Someone Electro
New Member
I want a simple FM transmiter but all i found had a electret microphone and i want to input from my computers sound card.
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audioguru said:The simple FM transmitter is too simple:
1) Its tuned circuit is connected directly to the antenna. So if anything gets near it then its frequency will change.
2) It doesn't have a voltage regulator. Then its frequency will also change as its battery voltage runs down.
3) Its input sensitivity is about 5mV. The output from your sound card is much too high and an attenuator is needed.
4) It doesn't have pre-emphasis (treble boost) like FM radio stations have so it will sound very muffled (without treble audio frequencies) when heard on an FM radio.
5) It has a very weak output power and might not have a range to across the street.
audioguru said:My FM transmitter has an RF amplifier transistor to isolate the antenna from the oscillator's tuned circuit.
It has pre-emphasis so it sounds crisp and clear.
It has a low dropout voltage regulator so its frequency doesn't change as the battery voltage runs down.
But it is not simple and it is not stereo.
audioguru said:I think my FM transmitter has an output power of about 220mW but others say it is only 20mW.
It draws 53mA from a new 9V alkaline battery.