Iphone 4 wifi problem..i need help plz

I suspect that my iphone 4 has hardware problem in its wifi and really i need to know your opinion about it..when i connect my iphone to wireless router i found that when my hand just cover the upper silver border of iphone just near to sleep/awake button that wifi indicator in upper status bar in iphone's screen show drop from 3 bars to 2 or even one bar and when i remove my hand from this site , wifi indicator return to full 3 bars again and after searching on Google i discovered that this site which i cover by my hand is the site where iphone 4 wifi antenna present so i tried to put bumper around my iphone's body but this made no difference and this problem persist and now i want to know if this problem occur with my device only so i can change it with another one from store i bought it from or it is general problem occur in all iphone 4 devices so even changing my iphone 4 with new one won't solve this problem??

My iphone 4 has ios 4.2.1

Any help plz

This is behavior by design, I'd assume. If you cover the wifi antenna, you are going to see less wifi signal. I just tested on my device and had similar results (though perhaps not as significant). The short answer is that radio waves don't travel through your hand very well so when you specifically cover the wireless antenna, it's going to impact your connectivity.

Antennagate