Significant loss of speed through wireless router?

I have a Comcast cable connection with a supposed 6mbps line. This bears out when I use the CNET speed test. It shows about 5200KBPS as a result. When I run the same test, at about the same time of day, on my Dell Inspiron 9100 laptop, which has a built-in "Dell Truemobile 1300 WLAN PCI Minicard" the result is 2032KBPS.
Is this the best I can expect, or is this an excessive loss that can be tweaked or corrected?
The router is a D-Link DI-624M Super G MIMO, and it sits about 15 to 20 feet away. I have it placed on the stairs in the basement, while the laptop is on the first floor of the house. The straight line distance has a good bit of lumber in the way(stair supports, wall, etc.), but I don't think there is any sheet metal in the way to block the signal.
Thanks,
Vic

 

I have a linksys router and a 7000k connection.

I get 6800 to 7000 on my wired machines but 3200 on my wireless machine connecting with 54Mb wireless connection.

I think the wireless overhead may be slowing it down.

 

Speed drop

Thanks Scott. So I guess a 50%-60% drop is "normal ".
Vic

 

That is my experience but I can't explain why?

 

USR seems to have an interesting article on this. I'm sure there are others:

http://www.usr.com/download/whitepapers/80211g-wp.pdf

I wonder if there are settings that can be optimized on a wireless access point or in Windows that can help get more of the speed across. Even at 11 mbps you wouldn't think there'd be that high of a % of difference.

I remember wondering why I couldn't get 100Mb/s or even close over a wired network. I suspect some of it is the Windows machines themselves ...

Could we set for different MSS or such settings and get some improvement?

Make sure nothing else is around (cordless phones?) on 2.4Ghz.