Help in making FM transmitter

Thread Starter

Chaitanya_om

Joined Sep 11, 2010
1
Hello everyone, I m making FM transmitter.Circuit diagram is shown in attachment.
I m building it on bread board.One time it work perfectly after it is not working i also check transistors.I add var cap in parallel with inductor for tuning,i can also receive it on my receiver but i herd pulses may be from oscillator.
When i disconnect amplifier (T1) from T2 i get perfect frequency but after applying AF to base it is't work plz help.
 

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Wendy

Joined Mar 24, 2008
23,415
How long have you had it? It does sound like something died or went out. I'd be suspicious of the electrolytic caps. If they shorted they would connect the stages. Measured any voltages?
 

Audioguru

Joined Dec 20, 2007
11,248
A circuit built on a breadboard might work up to 1MHz. This project works at 100MHz which is much too high for the very high stray inductance and stray capacitance of a breadboard. Simply moving one of its many long wires would change its frequency a lot.
Use a compact pcb or stripboard with all tracks cut short.
 

PRS

Joined Aug 24, 2008
989
Audioguru is right. Don't use a breadboard. Build your circuit on a copper-clad board using short paths for high frequency signals.
 
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