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Simple FM transmitter

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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" of twisted wire, stop and cut the looped end off, leaving about 1/2" of twisted wire (this forms the capacitor) and 1/2" of untwisted wire for leads.

 
#2
could you transmit a stereo coded signal with this circut?
connect it instead of the mic...
 

audioguru

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#3
C4 in the project has such a high value of 0.1uF that it cuts frequencies above only 1.2KHz. FM stereo needs a response that is flat at 53KHz.
 
#13
need a Circuit for Finding out a hidden RF transmitter

Hello to every one,

I need a Circuit for Finding out a hidden RF transmitter. Can some one sugges me any idea please ?
A RF Transmitter of a fixed Frequency will be hidden some where around, And I'am Supposed to find the transmitter. This is a project competition held here. Please Help.

Thank U

i'm new here and am not able to creat a new thread !!!
 

mvs sarma

Well-Known Member
#14
This circuit is a simple two transistor (2N2222) FM transmitter. .........When you have about 1" of twisted wire, stop and cut the looped end off, leaving about 1/2" of twisted wire (this forms the capacitor) and 1/2" of untwisted wire for leads.

I really hope that ElectroMaster would have seen the Mod4 of Audioguru. That that was a fine mod to optimize the entire design. I am yet to understand the idea behind old schematic being put forth again.

This is not to offend the owner of the site please.
 
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Nigel Goodwin

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#15
I really hope that ElectroMaster would have seen the Mod4 of Audioguru. That that was a fine mod to optimize the entire design. I am yet to understand the idea behind old schematic being put forth again.
Perhaps you might try reading the dates on the posts?, the only person "putting it forth again" is YOU! - the original is six years old.
 

mvs sarma

Well-Known Member
#16
Perhaps you might try reading the dates on the posts?, the only person "putting it forth again" is YOU! - the original is six years old.
Yes Nigel, it was a blunder, that i didn't note the date of the post. Sorry for that.
BTW how it appears as a post and with an overall of 12 posts above it afresh Sir? It was an item with 11 or 12 replies over that at the time I saw it .
 

Nigel Goodwin

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#17
Yes Nigel, it was a blunder, that i didn't note the date of the post. Sorry for that.
BTW how it appears as a post and with an overall of 12 posts above it afresh Sir? It was an item with 11 or 12 replies over that at the time I saw it .
It re-appeared because someone (firoz3321) posted a reply in the thread.
 

audioguru

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Most Helpful Member
#20
could this be used to magnify the signal of my ipod's fm tuner? it cuts out at times.
This thread talks about an FM transmitter.
You have a receiver problem that should be in its own thread.

Phone your radio station and ask them to boost their power so that your cheap or defective radio can pick them up without cutting out. Good luck.
 
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