Wireless differences

For years I have been teaching wireless technology using a series of concentric circles to show the distances capable by different data rates of WiFi transmission. (This is all changed now that 802.11n is available). This was always assuming that the devices were using the same antenna, because it was never my remit to go into antenna design.

Here at home I have been using a ZyXEL G200 USB wireless device for a couple of years, which according to my computer has a 16% signal strength at the position and range that I use it. This device uses the ZD1211 chipset. Recently I borrowed a USB wireless stick manufactured by Belkin, and it gave me a marvellous 40% signal strength.

After that, what's a guy to do but buy one of those, and here's where the trouble started. The Belkin part number was F5D7050. From e-bay I bought a Belkin Wireless USB stick, but unfortunately it was a F5D7051. Just one digit different, but it used the qualcom chipset, and I couldn't make it work at all, not even under XP. It is supported in Linux, despite what this site says:
http://linux-wless.passys.nl/query_part.php?brandname=Belkin

So I sent it back, and bought another, but got the right part number this time. It works, but no better than my ZyXEL. What's up? Look at the chart – It is a v4003 version – and has the same chipset as the ZyXEL.

I wonder what chipset was in my original borrowed unit? And do I now have to teach range and speed based on the manufacturer and the chipset used?