What is the power (Watt CW) FR4 can handle?

it depends on a variety of reasons such as board thickness, track shape where you handle the power,...

Can I make 7W power amp on FR4 are 433MHZ with 1.5mm pcb thickness and 2.88mm trace width?

7 watts is ok. You might get a little less loss with a better quality board, even at 433 MHz, that might help justify the extra cost. But I would not expect an FR4 board to catch fire or anything at 7 watts.

Of course, you will have to heat sink the RF devices very well. Lots of plated thru via holes, or even better punch a hole thru the board and mount the devices directly to a metal enclosure bottom.

And, of course, the stray heat has to go somewhere--big heat sink or large metal housing.

Don't forget to consider the environment as well. If you have a circuit in an oven the capacity is different than in a refrigerator. Is it in still air or moving air etc.

This looks like a trick question. The RF power amplifier is supposed to DELIVER 7W, not disappate 7W. If it's properly designed, you'll get far less than 7W of thermal energy on the board. The concern should be for the current you intend to deliver through the traces - what's the peak current, and how thick are the traces?

You should visit http://www.rogerscorporation.com/mwu...a/Mwij_vp.html where you can download a DOS program about PC card material used at RF and microwave.

From the attenuation calculations you can estimate the power loss in the attenuation and thus the temperature rise.

By using a thicker substrate you can decrease the attenuation and thus temperature rise.

The material called GETEC or is it GETEK has about half the loss of FR4 and costs less than twice as much.

thanks for your answer

the board thickness is 0.8mm at 2.4 GHz .
i plane to use it for outdoor dipole antenna.
with peak power of 250 Watt CW

thanks in advance

For the calcul,
first I take in count the dielectrical breakdown voltaje (In FR4 is around 11kV/mm), second de dielectric loses (FR4 become too lossy below 1 GHz and complex permitivity varies too much), the dielectric losses traduces in heat, take a criterion for temperature rising, ex: 20°C increase, and upper limit (ex: FR4 can be "destroyed" up to 125°C), ohmic loses in a conductor are also involved etc.

can some knows what is the peak current at base station antennas?

For the main antenna structure, I see no problems at all. Basically the FR4 substrate would be used mainly as a mechanical carrier. A problem may be with the possibly existing transformation element interfacing the dipole to the cable, if designed as a planar circuit. It should be checked for sufficient power handling and losses, too.

Dear bbvv
if we consider 250Watts according to V^2/R and R=50Ohms then V equals (250*50)^0.5 nearly 110Volts. vacuum break voltage is equal to 3000000v/m thus if we consider it for FR4 then 110/0.0008=1100000/8<3000000 which means it doesnt result in break. but there are some hints 1- How much break voltage of FR4 is like vacuum 2- some other considerations such as bends and edges which is thecollection place for Q and ready for discharging and so on...