Inconsistant Wireless download speeds

[cartisdm]

I have a Linksys wireless router on the middle floor. On the top floor I get about 14Mbs download and 2.5Mbs upload.

In the basement I have two desktop computers and a laptop. One desktop (running Mac OS X) gets between .6-1Mbs download and 2.5Mbs upload. The other desktop gets 4-5Mbs download and 2.5Mbs upload (it has two wireless cards I have tried, exact same result on both).

On the laptop I get 12-14Mbs download and 2.5Mbs upload no matter where I am in the basement.

I have already tried changing the broadcasting channel on the router to solve any interference problems and no luck. I can put my laptop right next to the Mac desktop and my laptop still gets good speed.

All of the computers say they have full signal strength. Any ideas?!

[malfunction]

Try moving the antenna - either:

Move them (if they are on cables) - e.g. move them higher / lower and away from the PC case.

or

Angle them (if they are fixed to the card / case) - e.g. if they are vertical try them horizontal.

Also - are all the devices connecting on 'g' or are some on 'a' or 'b'?

[cartisdm]

Try moving the antenna - either:

Move them (if they are on cables) - e.g. move them higher / lower and away from the PC case.

or

Angle them (if they are fixed to the card / case) - e.g. if they are vertical try them horizontal.

Also - are all the devices connecting on 'g' or are some on 'a' or 'b'?

Well now I'm really confused because I'm getting even more weird results. I moved the router to the top of the basement stairs (so like 20ft from computers). The router is broadcasting in b, g, & n and set on auto configuration of the channel (I tried manually setting the channel to 2,3,6,&11 but they only seems to hinder the upload speeds of all computers).

I have been using www[dot]speedtest[dot]net to ping servers. I just tried using different servers (instead of the recommended one which is geographically closest), and I can get the Mac computer up to 9Mbs and the PC desktop to 7.6Mbs. However, my laptop gets 18-19Mbs when I try out different servers. I am so confused!

[Zak33]

The other desktop gets 4-5Mbs download and 2.5Mbs upload (it has two wireless cards I have tried, exact same result on both).

not all wireless cards are equal but some are equally crap!

Which models are the two wireless cards you've tried? I think maybe the lappy has a better wifi chip in it.

[cartisdm]

not all wireless cards are equal but some are equally crap!

Which models are the two wireless cards you've tried? I think maybe the lappy has a better wifi chip in it.

To be honest, the two wireless cards I tried on the PC desktop might be crap. I don't know the internal one but the USB card I tried is a Linksys Compact Wireless G WUSB54GC.

As for the Mac desktop, it's a Mac Pro with two 2.26 quad core processors. I don't know anything about Macs honestly so I don't know how to find out about the card. It's a brand spankin' new computer my boss bought that cost like $4,000. The card is internal and doesn't have an antenna that I can move around.

This is what I found looking around in the computer hardware profile:
Airport Extreme with supported modes ABGN.