Jump to content
Electronics-Lab.com Community

Urgent help for a transmitter


Recommended Posts

i m tryin to construct a telephone fm transmitter which connects to the phone line in series. i have used two schematics from the internet but both fail to work, i dont know what is the problem. all the soldeing and circuiting is fine. but is it because of the inductor wire? cause i am using a 0.75mm thick wire[about 21 gauge], i also tried the capaciter trimmer for my second circuit but i heard nothing on the radio, all the components are exact, except for the transistors which i replaced with ones with similar characteristics.

please anyone out there, help me,

Link to comment
Share on other sites


You changed the transistors but you forgot to tell us which ones you used.
You forgot to show your pcb so we can see if the wiring is short enough for 100MHz.
At 100MHz, a wire is an inductor. If the wire is longer than about 3mm then the inductance is too high.
Wires side-by-side have capacitance between them If the wires are high impedance and are side-by-side for more than 3mm then the capacitance is too high.

Don't use a breadboard for 100MHz circuits.
This FM transmitter had its parts so far apart that the wires between them had too much inductance. It didn't work:

post-1706-14279143337415_thumb.jpg

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
  • Create New...