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karthikeid

Fm transmitter

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I should can this response.

That circuit has, no RF buffer amplifier, so the frequency will drift if objects are placed near the antenna, no voltage regulator, so the frequency will change as the battery runs down and no pre-emphasis so it will sound like an AM radio.

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hi

i have made this circuit
http://w1.859.telia.com/~u85920178/tx/bug5.htm

at one frequency it is working fine for a long distance but when i speak there is bzz noise nd not able to hear clearly, can u help me to overcome this problem ??? 
in this circuit i have used 10pf instead of 12pf....

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Why did you ask for a circuit that works, if you were only going to build a different one that doesn't work?

I could be many things.

Are you powering it from a mains adaptor? The internal capacitor might not be large enough so add a 1000

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The electret mic must be connected with the correct polarity. Its metal case has the wire that should be connected to the circuit's ground.
The mic must be connected with very short wires or with a shielded audio cable.

You must not touch any part of the circuit when it is transmitting to avoid hum pickup from your hands.

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hi

http://rapidshare.com/files/276652026/fm_transmitter.pdf.html

check this circuit need some help building this one... ;D

Please attach your schematic here instead of over at RapidShare.

The very old circuit will sound bad and have its frequency change when its supply voltage changes.
I don't know where you will find a clip-on heatsink for the output transistor.

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500m through what? Free space, a forest or town?

What receiver are you using? A cheap Chinese FM radio won't be able to pick it up from as far away as well as a state of the art car radio.

What aerial are you useing? A high gain yagi array will transmit/receive the signal from a long away but will be more directional, a simple monopole will not transmit/recieve the very var but will pickup/send the signal in all directions.

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My FM transmtter has a range of more than 2km to my extremely sensitive home stereo and car radio.
Its range is 300m to my cheap Sony Walkman radio.
Its range is 100m to a cheap clock radio.
Its range is across the street to a cheap scanning radio from The Dollar Store.

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hi

some of the components are not presently available to me to build that circuit...

but i have attached one more file can u provide me some suggestions on it... 

i am not able to attach the file here saying the dir is not writable here...
so i have uploaded in rapidshare sorry for the inconvince.
http://rapidshare.com/files/277282868/transmisso__fm.gif.html

in this circuit 0.3uH is given how to wind the coil ???

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Which components can't you get hold of?

It's possible to substitute some of the components.

Rapidshare has limited downloads per day unless you pay, for images use www.tinypic.com which has limitless sownloads.

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I told you about the problems with that circuit before.

You haven't even answered my question.

I give up, you're on your own, as you don't seem to want to help yourself, I don't see why I should help you.

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The simple FM transmitter circuit has its tuned circuit connected to its antenna which causes its frequency to change if something moves near the antenna.
It does not have a voltage regulator so its frequency also changes as the battery voltage runs down.
It does not have pre-emphasis like all FM radio stations have so it will sound muffled like your stereo with its treble tone control turned all the way down.

The LM2931 is a 5V low-dropout regulator. All semiconductor manufacturers make some.
The 78L05 fails when the battery voltage is less than 7V. A 5V low dropout regulator still works perfectly when the battery voltage has dropped to 5.5V.

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hi

ok chill hero999...
why i am asking is that i have those components with me so that is why i was asking about that circuit....kindly help me out to do this circuit....
i cant get LM2931A...is there any substitute ???

you get LM1117-5

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