Hi!
There is a circuit diagram of FM Transmitter circuit in the page: 2 km FM Transmitter Circuit Diagram, Working and Applications. In this post, it is mentioned that the transmission range is upto 2km. I want the transmission range upto 25 km. by using the same circuit. So, what are the modifications to be required for this circuit? Is it possible to further increase the transmission range?
Kindly suggest me the solution. I would like to do this project on next week.
In most countries it is illegal to own and USE transmitters in the FM band. It's very difficult to get an amateur-built transmitter sufficiently narrow-band.
An increase from 2 to 25 km, require approximately 150 times more power. Put down the project and build something that does not interfere with radio broadcasts.
Pelle
There are two ways to increase range - more power or more directional aerials.
However highly direction aerials like a Yagi rely on line-of-sight paths, which is
unlikely for 25km.
The regulations for transmitter power typically limit ERP, not just total output
power, so a higher gain transmitter aerial wouldn't normally be legal. Higher
gain receiver such as a large Yagi or dish is perfectly valid though.
With all due respects, if you don't know what's involved in increasing a transmitter's range then you have absolutely no chance of building a working FM transmitter.
Such work requires a good understanding of electronics and how components which aren't even connected to each other can influence device operation simply because of their physical proximity to each other.
If you really do want a high power FM transmitter then your only chance of success is to go out and buy one. If the law of your country prohibits this then so be it.