DIY Antennas, QRP, SDR & Ham Radio Projects from VU3DXR
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
The GM300 series radios are line of two-way radios manufactured by Motorola Solutions. They are popular choice for amateur radio operators due to its features, performance, and affordability. GM300 is also a very durable radio. It is built to withstand the elements and can handle even the most demanding conditions. Similarly, the Motorola GM338 is […]
VK3YE’s AGC circuit for ubitx An ubitx AGC board is a circuit board that can be installed in a ubitx transceiver to provide automatic gain control (AGC). AGC is a feature that automatically adjusts the gain of the transceiver’s amplifier to maintain a constant audio output level, regardless of the strength of […]
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 […]
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 […]
Simple Crystal tester – The idea for this crystal tester circuit sprung out of the need of testing a large number of oscillator crystals lying unused in a big hobby box. testing the crystals one by one without the appropriate device would have been very slow and a time consuming task. Commercial crystal testers are […]
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 […]
This is a clever Battery low power indicator circuit designed by G3AGX that provides a visual indication when equipment is drawing power, even at very low current levels. The circuit is particularly useful for monitoring standby power consumption or confirming that equipment is actually powered on. Battery Low Power Indicator Circuit Analysis The heart of […]