The inductor is made by winding 8 turns of #24 insulated solid copper wire on a 5 mm screwdriver. I used a conductor from a piece of category 5 quad twisted pair, left over from wiring the house with Ethernet and this seems to work well and to be easy to handle. Stripping the vinyl insulation is much easier than scarping or burning off enamel.
This was easily tuned up and down the bottom of the FM band using a 10 turn panel mounted potentiometer. The upper limit to the frequency modulation is set by the 39 k input resistor and the shunt capacitance (I would guess around 20 pf max), so that shouldn't be a concern until the modulation frequency reaches many MHz.
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Build this on a ground plane board. Layout is important. If you place the parts relative to one-another in correspondence with their placement on the schematic, it should work pretty well. For making one or two of something, I don't like to bother with a printed circuit boards. I just cut off a 2.5 x4 cm piece of copper clad board and soldered grounded parts onto the copper cladding fiberglass, and the ungrounded parts directly onto the leads of the grounded parts. This "dead bug" construction is a very speedy way to put high frequency circuits together and it works pretty well at these frequencies. One thing to be careful of is to make sure all the components are packed tightly so as to minimize parasitic resulting from long leads. In the ones I built, the components are leaded, though in one of them I used chip capacitors for the bypass capacitors, though I couldn't see any difference in performance.
It was necessary to shield the circuit so that it would not be affected by other circuits nearby, particularly additional RF stages. The loose coupling for the RF, provided by the 330 build-out resistor on the emitter follower further serves to isolate the oscillator from its load. These result in greater stability. The shield was made by forming a five-sided box (one side missing) from tooling copper (a thin copper sheet) and soldering it onto the groundplane of the copper clad board. Once, for something similar, I made a...
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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