Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
I want to make a 20 or 30 meter range FM transmitter which i want to connect to my TV so that i can listen the audio in my phone. I am looking for something simple which has good quality mono audio transmission.
What frequency range? Additionally I assume you want to connect the audio out (maybe line audio) from the TV and listen to it on what? Phone to me implies telephone? Maybe you mean an FM receiver with headphones?
The guy here in the forums who is good with things like this is AudioGuru who could likely suggest a good circuit. The problem with most circuits like this is parts placement and environment. The majority of these little transmitters drift frequency with temperature, humidity and other variables.
What frequency range? Additionally I assume you want to connect the audio out (maybe line audio) from the TV and listen to it on what? Phone to me implies telephone? Maybe you mean an FM receiver with headphones?
The guy here in the forums who is good with things like this is AudioGuru who could likely suggest a good circuit. The problem with most circuits like this is parts placement and environment. The majority of these little transmitters drift frequency with temperature, humidity and other variables.
Hi Ron.
i will listen the "audio out" of my TV in my mobile phone(nokia,samsung, etc) FM radio, these days all mobile phone has FM radio built into it. little variation in frequency etc shouldnt be an issue. I will power the transmitter using a regulated DC power supply.
Simple FM transmitters work very poorly:
1) Their radio frequency changes when something moves toward or away from the antenna.
2) Their radio frequency changes when the supply voltage changes so a voltage regulator is needed.
3) Their radio frequency changes when the temperature changes.
4) They do not have pre-emphasis (treble boost) like all FM radio stations so the de-emphasis (treble and hiss cut) in all FM radios reduces high frequencies and makes muffled sound.
Silicon Chip magazine in Australia had an FM stereo transmitter project (The Micromitter) about 7 years ago that uses a modern Rohm IC with a crystal controlled frequency synthesizer with phase-locked-loop. The same line of ICs is used in MP3 to car radio FM transmitter products available.
Simple FM transmitters work very poorly:
1) Their radio frequency changes when something moves toward or away from the antenna.
2) Their radio frequency changes when the supply voltage changes so a voltage regulator is needed.
3) Their radio frequency changes when the temperature changes.
4) They do not have pre-emphasis (treble boost) like all FM radio stations so the de-emphasis (treble and hiss cut) in all FM radios reduces high frequencies and makes muffled sound.
Silicon Chip magazine in Australia had an FM stereo transmitter project (The Micromitter) about 7 years ago that uses a modern Rohm IC with a crystal controlled frequency synthesizer with phase-locked-loop. The same line of ICs is used in MP3 to car radio FM transmitter products available.
Rohm do not make FM stereo transmitter ICs anymore.
They are not available today at the two largest American parts distributors.
There is (was?) a kit for The Micromitter is Australia and New Zealand.
Hi..
I made the following fm transmitter but it didnt work. The reason for this circuit not working is probably because the fet BF246 was not available so the shop keeper gave me another alternative part which he told me should work. when i power my circuit from my pc my pc shuts down seems like there is a short in the circuit. View attachment 62877
So i gave it up and looking for a new better transmitter.
Audioguru I found the following circuit diagram let know how they will work out.
The FM transmitter with two BF199 transistors is pretty good and can also use 2N3904 or 2N2222 transistors instead. Use a short antenna length to reduce the range to what you need.
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