headphone jack to FM trannsmitter anyone?

[talon006]

i KNOW this exsists, but i cant find it, anyone know of a headphone jack to a radio transmitter (great for listeneing to your mp3 player in your car)

friend found it, then lost it, hes a jerk

anyone?

 

[audioguru]

Of course you can connect a jack to the input of an FM transmitter so an MP3 player can be connected.
You forgot to say if your transmitter is mono or stereo and fogot to show its schematic.

 

[dfhrace]

i would like to find/build an FM transmitter circuit schematic that can output stereo from an ipod any help would be great
thanx
dan

 

[audioguru]

You have the same subject posted all over this site, I just finished answering it.
Silicon Chip magazine published a good-quality stereo FM transmitter project. Kits are available. In Google, search for Silicon Chip Micromitter. The 1st link is their entire article for free.

Download and open the schematic:

 

[dfhrace]

wow thank alot i will be getting these parts tommow in school

 

[dfhrace]

yes well now the more i look at this how do i set the "station" in which it will produce and is there a link to the web site in which this is from or did you do this yourself?

 

[audioguru]

yes well now the more i look at this how do i set the "station" in which it will produce and is there a link to the web site in which this is from or did you do this yourself?

I told you how to find Silicon Chip's stereo FM transmitter project in Google. If you go directly to Silicon Chip's site then they will ask you to pay for the article.
In their article, they say how to set the switches of the frequency synthesizer for one of 4 station frequencies near the bottom of the band or one of 4 near the top.
I have seen a nice little product in the store made by Maxell, it has this circuit and sells for about $30.00CAN.

 

[mstechca]

I never seen a transmitter like that before.

Generally, to change the frequency, you will need to adjust the inductor and/or the capacitor.

I don't know which one to change on Audioguru's diagram.

There is a well known equation to find the (resonant) frequency based on the two components I mentioned. Do a google search and you should be able to find it.

 

[audioguru]

I never seen a transmitter like that before.

Generally, to change the frequency, you will need to adjust the inductor and/or the capacitor.

The circuit has a coil L1 with a 22pF cap across it. Then it has a varactor diode VC1 across them for tuning the RF frequency. The IC uses a 7.6MHz crystal oscillator in a frequency synthesizer circuit with a counter and a Phase-Locked-Loop circuits. The switches select a counter ratio which determines a very accurate RF frequency. The PLL sets its voltage for the varactor diode's tuning capacitance.
The crystal oscillator is also divided down for the accurate 19kHz and 38Khz stereo frequencies.

Most RF stuff today use a frequency synthesizer.

 

[evoke]

but can you build one that the power works of the power of the ipod. do you need some special jack for it. i found a powerless AM transmitter circuit. if you talk in to the speaker it will oscillate the crystal and power the circuit to transmit a sound on a AM band.

here is the schematic i found
**broken link removed**

i was thinking if you replaced the speaker with the headphone jack which you would plug into your ipod, that it could power the circuit and transmit the sound coming out of the MP3 player.

i know it would only go only a few meters but that is all i want.

anybody see a flaw in this idea.

thanks for any replys

 

[evoke]

powerless AM transmitter

but can you build one that the power works of the power of the ipod. do you need some special jack for it. i found a powerless AM transmitter circuit. if you talk in to the speaker it will oscillate the crystal and power the circuit to transmit a sound on a AM band.

here is the schematic i found
**broken link removed**

i was thinking if you replaced the speaker with the headphone jack which you would plug into your ipod, that it could power the circuit and transmit the sound coming out of the MP3 player.

i know it would only go only a few meters but that is all i want.

anybody see a flaw in this idea.

i was thinking of doing this for an FM transmitter but you eould need more power. i have only a mp3 player that runs off 1.5 Volts

 

[audioguru]

How are you going to make your ipod SCREAM every couple of seconds to power the transmitter?
Do you like lousy-sounding mono AM radio?
You won't find an FM stereo transmitter circuit that works from only 1.5V. Don't forget that a 1.5V battery quickly drops to only 1.0V.

 

[Madhouse]

A quick scan of flea-bay will source you an ipod compatible fm transmitter that works off a single AA cell. I've got one at home - works a treat for about 20 metres and an hour or so!