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The pre-emphasis provided by R1 and C2 is cancelled by the lowpass filter of R2 and C4 and C5.zlatkoMM said:If you want simple FM transmitter try this one:
zlatkoMM said:If you want simple FM transmitter try this one:
Audioguru said:zlatkoMM said:If you want simple FM transmitter try this one:
The values are for the 50us equalization used in Europe, Australia and New Zealand.
ajex said:The IF transformers in FM radios have a ferrite core and work at only 10.7MHz.zlatkoMM said:how make L2 coil? can we use IF ferrite core (in FM radio)for making this coil.
But the tuning coils in FM radios have air cores so that they can work at 100MHz.
can you tell me what is the distance that we can use to transmit.[/b]
These simple circuits do not have much power. FM radios have a wide selection of quality from cheap ones that might pickup a simple FM transmitter across the street to hi-fi and car radios that are extremely sensitive and can pickup a simple FM transmitter that is 2km (nothing in between) away.
My fairly low power FM transmitter has a range over a huge river valley of 2km.
America started broadcasting FM first. They boost the high audio frequencies (pre-emphasis) then the radio cuts the high audio frequencies (de-emphasis) so that the audio is perfect but hiss from the radio transmission is reduced. It is 75us."The values are for the 50us equalization used in Europe, Australia and New Zealand."
what is the mean of this, please explain it simply..
thanks..
It was a very long time ago when the high audio frequencies were fairly low level because microphones and recorders were poor.
Europe began broacasting FM later when microphones and recorders were better and they discovered that high audio frequencies were boosted too much by the Americans so they reduced the amount of boost to 50us. Australia and new Zealand made the same change as Europe.
So American and European radios have different EQs. But many simple FM transmitter circuits do not have any pre-emphasis so the de-emphasis circuit is all FM radios causes their sound to be muffled.
The IF transformers in FM radios have a ferrite core and work at only 10.7MHz.
But the tuning coils in FM radios have air cores so that they can work at 100MHz.
Audioguru said:There are hundreds of FM transmitter projects on the internet. All of them use RF coils that have air cores. Just 5 turns to 9 turns is all they are.
Why do you want to be different and then maybe your circuit won't work?
Audioguru said:I built my FM transmitter on a compact Veroboard layout with air-core coils and it works perfectly. Yours won't work if L1 has a ferrite core. Only the RF choke L2 uses a ferrite core.
Dont remove C4 - use better 470pF2) Remove R2 and C4.
3) Change C5 to 330pF.
It has exactly the same oscillator circuit as mine. Except it has an emitter bypass capacitor. It is also modulated exactly the same as mine producing AM and FM.zlatkoMM said:Look carefully how is designed oscilator part!
One advantage of using TX200 instead Audioguru design is better oscilator.
This way enable much stable output frequency deviation then Audioguru
design( im not 100% sure).
But it sounds bad because its pre-emphasis (treble frequencies boost) is cancelled by the lowpass filter of R2, C4 and C5.Then design of TX200 is much simple then AudioG design.
The base of the transistor needs a small capacitance to ground so that the oscillator works as a common-base circuit. C5 couples the base to ground. C4 is not needed.Dont remove C4 - use better 470pF
Then all the high audio frequencies will be gone.Change C5 to 10nF
nalinda.com said:Hi ajex
From where did you find the transistor. Im from Sri lanka too.
thz vry much..zlatkoMM said:You can build this very frequency stable FM transmiter: