Help with medium range transmitter??

[limlim500]

Hey, i am building the medium range transmitter (http://www.electronics-lab.com/projects/rf/025/index.html)

I am having problems because i have built it from the schematic and it will not work. the only difference is i used a 5-65pf trimmer instead of a 4-40pf transmitter since they dont sell them and that was the closest match up. would this make a big difference? i've used all the same parts and transistors etc, can anyone help me figure out whats wrong? also is it meant to transmit in AM or FM? and for the audio input would a headphone input be ok?

any help is appreciated. liam.

[audioguru]

Hi Limlim,
Welcome to our forum. ;D
It is a very low power, very poor quality FM transmitter:
1) Its antenna is connected to its tuned circuit so that if anything gets near the antenna then its frequency will change.
2) It doesn't have a voltage regulator so that the frequency will change as the battery voltage runs down.
3) It doesn't have the pre-emphasis (treble frequencies boost) that FM radio stations use, so an FM radio will reduce the treble frequencies making the sound very muffled.
4) It is mono, not stereo.

Your tuning capacitor should tune it to the low end of the FM dial.
Its input resistor is for powering an electret microphone. It is too sensitive to be fed the high level from a headphones jack.

It operates at 100MHz which is a Very High Frequency so it needs to be made on a pcb or on stripboard. A breadboard has too much stray capacitance and should not be used.