stereo Transmitter

[audioguru2]

An FM transmitter needs a mono audio signal or a composite stereo signal for an input.
A mono audio signal can be from a microphone and most FM transmitter circuits have enough gain for a microphone.
Stereo inputs to the stereo encoder can be from a CD player or an MP3 player.

The stereo encoder should have pre-emphasis and sharp lowpass filters. It must have an accurate crystal oscillator.
The FM transmitter will have excellent frequency stability if it uses a Phase-Locked-Loop circuit that has a crystal oscillator as its reference. For good stereo, the audio frequency response of the FM transmitter must be flat to 53kHz.

 

[MNA]

And what about renaud stereocoder.....it uses lot of parts but what u r telling about the encoders ....I think for good results ,the crkt might become complicated?  ....

222_stereo_enc.zip

 

[MNA]

the link to previous crkt http://web.telia.com/~u85920178/  in projects section,fm transmitters,xtal wbfm tx

 

[audioguru2]

Harry's 222 stereo coder is very crude like he says. It does not have enough pre-emphasis and has no filtering whatsoever. Without filtering, harmonics of audio will heterodyne with the 19kHz pilot and with the lower 38kHz sideband frequencies and create whistles in the sound. His choice of an LM358 opamp is poor because it has difficulty operating above 5kHz and has crossover distortion.

Harry's crystal FM transmitter might be good. It uses a Plessey IC that might be difficult to purchase.