Three-stage active Butterworth bandpass input filter is used in radioteletype demodulator to separate RTTY tones from each other and from noise. Filter is centered on 2200 Hz, and has bandpass of about 260 Hz to allow reception of some of audio sidebands produced by keying and allow for small drift. Five pots serve for trimming center frequency of
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each stage andQ of end stages. Article gives step-by-step design and alignment procedures. Use two 10K resistors between V and ground to get V/2 for bias when operating from single supply. -P. A. Stark, Design an Active RTTY Filter, 73 Magazine, Sept. 1977, p 38-43. (View) Triggering is accomplished by turning transistors on, whereas in most similar circuits the transistors are turned off. Trigger pulse merely has to lower point o below ground for fraction of microsecond. Almost any diode and transistor can be used. Speed can be up to 10 Mc with high-speed transistors. Output fall time is fast. -Binary Flip-Flop Tums On, Electronic Circuit Design Handbook, Mactier Pub. Corp. , N. Y. , 1965, p 214. (View) Simple circuit for Signetics NE565 PLL locks to input frequency and tracks it between two values used, to produce corresponding DC shift at output. Values shown are for 1070-Hz and 1270-Hz FSK signals. Three-stage RC ladder filter removes sum frequency component. Band edge of filter is chosen to be about halfway between maximum keying rate (150 Hz) and twice input frequency (about 2200 Hz). Output is made logic-compatible by connecting voltage comparator to pin 6. - Signetics Analog Data Manual, Signetics, Sunnyvale, CA, 1977, p 845. (View) Cross-coupling of two basic inverters gives low-cost lip-lop using 2N711 germanium pnp mesa switching transistors. Flip-flop can be set and then reset, or run as Gaunter using combined...
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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