bandpass/low noise amplifier(LNA) & impedance/gain for wifi (PC) cards

Hello,

I want to use a bigger/better antenna (if needed i can post specification of the antenna tomorrow, can't get them right now, sorry) with a wifi PC card (proxim orinoco 8470-WD) on my notebook.

The antenna has a very large bandwidth of frequency, so I wonder if a normal wifi card has a bandpass or just a LNA.
I'm not sure if just a LNA would be enough or if I need to buy a extra bandpass for ~400$ if there is none included in the wifi card...
Or does it not matter to filter the none-wifi frequencys?

Proxim support didn't help and from google I just found out that my card is using a chip from Atheros, but not which one and if there is a bandpass and/or LNA and which characteristica they have :-(

Another thing I'm not sure about is the impedance and the maximum gain.
I know from a wifi modul i used before that it needed a antenna with 50 ohm impedance and a maximum gain of 5dB. Is this for every wifi "thing"/card? Or does it differ from card to card? Did not found any information for my proxim card.

I realy do not understand, why the support is so bad informed and they do not put any useful information in the datasheets....

I hope someone in this forum can help me. Would be very nice :-)

Thank you!

nomex