Re: need help asa

[ungastm]

audio guru how am i able to find the right frequency?
how to test if my device is working?

 

[audioguru2]

audio guru how am i able to find the right frequency?
how to test if my device is working?

Turn the trimmer capacitor with a plastic screwdriver with an FM radio tuned to the middle of the FM band near the transmitter. You will hear acoustical feedback howling when it is tuned to the radio's frequency.

I have a cheap Sony Walkman FM radio that is overloaded by my FM transmitter and the signal is all over its dial. It has a local/distant attenuator switch and it receives my transmitter properly only when it is set to Local.

 

[ungastm]

which of the two trimmer will i tune?or both will be turned?
i will set the frequency of the fm radio in the middle?

 

[audioguru2]

The trimmer capacitor in the oscillator circuit tunes the transmitter's frequency.

The trimmer capacitor at the output RF amplifier is tuned for a peak at 100MHz (the farthest range). When it is peaked at 100MHz (the middle) then the transmitter still works pretty good at 88MHz and at 108MHz and in between.

First try it with the radio tuned to 100MHz (the middle) because the stray capacitance from the layout of your circuit might cause the tuning of the transmitter not to reach one end of the dial.

 

[ungastm]

does this means that it works in the three channel at the same time?
at 88,100, and 108?

 

[audioguru2]

If the output tuned circuit is peaked at 100MHz (the middle) then it still works pretty well at the ends. Then to tune the frequency you tune only the trimmer capacitor for the oscillator.

Depending on the amount of stray capacitance in your parts layout it might not be able to tune to one end of the dial without changing the tuning coil a little.

 

[ungastm]

thanks for that information..
but why it is still hard to find it on the fm radio?
i even tried moving the dial of the reciever while continously tapping the mic
and while turning the trimmer...
i also tried every positions of the trimmers...

 

[audioguru2]

I don't know how you built it. It won't work on a breadboard and it won't work if the parts are too far apart.  It won't work if wires or a metal case are too close to the tuned circuits. Post a clear photo.

I don't know if the pins on the transistors, voltage regulator or microphone are connected backwards. Is the output of the voltage regulator 5.0V?

 

[Hero999]

Thay may have been breaking the law too. It could have been a pirate station.