> I attached the cantenna to the WMP11 and used Netstumbler to make
> some measurements. The overall results were disappointing. The
> cantenna didn't give me any improvement over the original rubber ducky

What you haven't said is how far away from the AP you were when testing.
If you're in the same room and already have a good signal, the result
will be masked by reflections and the generally good signal that you
already have.

Try it once you've gone somewhere where the signal is really weak and
then see what difference you have. Or find a neighbours signal with the
cantenna and then take it off and see if it still works.

> than the tiny dongle. Is there a lot of difference in the quality of
> different manufacturer's radios?

Yes.

David.