hardware choice

Hi,

What would be the best AP and antenna for covering a wide area from a roof?

I have a roof, about 35meters high from ground.
on the street, at 300meters from the building where the antenna is, with
line of sight (I always can see the antenna from my PC), I have no
signal....

this is combinations I've tried:

linksys WAP 11
dlink dwl 900 AP+
trendnet TWL310APBX
linksys wap 54g

all this with 12dbi omni antenna or15dbi flat patch oriented antenna.

AP is connected to antenna with coax cable 1meter long of LMR400.

on the street, tested with sena 100mw pcmcia card, SMC 2632w PCMCIA card,
micronet 802.11b pcmcia card, hp iPaq 5450 pocketpc.

Please help!!!

is it a problem of sensitivity or quality of antennas (antennas are from
stella doradus)?

what would be the best solution for "serving a campus", i.e. streets around
and near buildings?

thanx.

SH