wireless FM Transmitter

[Elven Commander]

Hi all,

I have been pondering this idea for a little now, and decieded to come and check out this site. When I got here, i saw that there was a related thread started and I have read that thread and searched around a bit. My aim is to make a project, and I would like to play mp3's that are playing on my computer, and play them in the other room.

My first question is, I read in the other thread that there are kits that do this, by using a PCI card. If I so wished it, is it possible to design and make my own PCI card for this ??? the other type I've heard/read about is where you plug it into the standard headphone jack. What is better??? I must make a digital project and thats all the specifications I have, right now i'm just idea surfing, and the idea of making my own board has always seemed cool.
If I did make my own PCI board, how hard is it to get the data thats being played on my computer to there??


I have made a FM transmitter in the past, a variable transmitter. Is there a range that a devise like this would normally follow. I was thinking mybe 88-90 mhz or something like that, but I wasn't sure if there was a prefered, or generally used range to go for. I'm not completely sure, but I was thinking that FM would be better then AM for a project like this. I know I wouldn't want a variable FM transmitter for the full FM spectrum (or so i think) would a device such as this have an option like a switch or what not, position 1 88.1 postion 2 88.5 position 3 88.9 etc??

If I were to make a project such as this, Basically you would take your signal from the computer, turn it into RF and then transmit it, and play it on the external recieving devise. From my understanding thats what I would have to do. Would i have to run it through an amp first?

Thank you for any input, i'm fairly new to electronics, and any help, comments or suggestions would be greatly appreciated.

Thank you for your time,

Elven Commander

p.s. I almost forgot, the BH1417F, Wireless Audio Link IC, I understand that this chip sends the data as a RF using FM, but I wasn't quite sure as to what "generating stereo composite signals" meant which is the 2nd function of this chip.

[Kevin Weddle]

Your talking a receiver transmitter for reproduction of an audio signal. It can be done but is bound to be inefficient should you choose to do it yourself. I don't even know of anything I could recommend. Although, sometimes things of this nature can work to a degree that you are satisfied with. AM is what I will explain. You need an oscillator that is fed to the emitter and a signal that is fed into the base. The resulting peak to peak is multiplied by the gain. A reproduction of both signals will be present. Not at all like addition. The receiver should amplify high gain, like a tunned opamp circuit, and consist of many stages. To tune an opamp, employ reactive elements wherever you can. In the gain, in the input, and in the output. Now you should be able to begin constructing a circuit.

[audioguru]

Hi Elvin,
You would need to make your own PCI sound card, complete with MP3 player and stereo FM transmitter. Since very few hobbiests make them and they make only one, I doubt that you can get the special PCI and MP3 decoder IC's without ordering 10,000 of them. You also must write a program for them if you can't get it from the internet. Or make them yourself from scratch using microprocessors, memory and gates.

The BH1417 transmitter project has already been shown. It has switches for up to 14 radio station FM frequencies, 7 at each end of the radio dial. It doesn't transmit data, it transmits composite stereo which is a mono L+R audio signal, a 19KHz stereo pilot tone and AM-modulated 38KHz suppressed-carrier L-R stereo sidebands.

People transmit stereo MP3 audio with the BH1417 project by plugging its inputs into the headphone jack on their sound card.

Hi Kevin,
Elvin is talking about making his own stereo FM transmitter using the BH1417 IC. He will receive stereo sound from it on an ordinary stereo FM radio. They are not inefficient, since many people build them from kits or the magazine project "Micromitter" that I posted on one of these forums. Never mind AM, it sounds lousy.