This is a, well, tiny FM transmitter that can have various applications both *probably* legal (pirate radio, your own low-power radio station...) as well as the undoubtedly illegal (FM jammer, spy bug...). The choice is yours!
It can run on a voltage between 3 and 13 volts, draws 2-3 milliamps and has a theoretical output power of ~3 milliamps (although you could easily add an RF amplifier).
I attempted to use a CR2032 with the circuit and, to be honest, i wasnt too sure if it would work. I suspected that something weird would happen when feeding only 3 volts to the 3.3 volt regulator or the vco being too sensitive, etc. However, none of those scenarios came to be true and it worked wonderfully. Although i suspect the output power has gone down, there were no issues and the frequency stayed rather stable.
What frequency did you set? According to the datasheet for 390nH it should be about 103MHz, but I am curious what your effective frequency is. Interesting project by the way.
Could it be possible to get a simple parts list? Just would be easier to know what size of resistor I need to order and so on. (I mean the package size) Thank you so much :)
I had a quick peek at the datasheet but didn't see any specs for the frequency deviations caused by varying the VCC. Did you measure it and determined that a vreg was necessary or did you use one just in case?
I kept it in just in case (since this was my first endeavour into RF/FM, didn't create the original schematic. I found a good one online, re-created it in easyEDA and studied how it works. But I made the pcb layout myself). However, i found out that it worked fine with a 3v coin cell. So, I'm working on a smaller version without the regulator or potentiometer.
That's a good reason. I usually stick to the original schematics (or recipe when cooking) when I do something unfamiliar/for the first time. Then the next time I'm always modding the heck out of it. Better safe than sorry...
it's a bit fiddly but with my mediocre radio and a random piece of wire as an antenna, I managed to get 40-50 meters. I'm also working on a smaller version without the regulator and potentiometer.
What frequency did you set? According to the datasheet for 390nH it should be about 103MHz, but I am curious what your effective frequency is. Interesting project by the way.