Mainly f. m. receivers are of the superhetrodyne variety. Before we go into any depth about f. m. radio receivers let`s consider the principal differences between a. m. and f. m. signals. At first glance it might seem I am merely stating the blinding obvious but the differences are indeed quite profound. An a. m. receiver relies upon the original carrier signal (station frequency)
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having been amplitude modulated. This means the original amplitude (strength) varies at an audio rate. Looking at figure 1 we can see an unmodulated carrier signal as it might be seen on an oscilloscope. as you can see the amplitude of the carrier signal is unvarying, it remains constant in height looking from the top of the figure to the bottom of the figure. This carrier is common to both a. m. and f. m. signals. Perhaps the a. m. carrier signal repeats each cycle from point (a) to point (b) - "blue" - in figure 2 below at the rate of 810, 000 times a second, this represents a frequency of 810 Khz and would be in the a. m. radio band. Here you will notice that the audio modulating signal which is depicted in red has varied the strength of the carrier signal which is depicted green for purposes of this illustration. You will note my skills as a graphic artist leave much to be desired (hint: anyone able to contribute oscillograghs in. jpg or. gif formats ) but you should be able to see the carrier sine wave envelope is being varied in strength by the red audio signal. In the receiver circuit a diode detector can convert that envelope above back into the original audio signal for later amplification although some distortion does result. It was to an extent this distortion property that people sought a better means of transmission. More important it was discovered that noise (either man made QRM or natural noise QRN) was...
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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