The above 7 Mhz 5 Watts CW Transmitter circuit was found in one of back issues of sprat. Still i am wondering how 5 watts juiced out from this tiny crystal oscillator circuit. This classic 7 MHz CW Transmitter circuit demonstrates how effective amateur radio equipment can be built with minimal components and straightforward design […]
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
Circuit – FM Bandstop Filter for RTL SDR
FM Bandstop Filter for RTL SDR The given FM band stop filter is nothing more than a simple Band stop filter for the frequency range of 88-108Mhz. FM Broadcast transmitters transmit at high power and can cause overloading and intermodulation problems on simple receivers like RTL-SDR due to its wide open front end. The said […]
Circuits – Simple zener diode tester
Simple zener diode tester Ever found yourself with a handful of zener diodes, wondering if they’re still good or what their actual breakdown voltage is? Zener diodes are incredibly useful components for voltage regulation, but sometimes, their markings can be ambiguous, or you just need to quickly verify their functionality. That’s where a simple zener […]
Circuits – 7MHz CW / AM QRP Transmitter
Build a versatile 7MHz QRP Transmitter capable of both CW and AM modulation. This DIY guide features a stable 40-meter crystal oscillator, a class-C power amplifier, and simple switching for dual-mode amateur radio operation.
Circuits – Offset tuning indicator for CW
An NE567 tone decoder, tuned to the transceiver`s CW offset frequency, ensures that the transceiver will be transmitting on the same frequency as the received CW signal. Simply tune the transceiver so that the LED lights. Eight to 13 Vdc is required; this can be taken from the transceiver supply or an extra battery. Audio […]
Circuits – Simple tester checks LCDs
Manufacturers of electronic equipment use LCDs for calculators, watches, mini-videogames, and pagers, for example. In comparison with LED-based displays,which consume power on the order of tens of milliwatts, an LCD consumes only a few microwatts. The LCD thus saves power by a factor of approximately 1000. Checking an LED is as simple as checking a […]
Circuits – White LED Torch
This white led torch circuit provides an effective solution for powering white LEDs. It is ideal for flashlights, emergency lighting, and various other applications. The circuit operates efficiently from one or two primary cell batteries. The core of the circuit involves a transistor (Q1) and a tapped inductor, forming a blocking oscillator. When the power […]
Circuits – Dark Room Timer
The Dark Room Timer circuit described here provides a pleasant musical tone in your darkroom at 1-second intervals. The circuit takes up very little space and can be easily converted into a metronome. Unijunction transistor T1 functioning as a relaxation oscillator triggers phase-shift audio oscillator circuit turning it on and off. Capacitor C1 is charged […]
Do it yourself Shortwave Transmitter circuit
This Shortwave Transmitter circuit operates in shortwave HF band (6 MHz to15 MHz), and can be used for short range communication and for educational purposes. The Shortwave Transmitter circuit consists of a mic amplifier, a variable frequency oscillator, and modulation amplifier stages. Transistor T1 (BF195) is used as a simple RF oscillator. Resistors R6 and […]
Circuits – Check Digital Or Linear Circuits With The Flick Of A Switch
A simple logic probe in concert with a signal source can be used to check digital as well as linear circuits. With the flick of a switch, the probe can inject a test signal or check the logic state of a digital signal. Comprising just one CMOS IC (CD4011B) and a handful of components, the […]