If you want to set the transmitter frequency as desired or free one you must have a possibility to change it. That can be done by trimming one of the elements in LC tank circuit. Situation can be fixed inductor (like a resistor or etched on PCB) and variable capacitor (trimmer) or a fixed capacitor and variable inductor.

 

Can the audio Input be a square wave from a 555 timer?

What type of capacitors did you use? It looks like Audioguru used Ceramics (NPO?)

 

Yes of course. Then the resistor that powers the mic isn't needed. The high level from the 555 would need to be attenuated down to mic level. Why make an FM transmitter that buzzes?

Ceramic disc capacitors are excellent for VHF radio circuits. I also used film capacitors for audio coupling. The power supply section has two 100uF electrolytics that are bypassed with ceramic disc caps.

__________________
Uncle $crooge

 

Yea, a tracking transmitter. Its an Idea Ive wanted to test for a long time. Ive come up with the idea since my younger bro likes to get "lost" around the neighborhood. It would be a good way to "see" where is he is, Kinda like GPS, but for the receiver, I would use a field Strength Meter and a regular receiver.

Of course, this thread also gave me another idea, Essentially, It could be used with any Mp3 Player and be able to transmit without the need for wifi. That means I could build a stand alone computer, Put all my Mp3's on it, and Have it play continuously. Then I would also be able to receive it anywhere within the house, Or even Outside.

Is this transmitter AM or FM?

How did you make you Inductor out of PCB? Did you use Eagle to draw the PCB or some other program?

 

AM sounds poor with distortion, noise, interference and no treble audio frequencies. Since its RF frequency is so low, a transmitter's antenna would need to be 100m long. Its inductor would be many turns of wire and needs a ferrite core.

The inductor for FM at 100MHz is only a few turns of wire (or printed traces)with just air as a core.

Instead of making a mono FM transmitter toy that drifts its RF frequency, why not make a Stereo Micromitter that uses a modern IC with a crystal controlled frequency synthesizer and a phase-locked-loop for stability.
http://electronics-diy.com/schematic...ransmitter.htm

__________________
Uncle $crooge

 

Lol, Ive read a couple posts around here that showed that link.

There was a transmitter I found that was made by micrel, MICRF103 (transmit) and MICRF005 (reciever), but they can only be used with digital, and run from 800Mhz to 1Ghz