Showing posts with label Radio. Show all posts
Thursday, June 20, 2013
Two Stage FM Transmitter
After a two months we are back with a Simple and Working FM Transmitter Circuitry.This a two stage FM Transmitter which is in work fine and you can use it to transmit your signal over a long distance,Its work within 100 meters to 2-3KM.Frequency Range is 87.5MHz to 108MHz.For transmitting over a 2-3KM,its require a minimum 75cm antenna height.Increasing a antenna height will always give us a better range but 2-3KM Transmission is sufficient for smaller projects and increasing height will cause a circuit unstable so please keep your antenna height in between a 75cm-100cm.
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Filed Under:
hobby project,
Radio
Wednesday, April 18, 2012
Wideband FM Jammer
How Its Work Or Operation Principle:
Sawtooth and white-noise signal generator:This wideband jammer simultaneously blocks all transmissions within a desired band typically by "sweeping" across the desired band to be blocked, starting at the lowest frequency and ending at the highest frequency of the band. For this purpose a linear sawtooth signal is applied to the modulator in the FM transmitter described here. The transmitter uses varactor diodes in the tuning circuit to determine the transmitters frequency of operation.Applying a sawtooth signal to the varactor diodes results in the transmission frequency changing with respect to the changing voltage of the sawtooth. As the voltage of the sawtooth signal increases so does the frequency at which the transmitter transmits. This cycle is repeated many times a second.
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Filed Under:
Radio
Thursday, December 8, 2011
LEDComm: Bidirectional Communications using LEDs
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Filed Under:
LED,
microcontroller,
Radio,
Seminar Reports And PPTs
Saturday, December 3, 2011
FM Stereo Transmitter
2RDD2F7ZXD23
You'll find that this is a very easy project to build. It will transmit good quality sound in the FM band ( 88 - 108 mhz ). One inportant item is that the IC chip operates on 3 volts DC. The chip will get destroyed if it is operated on any voltage higher than 3.5 volts. The antenna can be a standard telescopic antenna or a 2 foot length of wire. The input is in the millivolt range and you may need to add additional pots for the inputs. I was able to use this circuit for a walkman and a portable CD player in my car. I used the headphone jack on both and varied the signal with the volume control.
To adjust the circuit tune your FM radio to a quite spot then adjust the trimmer capacitor C8 until you hear the signal that you are transmiting. When you have a strong signal adjust the resistor R4 until the stereo signal indicator lights. If the input is to high of a signal you may over drive the IC chip. Use two 15 turn pots on the input signals to bring the level down. You can balance the signal by using headphones. The inductor L1 is 3 turns of .5 mm wire on a 5 mm ferrite core.
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Filed Under:
Radio
Monday, November 21, 2011
AM FM Simultaneous Transmitter Using Digital IC
We are familiar with transmitters either working in AM or or in FM.But this circuit transmits both am and fm signal simultaneously at two different frequencies AM in 20 Mhz and FM in 100 Mhz.
The 5th harmonics of the fundamental is used to transmit the fm signal,hence it's range will be less than am signal One can also directly feed the audiosignal .Transistors Q1, Q2 forms the amplifier stage which is fed to the modulator formed by the nor gates .Use a long wire antenna for good reception
The 5th harmonics of the fundamental is used to transmit the fm signal,hence it's range will be less than am signal One can also directly feed the audiosignal .Transistors Q1, Q2 forms the amplifier stage which is fed to the modulator formed by the nor gates .Use a long wire antenna for good reception
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Filed Under:
Radio
Tuesday, July 12, 2011
Programmable Home Security Alarm System
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Filed Under:
microcontroller,
Radio
Thursday, January 13, 2011
Single Chip FM Transmitter
Description:
A simple FM transmitter links your home-entertainment system to a portable radio that can be carried around the house and into the back yard.For example,you can play music on the CD changer in your living room, and listen to it on a portable radio by the back-yard barbeque.IC1 is a voltage-controlled oscillator with integrated varactor.Its nominal frequency of oscillation is set by inductor L1 and a 390nH value places that frequency at 100MHz.Potentiometer R1 then lets you select a channel by tuning over the FM band of 88MHz to 108MHz.Output power is about -21dBm into 50 (most countries accept emissions below 10dBm in the FM band).
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Filed Under:
Radio
USB Mono FM Transmitter
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Filed Under:
Radio
Monday, January 10, 2011
How to build Simple Op-Amp Radio
This is basically a crystal radio with an audio amplifier which is fairly sensitive and receives several strong stations in the Los Angeles area with a minimal 15 foot antenna. Longer antennas will provide a stronger signal but the selectivity will be worse and strong stations may be heard in the background of weaker ones. Using a long wire antenna, the selectivity can be improved by connecting it to one of the taps on the coil instead of the junction of the capacitor and coil. Some connection to ground is required but I found that standing outside on a concrete slab and just allowing the long headphone leads to lay on the concrete was sufficient to listen to the local news station (KNX 1070). The inductor was wound with 200 turns of #28 enameled copper wire on a 7/8 diameter, 4 inch length of PVC pipe, which yields about 220 uH. The inductor was wound with taps every 20 turns so the diode and antenna connections could be selected for best results which turned out to be 60 turns from the antenna end for the diode. The diode should be a germanium (1N34A type) for best results, but silicon diodes will also work if the signal is strong enough. The carrier frequency is removed from the rectified signal at the cathode of the diode by the 300 pF cap and the audio frequency is passed by the 0.1uF capacitor to the non-inverting input of the first op-amp which functions as a high impedance buffer stage. The second op-amp stage increases the voltage level about 50 times and is DC coupled to the first through the 10K resistor. If the pairs of 100K and 1 Meg resistors are not close in value (1%) you may need to either use closer matched values or add a capacitor in series with the 10K resistor to keep the DC voltage at the transistor emitter between 3 and 6 volts. Another approach would be to reduce the overall gain with a smaller feedback resistor (470K). High impedance headphones will probably work best, but walkman stereo type headphones will also work. Circuit draws about 10 mA from a 9 volt source. Germanium diodes (1N34A) types are available from Radio Shack, #276-1123.
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Filed Under:
Radio
Sunday, November 14, 2010
How to build FM Telephone Bug
Here is a simple transmitter that when connected to a phone line, will transmit anything on that line (execpt the dial tone) to any FM radio. The frequency can be tuned from 88 to about 94Mhz and the range is about 200 feet. It is extremely easy to build and is therefore a good, useful beginner project.
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Filed Under:
Radio
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