problem in my Fm transmitter

[haitham al-saab]

Hello every body
I'm glad to register in this forum it is one of the good forums that I've seen.
Dears I have a project which is about creating a Fm transmitter I went to the shop and I find all the component except some capacitors
that I fell to find it so I forced to create these value by adding capacitors in parallel or series
this scheme of the project
**broken link removed**
this is after the modification
**broken link removed**
and this is real pic
**broken link removed**
my question I'm I right when I replace the C
the second question I fell to make it work and I really do not know why can you guess where is the problem

 

[Audioguru]

I could not find the faulty original schematic at Circuits Today.

1) the value of C4 is so high that it cuts almost all audio frequencies. It should be 0.002uF (2nF), not 0.2uF. An FM transmitter is supposed to boost high audio frequencies, not cut them.
2) Your schematic shows the second transistor upside-down. Its collector is supposed to connect to the LC tuned circuit.
3) Your schematic is missing a very important wire connecting the collector of the second transistor to the trimmer capacitor.
4) There is no way your tangle of wires will work at 100MHz on a breadboard because its capacitance between the rows of contacts is too high and the inductance of your long wires are too high. Use a compact pcb instead.

Here is the fixed original schematic and your schematic:

 

[haitham al-saab]

I could not find the faulty original schematic at Circuits Today.

1) the value of C4 is so high that it cuts almost all audio frequencies. It should be 0.002uF (2nF), not 0.2uF. An FM transmitter is supposed to boost high audio frequencies, not cut them.
2) Your schematic shows the second transistor upside-down. Its collector is supposed to connect to the LC tuned circuit.
3) Your schematic is missing a very important wire connecting the collector of the second transistor to the trimmer capacitor.
4) There is no way your tangle of wires will work at 100MHz on a breadboard because its capacitance between the rows of contacts is too high and the inductance of your long wires are too high. Use a compact pcb instead.

Here is the fixed original schematic and your schematic:

thank you veru much
Thank you for your quick response. I really appreciate your
some guys said to me that I can not use this board as you said also to crate a high freq fm trans
how can I redesign it ,so that it can work in this board even if I change the freq the important point is to make it work as an Fm trans ?
regards

 

[Audioguru]

45 years ago I made a similar FM transmitter shown on a magazine on perf-board. The wires on the board were as short as possible. It worked but sounded muffled because it was too simple and was missing pre-emphasis (treble boost).

8 years ago somebody posted an FM transmitter circuit on this forum and complained it did not work. It had some errors that I corrected. I built it compactly on strip-board.
I added a voltage regulator and pre-emphasis so it worked perfectly and sounded good. Its range is more than 2km to my very sensitive home FM tuner and high quality car radio. Its range is 300m to my cheap Sony Walkman FM radio. Its range is across the street to my cheap clock radio.
It is here:

- - - Updated - - -

I notice another error on the schematic you found. The capacitor feeding the antenna is shown as 0.022pf which is impossible. It should be 22pF to 100pF.

 

[haitham al-saab]

Tank you very much
I'll try and try until I got it
Your advice is more valuable than gold for me