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help FM TRANSMITTER (by colin mitchel)

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bond000

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i like to use 9v battery for this circuit for compactness. what changes should i make. if i use a 1/4 wave antenna,can i get 600 meters range? or could some one tell me how to make a coil loaded antenna for this circuit?can i substitute 2N918/2n3866 for the third transistor, for increased range? please help.
 

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colin55

Well-Known Member
This circuit will be best on 6v. Any higher voltage will be wasteful as the transistors cannot deliver any more output.
Using a 2N3866 is just going to take a much higher current for very little extra range. Use the half-wave antenna for a range of approx 600 metres.
 
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bond000

New Member
thank you Mr.colin! lucky to have you here. but, i want to use it as a bug. but,for 6v i have to use 4 AAA and a battery holder.kind of bulky.isn't it?if i use 9v battery will there be any problem except for the power wastage? what will be RF output in mW,if i use a 9v battery. or please tell me what will be the signal strength(roughly) in µv measured at 3meters.
i want to make the circuit using surface mount components and place it on top of a 9v battery. like voyager. the oscillator circuit and audio stage of the above circuit is identical to voyager. except for the microphone gain resistor and buffer stage.isn't it? and you used 9v there.could you explain on this?
thank you once again.
 
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audioguru

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Most Helpful Member
An FM preamp will simply be overloaded by all the local FM radio stations and lower frequency local TV stations.
 
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