Compact dual-band RW4HFN antenna covering 145 MHz (2 m) and 430 MHz (70 cm) with a center-fed element and integrated matching section. Single-feed 50 Ω coax design provides versatile VHF/UHF operation for base, portable, and repeater use.
Circuits
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
VHF Radio Receiver Antenna Amplifier Using MAX2633 – Simple Low-Noise RF Preamplifier Design
Build a low-noise VHF RF preamplifier using the MAX2633 MMIC to improve receiver sensitivity and antenna signal strength on 144–148 MHz. Simple biasing and matching provide wideband gain for FM, repeater, and weak-signal reception.
Mosquito TRX: Single-MOSFET 40-Meter (7030 kHz) CW Transceiver
Mosquito TRX is a single-MOSFET 40 m CW transceiver for 7030 kHz using crystal control and direct-conversion reception — an ultra-simple QRP rig and SDR front-end for sound-card radios
Curumim Transceiver – World’s Smallest QRP CW Transceiver
Discover the Curumim Transceiver, an ultra-minimalist QRP CW rig for 7.030 MHz that combines a single-transistor crystal oscillator and LM386 audio amplifier into one of the world’s smallest working HF transceivers, ideal for homebrewers, educators, and portable CW enthusiasts
The Simple RF Indicator: A DIY Tool for Detecting RF Signals
The image depicts “Simple RF Indicator,” passive device for detecting radio frequency (RF) signals in coaxial cables. It’s a clever hack using basic components
DIY Active Antenna: Boost Weak HF/VHF Signals
DIY Active Antenna for superior HF and VHF reception! This DIY electronics project amplifies weak signals to lift hard-to-hear broadcasts out of the noise
Build a DIY Ion Detector: Detect Airborne Ions and Electrostatic Emissions
Build a simple handheld DIY Ion detector circuit using transistors to detect air ions, static discharge, and emissions. Perfect for science electronics projects
Simple Incandescent Lamp Flasher Circuit Using 7555 Timer
Build a simple incandescent lamp flasher using a 7555 timer and MOSFETs. Ideal for DIY projects with adjustable flash rate and low parts count.
Tiny FM Transmitter with Just a Few Easy-to-Find Components
Learn how to build a compact Tiny FM transmitter using 2N3904, a few passive parts, and a simple air-core coil. Perfect for DIY electronics enthusiasts
27MHz AM Transmitter Circuit for hobbyists
The 27MHz frequency band has long been a favorite among electronics enthusiasts and amateur radio operators. This citizen’s band frequency offers excellent propagation characteristics and serves as an ideal starting point for understanding amplitude modulation (AM) transmission principles. Today, we’ll explore a well-designed 27MHz AM transmitter circuit that demonstrates classic RF engineering concepts while remaining accessible to hobbyists