need help with an FM transmitter

[absolution]

ok heres the deal. for class i have to design a powerfull fm transmitter. must be stable so gotta use a crystal. its gotta be narrow band so +or- 3khz was my teachers specs. I'm tryin to pull off at least a 4 watt. all schematics ive found are 12 vlt and i need one to run off a 9 volt battery. if i can get a schematic even close this rating at 9vlts i should be able to modify it myself. :shock:

 

[Nigel Goodwin]

ok heres the deal. for class i have to design a powerfull fm transmitter. must be stable so gotta use a crystal. its gotta be narrow band so +or- 3khz was my teachers specs. I'm tryin to pull off at least a 4 watt. all schematics ive found are 12 vlt and i need one to run off a 9 volt battery. if i can get a schematic even close this rating at 9vlts i should be able to modify it myself. :shock:

They usually run off 12V for the simple reason that cars mostly have 12V batteries - as well as that, 9V batteries are usually very small and only low power - a 4W transmitter will take a good amount of current.

If you can modify it yourself, why not start with a 12V circuit and modify it for 9V operation?.

 

[absolution]

i know it would take a bit so i was gonna use nickel metal hydride or at least i think thats how its spelled. im basically tryin to get as high powered as i can with the stability of a crystal. i've seen 2 watt transmitters but they didnt have the stability of a crystal. i asked for 4 watt to see how high i might make it. a 2 would work just as well. im just trying to get higher than 1 watt.

 

[audioguru]

A little "9V radio" size of Ni-MH rechargeable battery produces 7.2V and has a capacity of 150mA/hrs. It has an internal resistance of 1 ohm and therefore will have a loaded voltage of 6.3V when charged. Its voltage will drop to 5.5V when it will need recharging.
If your 4W transmitter is 75% efficient, it will draw 5W from the battery. If the transmitter is designed to be operated with a 6V supply, the average current from the battery will be 833mA and it will last about 11 minutes.