The old common-base audio preamp, having a noise figure of 5dB is an obvious target to improve the noise figure. A common-emitter configuration, with shunt feedback gives 50 ohms input resistance (preferred by the mixer) and a 2dB noise figure. Two paralleled 2N4401 transistors results in better noise performance at such a low input impedance. A g
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ain of 60 masks most of the noise in the op-amp phase shifter that follows. Common collector ouput stages provide a low output impedance needed to drive the audio phase shifter. A simpler diplexer between mixer and preamp shaves a little off the noise figure too. Rick`s R2 diplexer has steeper stopband slope, but about 2dB loss. The TOKO 10RB inductors simply have too much series resistance: I wound my own on small potcores, 14x8 mm. The potcore bobbins are very easy to wind, but its tricky to get the inductance exact - too much pressure from a mounting screw can change inductance dramatically. Potcore mounting hardware from the manufacturer is recommended. The 1. 2mH inductor should have low internal capacitance - 35 turns #32 wire in a single layer on a FT37-77 ferrite toroid. Diplexer low-pass frequency at 6700 Hz. , and high-pass frequency at 170 Hz are outside the audio passband (350 - 3500 Hz. ). This means that unwanted phase shifts from mismatched diplexer parts are less troublesome, relaxing the need for extremely accurate component values. With the tuning method described below, some of the bad effects of mismatched components can be tuned out. Nevertheless, diplexer components were matched with the aid of a commercial Maxwell impedance bridge. The phasing R`s and C`s were all scaled so that resistor values were much smaller. Otherwise, the Johnson noise from those warm, large value resistors adds so much noise...
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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