Our wireless network at work...Cisco 4402 WLAN controller and 33 Aironet 1230 access points. One particular access point is mounted on an inside wall, there is a hole punched through the wall, and it is connected to an AIR-ANT2465P-R antenna. It is mounted externally to the parking lot so LEOs can pull up and upload video from the DVR systems in their cars.
Today, sitting in my truck with my laptop about 60 feet away, I had a Very Good to Excellent signal at 54mbps. If I pulled a file off one of our file servers, I get the max speed I'm expecting. If I upload a file to a server, it is extremely slow and sometimes just stops altogether. If I pull up within 15 feet of the antenna, same results. The LEOs are complaining about slow upload times for the DVRs and rightfully so as I have discovered.
There is another Cisco aironet inside the building. I have not yet taken my laptop inside to connect to it and test. The WAPs are running on different channels, 1 and 11. No other wireless networks around according to NetStumbler.
Insure that your antenna has enough downtilt to cover the area you planned for with appropriate electron dispersion. Also insure that the polarization of the antenna is proper with the antenna mounted with the cable leads in either the 6 or 12 oclock positions. Beamwidth on this antenna requires some downtilt as electrons are dispersed in a more predictable manner with a slight bit of downtilt.
I would start by isolating whether this is a wireless issue, a network issue, or an AP issue. Go hardwire in and test the connection to make sure that the wireless AP is the culprit. Then go test at different APs to see if you have the same problem.
No reason to spend a lot of time troubleshooting this AP until you're sure it's the AP :)
It helps immensely to have the duplex and speed settings on the switch port set to auto rather than 100 full. Switch log was full of duplex mismatch errors. Corrected that and now everything works like it's supposed too.