More Stoopid Questions

Ok....Thinking of putting an antenna t-connector on my WAP11...I already
have a 24db antenna up on the roof that is connected to one <left> side of
the WAP11, to broadcast to the kid down the street, and the 2nd <rubber
duckie> is set up to broadcast to my laptop inside the house (AP is sitting
in my attic of a 2.5 level home)...

Sooo...if I add the t-connector, AND a 2nd <mfg mismatched 15db> antenna to
that side, how much signal loss can I expect, if any at all??

Also..I have a Compaq WL200 card that is sitting around doing nothing, and
I'm thinking of putting it in somewhere w/ an external antenna hooked up to
it...What kind of a connector will I need for the pigtail?