After I built my KN-Q7 kitset 40m QRP single sideband (SSB) transceiver, described elsewhere on this site, I went on to build a matching low power `Z-match` antenna tuner and a sensitive SWR meter. For some reason, I found I needed three hands to tune this apparently simple arrangement One hand to hold the PTT button down, and then two more ha
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nds to simultaneously adjust the controls on my antenna tuner, while simultaneously whistling into the microphone, after delivering the essential voice station identification, of course! For those new to ham radio, an audio tone or a reasonably continuous level of speech is required into the microphone so an SSB transmitter will generate some RF power. That RF power allows the SWR meter to measure the match between transmitter and antenna, and determine when the antenna tuner is correctly adjusted. My problem didn`t stop with the lack of three hands. A really bad cold had left me with a decided lack of "whistle-power". Those who suffer from asthma can probably appreciate this latter problem all too well. Adding a tone oscillator into the KN-Q7 QRP transceiver would have solved the problem, but space inside that radio is very limited. This external TuneAid oscillator was my solution. The TuneAid is a simple combination of a timer and audio tone oscillator. It`s a 100% discrete parts design, built with common small signal audio PNP and NPN transistors. The circuit diagram is shown in Figure 1. Pressing pushbutton SW1 turns on Q1. This then turns on the oscillator (Q3 and Q4). With C1 initially discharged, Q2 is turned hard on, keeping Q1 turned on after pushbutton SW1 is released. So, only a brief press of the power-on switch is required to start the tone generator. C1 slowly charges through R4, steadily reducing the voltage...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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