Showing posts with label fm. Show all posts
Showing posts with label fm. Show all posts
Saturday, September 20, 2014
88 108 MHz FM Broadcast Transmitter
This circuit will transmit a continuous tone audio FM broadcast band (88-108 MHz) which could be used for remote control or security. Circuit draws about 30 mA with a 6.9-volt battery and can receive about 100 meters. A 555 timer is used to produce the tone (about 600 Hz), which modulates the frequency of a Hartley oscillator. A second JFET transistor buffer stage is used to isolate the oscillator from the antenna to the antenna position and length has less effect on the frequency.
Fine adjustment can often be done by adjusting the 200 Ohm resistor in series with the battery. Oscillator frequency is set by an inducer of turn 5 and 13 pF capacitor operated. The inductor is wound around a # 8 x 32 bolt (about 3 / 16 in diameter) and then removed by unscrewing the screw. The inductor was then streached to about a length of 3 / 8 inches and hit near the center. The oscillator frequency should come out somewhere near the center of the band (98 MHz) and can be moved up or down slightly the expansion or compression of the coil.
A small signal diode (1N914 or 1N4148) is used as a varactor diode so that the total capacity in parallel with the coil varies slightly in the type of audio causing the oscillator frequency to change the audio rate (600 Hz) . The ramp waveform at pins 2 and 6 of timer applies to the reverse diode across a large bias (1 Meg) resistor so that the capacity of the diode changes as voltage changes thus increasing altering the frequency of tank circuit.
Alternatively, an audio signal could be applied to the 1 Meg resistor to modulate the oscillator but may require a pull-up resistor to reverse bias additional diode. The N channel JFET transistors used should be high frequency VHF or UHF types (Radio Shack # 276-2062 MPF102) or similar.
Fine adjustment can often be done by adjusting the 200 Ohm resistor in series with the battery. Oscillator frequency is set by an inducer of turn 5 and 13 pF capacitor operated. The inductor is wound around a # 8 x 32 bolt (about 3 / 16 in diameter) and then removed by unscrewing the screw. The inductor was then streached to about a length of 3 / 8 inches and hit near the center. The oscillator frequency should come out somewhere near the center of the band (98 MHz) and can be moved up or down slightly the expansion or compression of the coil.
A small signal diode (1N914 or 1N4148) is used as a varactor diode so that the total capacity in parallel with the coil varies slightly in the type of audio causing the oscillator frequency to change the audio rate (600 Hz) . The ramp waveform at pins 2 and 6 of timer applies to the reverse diode across a large bias (1 Meg) resistor so that the capacity of the diode changes as voltage changes thus increasing altering the frequency of tank circuit.
Alternatively, an audio signal could be applied to the 1 Meg resistor to modulate the oscillator but may require a pull-up resistor to reverse bias additional diode. The N channel JFET transistors used should be high frequency VHF or UHF types (Radio Shack # 276-2062 MPF102) or similar.
Wednesday, September 17, 2014
Simple Fm circuit Wiring diagram
I think most of people like to make radio diagram.Because most of them like to listen radio programs from the radio which they made by their own hands.You all know Free schema Diagrams 4U is a website which is giving simple schema diagrams.So that most of beginners can start their electronic life simply.So today Im going to give you a very simple schema diagram. Here we have used common electronic parts.this schema can be operated with 3V power supply
Note:
# Build this on a pcb
# Build this schema in a small area
# Dont supply over 3V
Read More..
Note:
# Build this on a pcb
# Build this schema in a small area
# Dont supply over 3V
Sunday, September 14, 2014
Simple FM transmitter with 2N3904
In this section discuss about the series of mini fm transmitter, with broadcast coverage of about 300-400 meters. when using a 9 volt working voltage, the transmit power of about 300 meters and when using the working voltage 12 volts, the range of about 400-450 meters, depending on the antenna you use.
This scheme of simple fm transmitter
For L1 and L2 windings 5 times the wrap, you can use a pen to fill melilitnya so neat and after lepaslah content of these pens. C5 is used for placement of broadcasting frequencies, can be tuned between 88-108 mhz, to reach further use steering antenna or Yagi antenna.
Part List
C1 = 0.001uF
C2 = 5.6pF
C3 = 10uFC4 = 10uF
C5 = 3 - 18pF Adjustable capacitor
R1 = 270R
R2 = 4.7K
R3 = 10K
R4 = 100K
R5 = 4.7K
R6 = 4.7K
Q1 = 2N2222A
Q2 = 2N3904
L1 = 5 turn
L2 = 5 turn
Tuesday, September 9, 2014
Spy FM Transmitter circuit
This is so impotent schema for us,Because we can use this schema as a spy unit.This schema can transmit signals about 30m.And the other important thing is the power of this schema we can operate this schema with 1.5v to 3v(1.8 mA at 1.5 Volts )
Note
# If you are unable to find the transistor here use these transistors Because here you can use equal transistors such as 2N2222A, BFxxx series, BC109B, C, and even well known BC238.
# Use 1.5v to 3v for this schema.Dont supply more than 3v(3v can cover the max range 30m)
Thursday, September 4, 2014
Filter freq dirty from an fm transmitter
Low pass filter is a circuit to filter freq dirty from an fm transmitter. so we get a clean signal. and can maximize the output power generated from the booster. low pass filter is capable to 150 watts. in this post . file [lay] that can only be opened with software sprint layout. for those interested please download here.
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