The regenerative detector uses a field effect transistor (FET). Like with the better valve designs, feedback is controlled by a variable capacitor. A ferrite rod was used to allow reception of local stations without an external antenna. This FET stage forms a complete receiver on its own, but the audio output is quite low. The received audio is amplified by an NPN bipolar transistor. The gain of this transistor amplifier is sufficient to provide speaker reception of local stations in most areas. The 1k to 8 ohm transformer in the collector allows the set to be used with both low and high impedance headphones.
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The aim of this project was to develop a simple receiver that could be built with readily obtainable parts. With the partial exception of the main tuning capacitor, this has been achieved. A 10 to 415 pF variable capacitor was used as the main tuning capacitor. These are found in valve radios and early transistor sets. They are rare new but are still common at hamfests. Their wide tuning range make it possible to cover the AM broadcast band and 160 metres without having to sacrifice coverage of the bottom end of the broadcast band. The long shafts of these capacitors also make them easier to use with vernier dial drives. Some constructors may wish to build their set now without waiting for the next hamfest. The first version of the Moorabbin used a 60/160pF plastic tuning capacitor (same as the regeneration control) instead of the 10-415 pF unit substituted later. Receiver performance with the plastic capacitor was good. The main difficulty encountered was coupling it to the vernier dial. This was overcome by extending the shaft with a 2.5 mm diameter screw and a spacer. To compensate for the lower maximum capacitance, more turns need to be wound on to the ferrite rod to cover the whole broadcast band. Details on this are given later. It is possible to get by without a vernier dial, but using the set will not nearly be as enjoyable, especially if you want to hear more than just the local stations. Though expensive, it is...
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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