What's the best diagnostic utility for wireless signal?

[Andrew Liles]

I use wireless on a FreeBSD 6.1 box in an area of low signal to my 
Access Point.
I want to be able to inspect the signal strength/quality so that I may 
adjust the antenna to get best results.  What is the best diagnostic to use?

For instance:
    wicontrol wi0
produces:
...
Comms quality/signal/noise:             [ 28 47 1 ]
dBm Coms Quality:                       [ 14 -85 -99 ]
...

but what is "good" or which numbers should I be seeking maximise or 
minimise?