Showing posts with label Frequency. Show all posts

50MHz-300MHz Colpitts Oscillator

In this electronic project circuit you can see a very simple high efficiency Colpitts oscillator. In the higher frequency ranges, above 50 MHz, Colpitts oscillators are used because stray circuit capacitance will be in parallel with desired feedback capacitance and not cause undesirable spurious resonances that might occur with the tapped coil Hartley design. The FM VCO shown is a grounded base design with feedback from collector to emitter.

50MHz-300MHz Colpitts Oscillator Circuit Diagram:

A Colpitts oscillator is one of a number of designs for electronic oscillator circuits using the combination of an inductance with a capacitor for frequency determination. The distinguishing feature of the Colpitts oscillator circuit is that the feedback signal is taken from a voltage divider made by two capacitors in series. As you can see in the circuit diagram , this electronic project require few electronic parts an provide a 50 MHz-300MHz VCO with a tuning range of 2:1.

How to build a Long-range FM Transmitter

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How to build a Long-range FM Transmitter. The power output of most of these circuits is very low because no power amplifier stages were incorporated.

The transmitter circuit described here has an extra RF power amplifier stage, after the oscillator stage, to raise the power output to 200-250 milliwatts. With a good matching 50-ohm ground plane antenna or multi-element Yagi antenna, this transmitter can provide reasonably good signal strength up to a distance of about 2 kilometres.

Long-range FM Transmitter Circuit Diagram

The circuit built around transistor T1 (BF494) is a basic low-power variable-frequency VHF oscillator. A varicap diode circuit is included to change the frequency of the transmitter and to provide frequency modulation by audio signals. The output of the oscillator is about 50 milliwatts. Transistor T2 (2N3866) forms a VHF-class A power amplifier. It boosts the oscillator signals’ power four to five times. Thus, 200-250 milliwatts of power is generated at the collector of transistor T2.

For better results, assemble the circuit on a good-quality glass epoxy board and house the transmitter inside an aluminum case. Shield the oscillator stage using an aluminum sheet.

Coil winding details are given below:
L1 - 4 turns of 20 SWG wire close wound over 8mm diameter plastic former.
L2 - 2 turns of 24 SWG wire near top end of L1.
(Note: No core (i.e. air core) is used for the above coils)
L3 - 7 turns of 24 SWG wire close wound with 4mm diameter air core.
L4 - 7 turns of 24 SWG wire-wound on a ferrite bead (as choke)

Potentiometer VR1 is used to vary the fundamental frequency whereas potentiometer VR2 is used as power control. For hum-free operation, operate the transmitter on a 12V rechargeable battery pack of 10 x 1.2-volt Ni-Cd cells. Transistor T2 must be mounted on a heat sink. Do not switch on the transmitter without a matching antenna. Adjust both trimmers (VC1 and VC2) for maximum transmission power. Adjust potentiometer VR1 to set the fundamental frequency near 100 MHz.

This transmitter should only be used for educational purposes.

Video Signal Amplifier Using with LH0024

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Overview
The construction of the circuit has been increased to highlight and amplify video signals for further frequencies on image clarity.

Video Signal Amplifier Circuit diagram

Terminology

LH0024 – IC small signal IC designed for general purpose switching and amplification due to its low voltage, low voltage and three different win the election 1N4148 – silicon small signal diode planar epitaxial used for fast switching applications with a reverse voltage of 100 V and forward current of 150 mA

Circuit Explanation

In a video output signal is the high rate of frames selected for amplification of producing a finer. This is possible by placing the track between the video device and the reception lobby, where the video port of the television receiver is inserted. The construction is done simply by exploiting the operation of three transistors instead of IC and other supporting elements.

An isolator operating in the first phase of the Q1, which provides an interface for input impedance. Q2 manage the second phase, which leads to the common base configuration. In this phase, determine the earnings TR2 250 ohms cutting the lawn. To adjust TR2, it must be placed where an output voltage of 1 Vp-p is present, with a load of 75 ohms. The frequency response is regulated by a combination of R6, C3, and 500 ohms TR1. An output buffer is completed by Q3 of the third phase which provides an airline pilot with 75 ohms. The range of the circuit is stabilized with 12 V and 50 mA.

Basic Monostable Using with LM555

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Welcome to free circuit dot com,For the last article in this series, we may be unstable a cycle which has no stable output state. In this post circuit we will show the monostable circuit, which has a stable state.

Basic Monostable Circuit diagram

The waveforms in Figure 1 show the effect of a monostable. A monostable circuit produces a pulse of a certain length (time T) in response to a trigger input such as a pushbutton. The output of the circuit remains in the low position to a trigger input, does the name “Mono”, “stable condition”. This type of circuit is ideal for use in a “push-to-operate” in a model system for exhibitions.

A visitor can press a button to a model mechanism in motion, and the mechanism will automatically after a certain time. Another use of the circuit “the bounce” an important contribution to a digital IC – this application will be explained later in this article.