXR Electronics Bits, including QRP CW transmitters for 40 m/80 m, AM medium-wave and 27 MHz transmitters, FM bug and wireless microphone circuits, and MOSFET Class-E power stages. Learn oscillator stability, modulation techniques, RF filtering, and practical transmitter construction for amateur radio and electronics experimentation.
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.
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
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.
This is a Class E Transmitter designed for the 40-meter amateur radio band, capable of producing approximately 4.6W output power at 80% efficiency. Class E Transmitter Power Supply 11.5V DC supply (Vcc) powers the circuit 470µF electrolytic capacitor provides power supply filtering and decoupling Input Stage 1M input resistor provides high impedance input matching 10µH […]
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 […]
Here is another qrp cw transmitter pulled out from SPRAT back issues, which is simple to build with commonly available components from every one shack. We can subsititute 2N2222 for BC108 and BD139 for BD 131.
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 […]