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Need Help on FM Trans.

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Basem

New Member
i want to make FM Trans. Circuit ...





But:
1- I can't find Q1 ZTX108
2- VC1 5-60pF ... i find 4-40pF : can i use it or not ??
3- Can i Check my Result before received signal on Radio Device ??
 

audioguru

Well-Known Member
Most Helpful Member
Any modern little NPN transistor will work as the oscillator. I used a 2N3904 in my FM transmitter.
You don't show where you are so if you are in Europe then you can use a BC547 transistor.
The tuning capacitor will work but the coil might need 1 0r 2 more turns.
Make it and try it. A simulation won't be useful.

It is a very simple circuit with horrible performance:
1) Its antenna is connected to the tuned circuit so the frequency will change if something moves toward or away from the antenna.
2) It doesn't have a voltage regulator so its frequency will change as the battery voltage runs down.
3) It will sound awfully muffled because it doesn't have pre-emphasis like all FM radio stations have and the de-emphasis in all FM radios will cut its high audio frequencies.

It doesn't need two opamps because the second opamp can be replaced with a piece of wire.
It must be made on a pcb or on stripboard with all the traces and wires cut as short as is possible. It won't work if you make it on a breadboard.
 

Basem

New Member
I get L1 is 0.112uH ... i can't make coil with my hand :( .. so i can't increase more Turns ..

Q: i Can't sent any voice through this circuit ??? can you help me with circuit that able me to transmit voice ??
Or Help me how can Modify this Circuit ... ?

- thank you for Ur important notes ... it's very useful to me
 

Ziddik

Member
u can make a coil by winding about 5 turns at a diameter of 3.5mm. Get an ink tube from an ordinary pen and wrap 5 turns on it with an insulated copper wire being careful not bend it. Remove th coil u made n remove the insulation from both end of the coil n solder it on the board n U HAVE DONE!! I have made a really useful transmitter using bc547!! U can even use bc549,bc548.etc mail me if u need any help -GOODLUCK.
Ziddik -karathoor-tirur-kerala-india]
 

mathewkyle

New Member
Dear All,

Thanks for the great work.

I am interested in doing a project in wireless communication. Please provide ideas on antenna design, software designed radios, smart antennas, propagation models, etc. Anything will help in wireless communication will suffice.

Thanks
 
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