Low signal strength

I have a wireless N network set up and have low signal strength in one room in the house. My network is a linksys 300N router hard wired to the source PC and an N PCi wireless adapter card in the destination PC.

The desitnation PC is downstairs, no more 35 feet away directly down the stairs, with only one wall seperating the two PC's.

The signal strength is always low or extremely low and I lose the internet connection frequently.

Any tips on how to increase the signal strength to the downstairs destination PC?

I would appreciate any insight you might have.

 

Thanks, I had thought of that, but the N router should not need an antenna becasue of its strength. The repeaters are not N, they are only G or less. The signal strength in the rest of the house is excellent, there is just something causing a weak signal in the room with the desination PC.

It is a very frustrating situation.