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Simple FM transmitter
- Thread starter ElectroMaster
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Not sure about this one, but silicon chip did one of a similar design that was sold in a kit form at one of the local electronic kit retailers here in Aust. I think it was in their Nov 89 issue. It ran off 2 X 1.5V batteries, and the output coil was actually etched into the PCB rather than wound. It got a range of about 100m from memory, and fitted into a match box, complete with batteries.
I hooked one up to a 9V battery, and it was good for 500m, and that's only the point at which I turned the car around and went home again.
I hooked one up to a 9V battery, and it was good for 500m, and that's only the point at which I turned the car around and went home again.
Not sure about this one, but silicon chip did one of a similar design that was sold in a kit form at one of the local electronic kit retailers here in Aust. I think it was in their Nov 89 issue. It ran off 2 X 1.5V batteries, and the output coil was actually etched into the PCB rather than wound. It got a range of about 100m from memory, and fitted into a match box, complete with batteries.
I hooked one up to a 9V battery, and it was good for 500m, and that's only the point at which I turned the car around and went home again.
I hooked one up to a 9V battery, and it was good for 500m, and that's only the point at which I turned the car around and went home again.
If you wanted Stereo, perhaps Micromitter of silicon chip is the best and One "AN920" has suggested specific mods for improving unwanted Noisy tone comming at higher end of audio. you may implement that. Once you want Mono, i feel MOD4 is superior by any means.
Ramsey Electronics sells a FM Transmitter kit with an external antenna connector to create a greater spread.
Ramsey Electronics
However, it's a battery hog with an external coupler
Ramsey Electronics
However, it's a battery hog with an external coupler
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.
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.
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.
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.
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"
(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.
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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