Wasn't it cfs717 who wrote:

We all know that it is imposibble to see a planet from other solar system
nomatter how powerfull a telescope might be.
Because the light from the Star is so bright  that it cover-up the dim light

>from the planet.

We also know that a Star emit radio wave.
Won't that radio wave from the Star cover-up the radio wave from the planet
where ET live?

The radio output from a star has an extremely wide bandwidth so although
the total power output is extremely high, the output at any one
individual frequency is quite moderate. 

An artificial signal intended to be used as an interstellar signal would
be designed to have a very narrow bandwidth. So although the total
amount of power is a small fraction of the total power output of the
star, the power at that particular frequency can be much higher.

For example, the FAQ mentions that Arecibo can be used to transmit with
a band width of 0.01 Hertz, whereas the emissions from a star would be
typically spread over many GigaHertz, so only a few quadrilionths of the
star's output is likely to fall in the particular 0.01Hz band chosen by
ET for their signal.

-- 
Mike Williams
Gentleman of Leisure