It is illegal to operate an uncertified TV transmitter.

It is illegal to operate a certified TV transmitter without a licence.

In the USA this month, analog TV transmissions from TV stations will cease.

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Uncle $crooge

 

Actually, they moved the transition from analog to digital to between March 14 and June 12.

I guess not enough people got a government coupon or something.

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Mike2545

 

what's if I changed the inductor from which the antena rises changed in length could this affect the frequency.
THANKS
MEDSOL

 

Guess what determines the frequency of the very simple FM oscillator?
1) The length, diameter, turns spacing, wire size and number of turns of the coil.
2) The inductance of the traces of the circuit board layout.
3) The capacitance of the trimmer capacitor, the capacitance of C6, and the capacitance of the transistor.
4) The supply voltage (because it affects the capacitance of the transistor).
5) The capacitance of the circuit board layout.
6) The distance to the antenna of anything conductive that affects the capacitance of the tuned circuit.
7) The distance of anything conductive near the circuit board.
8) Maybe more things that I forgot about.

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Uncle $crooge

 

very nice
many thanks

 

hello
could u plz help me to understand this cct
i am realy have a great problems in dealing with cct for coomunications
could you also estimate the range (distance) for this cct

 

hello
could you plz help me to understand this cct
i have a realy great problem in dealing with communication cct.s
could u alsi estimate the range ( in distance) for this cct and how

 

The very simple circuit uses an audio preamp transistor and an RF oscillator transistor.
Its output power is low so that buildings, trees and hills block its signal.
Its range might be 500m in the open to a very sensitive home stereo FM tuner or car radio, about 150m to a cheap Sony Walkman portable radio and across the street to a cheap "scanning" radio from The Dollar Store.
Its range decreases as the battery runs down.

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Uncle $crooge

 

I cant still post threads so im posting this here........I built a fm transmitter.....the circuit says it goes up to 400m...well i get a very clear "triiiiiiiiiiiiiiiii" sound from the radio when i connect it to the power supply...its definetely working but when i speak from my mike there is no sound.I used a mike i got a from a very old telephone. The circuit says to use an electret one. Is this affecting my transmitter???...other wise it has got a good range..i can get that sound for about 30m (still didnt check properly) Also i want to build a good antenna for this ...pls help me
(here's the link : ="http://www.uoguelph.ca/~antoon/circ/fmt1.htm"

 

That is the poorly designed circuit that I fixed then I improved it.
Of course it needs an electret microphone. You don't even know which type of microphone you have.
The transmitter's audio preamp transistor is not biased properly so it is saturated when the 9V battery is brand new and it is cutoff when the battery is used a little.

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Uncle $crooge

 

I fixed a electret microphone to it but there seems to be no sound when i speak. is there something wrong with the circuit diagram or something wrong with my circuit....???

 

It is a terrible circuit.
Its preamp transistor is not biased correctly so might be saturated or cutoff which makes it not work.
Its radio frequency could be anywhere and might not be in the FM broadcast band.

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Uncle $crooge

 

can i use an 100nH axial inductor instead of an air coil for the LC tank?

 

I never tried one and I didn't measure the inductance of my simple air coils but they work.

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Uncle $crooge

 

[QUOTE=ElectroMaster;66]This circuit is a simple two transistor (2N2222) FM transmitter. No license is required for this transmitter according to FCC regulations regarding wireless microphones. If powered by a 9 volt battery and used with an antenna no longer than 12 inches, the transmitter will be within the FCC limits. The microphone is amplified by Q1. Q2, C5, and L1 form an oscillator that operates in the 80 to 130 MHz range. The oscillator is voltage controlled, so it is modulated by the audio signal that is applied to the base of Q2. R6 limits the input to the RF section, and it's value can be adjusted as necessary to limit the volume of the input. L1 and C6 can be made with wire and a pencil. The inductor (L1) is made by winding two pieces of 24 gauge insulated wire, laid side by side, around a pencil six times. Remove the coil you have formed and unscrew the two coils apart from each other. One of these coils (the better looking of the two) will be used in the tank circuit, and the other can be used in the next one you build. The antenna (24 gauge wire) should be soldered to the coil you made, about 2 turns up from the bottom, on the transistor side, and should be 8-12 inches long. To make C6, take a 4 inch piece of 24 gauge insulated wire, bend it over double and, beginning 1/2" from the open end, twist the wire as if you were forming a rope. When

you have about 1"