I have used two types of Orinoco cards on Linux with two different radio chipset and different drivers for both. I guess the card your are describing is known as the 8470-WD, which uses the Atheros chipset.
This is a PC-card with external antenna connector and I have one of those myself. It works very well for me on Linux, at least when using Kernel 2.6.10 or later together with the Madwifi drivers:
http://sourceforge.net/projects/madwifi/.
Of course an antenna will extend the range of the card. Most antennas use N-type connectors or SMA-connectors. To be able to connect with thoose you need a pigtail between your card and the antenna cable.
Regards
Nicklas