GALAXY S4 phone signal reception bocomes very weak when I put back cover

[AC Question]

My samsung galaxy s4 i9500 nework signals become very weak when I put back cover on my mobile.
but it fines when I put off the back cover.
PLEASE HELP WHAT SHOULD I DO?

 

[Tim1954]

Try a different cover? I'm assuming you mean "case" and not the back of the device?