How do I increase the range of this RF transmitter?

[tackyattack]

What is the easiest, cheapest what to increase the range of this RF transmitter? Right now it outputs 8mW which gives it about a 500 foot range. I need it to be increased to about 40 miles line-of-sight.
http://www.sparkfun.com/products/8946

[Averagesupernova]

If we tell you, you can expect large fines from the FCC.

[tackyattack]

If we tell you, you can expect large fines from the FCC.


Is it even possible though?

[KingNothing]

Remember the inverse square law.

http://upload.wikimedia.org/math/4/a/0/4a0aa41bf97d4c8c39824c42fbf7a2a5.png

You are asking to increase the distance by a factor of about 500. Since the intensity is proportional to power and inversely proportional to distance squared, you would need to increase the power by a factor of 250,000!

The little device you linked to would go up in smoke.

[vk6kro]

You would need a linear amplifier with an output of about 10 watts and a suitable directional antenna.
That is 31 dB so the amplifier would need to be multi stage. Quite a project at 433 MHz.

This is a small band of frequencies for low interference devices like garage door openers and short range brief data transmissions. It was sliced from a long standing Radio Amateur band.

10 watts would cause chaos in this band and would bring immediate attention to your activities. Transmitting substantial power in this band is probably illegal in all countries.

If you want to talk to a friend 40 miles away, you could use Skype on a computer, or you could get a Ham Radio licence and have plenty of fun.
With a Ham licence, you could use repeaters which relay the signals from low powered transmitters and transmit them at higher power from high locations.

I think Citizens Band operators have similar repeaters on about 460 MHz and these may require a licence but no technical study.
Check your local regulations and stay legal.