Jump to content
Electronics-Lab.com Community

Fm transmitter


Recommended Posts

  • Replies 54
  • Created
  • Last Reply

Top Posters In This Topic

The electret mic must be connected with the correct polarity. Its metal case has the wire that should be connected to the circuit's ground.
The mic must be connected with very short wires or with a shielded audio cable.

You must not touch any part of the circuit when it is transmitting to avoid hum pickup from your hands.

Link to comment
Share on other sites



check this circuit need some help building this one... ;D

Please attach your schematic here instead of over at RapidShare.

The very old circuit will sound bad and have its frequency change when its supply voltage changes.
I don't know where you will find a clip-on heatsink for the output transistor.
Link to comment
Share on other sites

500m through what? Free space, a forest or town?

What receiver are you using? A cheap Chinese FM radio won't be able to pick it up from as far away as well as a state of the art car radio.

What aerial are you useing? A high gain yagi array will transmit/receive the signal from a long away but will be more directional, a simple monopole will not transmit/recieve the very var but will pickup/send the signal in all directions.

Link to comment
Share on other sites


some of the components are not presently available to me to build that circuit...

but i have attached one more file can u provide me some suggestions on it... 

i am not able to attach the file here saying the dir is not writable here...
so i have uploaded in rapidshare sorry for the inconvince.

in this circuit 0.3uH is given how to wind the coil ???

Link to comment
Share on other sites

The simple FM transmitter circuit has its tuned circuit connected to its antenna which causes its frequency to change if something moves near the antenna.
It does not have a voltage regulator so its frequency also changes as the battery voltage runs down.
It does not have pre-emphasis like all FM radio stations have so it will sound muffled like your stereo with its treble tone control turned all the way down.

The LM2931 is a 5V low-dropout regulator. All semiconductor manufacturers make some.
The 78L05 fails when the battery voltage is less than 7V. A 5V low dropout regulator still works perfectly when the battery voltage has dropped to 5.5V.

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.

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.


  • Create New...