Circuits – 40M tag QRP Transmitter
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.
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Circuits – Simple zener diode tester
Simple zener diode tester Circuit – FM Bandstop Filter for RTL SDR
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 onlya few microwatts. The LCD thus saves power by a factor of approximately 1000. Checking an LED is as simple as checking a semiconductor …
Circuits – White LED Torch
This low-cost circuit is suitable for powering flashlights, emergency lighting and other applications in which it is desirable to power white LEDs from one or two primary cell batteries. The transistor, lk resistor [Rll and the tapped inductor form a blocking oscillator. When the power button is pressed, the transistor …
Circuits – DARK ROOM TIMER
The 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 (UJT) T1 functioning as a relaxation oscillator triggers the phase-shift audio oscillator circuit built around transistor T2, turning it on and off. As …
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 …
Circuits-VHF Preamplifier using Max2633
Here is a high performance RF amplifier for the entire VHF band that can be successfully built without any special test equipment. The grounded -gate configuration is inherently stable without any neutralisation if reasonably good layout techniques are employed. The performance of the amplifier is quite good. The noise figure is below 2dB and the …