Ok I did some better tests today. I had a helper to be my pigeon bird. I used Google earth to measure distance.
I found one device that would play along with me at 5Ghz, its a laptop so I am sure there is a antenna near the screen attached to the adapter on the mainboard. The routers antenna's are orientated at different angles. Its location is about 20ft above ground surrounded by single pane windows/walls with no insulation to outside of house.
Laptop using a ubuntu generic driver:
5Ghz, Max coverage enabled, power 100%, 20 Mhz channel bandwidth -- 429ft
2.4Ghz, Max coverage enabled, power 100%, 20/40Mhz bandwidth, 600ft before disconnecting, then reconnecting at 400ft.
Changed hardware on router and testing device:
2.4Ghz, antenna from a tp-link 2.4ghz router, 1 factory antenna in middle, a (3X longer) 9dBi 2.4Ghz ebay antenna, all orientated vertically. I shut down 5Ghz on router. I used a Samsung Android tablet.
2.4Ghz, Max coverage, power 100%, 20/40 bandwidth, my pigeon got to 1,400ft away from the house. I had the tablet setup to view the wireless log in the router refreshing every second.
That coverage is crazy. I think that ebay antenna makes a world of difference and I would say my laptop may not be as good as some of the android devices when it comes to weak signals or transmitting power..
Sorry Matt I forgot to try 5Ghz at performance.
Edit: I should add there is only 1 other AP running 2.4Ghz feq and I do not overlap his. My RSSI floor/noise is -92dBa