Hi friends i have created one fm radio transmitter with four stages which will give out a power about 1W and the range is also good.is there any possibility to assemble or connect anything else to my system to make it useful as any other. i mean any new modification can be made like making it as work as a radar or something like that or can we improve the gain of the system or any sort of filters can be fitted etc. please reply. i have taken the circuit from this link http://electronicsforu.com/electronicsforu/lab/freecircuitslist.asp?id=464&title=Four-Stage%20FM%20Transmitter
The very old circuit will sound bad. Also it is mono, not stereo like modern FM transmitters.
All FM radio stations have pre-emphasis which is a boost to high audio frequencies. Then all FM radios have the opposite called de-emphasis which is a reduction of high audio frequencies which also reduces hiss but then the audio sounds perfect. So since this old circuit does not have pre-emphasis then its signal will have high audio frequencies reduced when heard on an FM radio.
It is illegal in most countries to transmit with such a high power. In most countries there are very many FM radio stations so this powerful transmitter will probably be used on the same frequency as a real radio station which will cause severe interference.
Can you please provide me with any good quality fm transmitter circuit.we have to submit it for our college.i believe you can provide it for me,if any type of micro controller is there it may be much helpful.Thank you
Many common parts in The West are not available in your country. Why don't you ask on a website in your country?
In Google, look for The Micromitter. It was a project published by Silicon Chip magazine in Australia about 6 years ago for an FM stereo transmitter with pretty good performance. A kit is available in Australia and New Zealand. It uses one of the Rohm chips that are used in most MP3 player to FM car radio adapters available everywhere.
I have the schematic of the Micromitter but I won't post it here because you probably cannot obtain its IC.
Why do you talk about a microcontroller? It is not used in an FM transmitter.
i just mentioned about micro controller because if in any way can we stabilize the frequency,i mean not much change from that of the original frequency that we are generating. seen some circuits with PLL along with some PIC uC.
The modern FM transmitter ICs use a very accurate crystal oscillator in a phase-locked-loop frequency synthesizer circuit. They select the frequency with DIP switches on some ICs or with digital logic bits (from a microcontroller)on other ICs.
Rohm has been making these ICs for at least 6 years. Why doesn't your teacher teach you about them?
hi, i made the old circuit and which type of antenna should i use to get the maximum range.Can i use Yagi(but i know it is for UHF)? How could i measure the power output from the circuit? please help
The sensitivity of your FM radio is very important to the range. Using a balun RF transformer feeding a directional Yagi antenna on both the transmitter and radio will increase the range. Of course nothing must be in between.
hi the frequency is not at all stable,can you suggest any method to create the 88Mhz-108Mhz signal with crystal or something.If possible give me the circuit to generate the VHF with available crystals.
You made the very old poor quality circuit that has an unstable frequency. I was talking about new FM stero transmitter circuits that use a crystal oscillator and a phase-locked-loop frequency synthesizer.
It is up to you if you want a quality FM stereo transmitter.
The old BA1404 transmitter IC had such poor performance that Rohm discontinued making it about 6 years ago and replaced it with the much better ICs. Read about it in Google.
FM TRANMITTER
Posted - Feb 07 2011 : 12:31:22 PM
