Radio transmitter and Receiver

Harmony

How can I use radio wave to turn on/off a siren? I think it is possible for me to design a radio signal through this schematic:
http://www.aaroncake.net/circuits/fmtrans.htm

The problem is, how do I design a receiver that can switch on a siren by receiving the radio signal?

berkeman

You could use a cheap radio receiver, and just bandpass the audio output to look for the tone frequency that you would be transmitting.

The circuit you show is for a typical low-power, unlicensed radio transmitter. The range of these transmitters is about 10m-20m, so don't expect too much. You also have to tune them to an open station frequency, so if you are in a highly-populated area with lots of FM radio stations, you will have trouble finding an open frequency.

You might consider using an IR link instead of FM. You could start with a kit, like the one in the lower right corner of this page:

http://www.transeltech.com/kits/kits1.html

pulsemaster

Try using a garage door opener system.
Two reasons.
1-you need a transmitter on a set frequency that trans mits a code
2-you need a receiver that receives a set frequency that needs a code to turn the power on.
Instead of the door opening and closing you could have the sireen latch on or off and the security of any hacker reduced.
good luck

elec2050

you would get ready wireless modules from Link Technologies they make ready modules you can further connect a buffer relay to switch on / off the siren

Rick