Hi Peter,
I do not have a radiation pattern created in Fluke Airmagnet, but this is the data sheet for the WS-AP3805i and has radiation patterns for both radios. (I'm assuming you likely have already seen this but did not see a reply to your post)
http://www.extremenetworks.com/product/ap3805/
If there is a big discrepancy in the signal you're seeing, perhaps it is due to country or channel/config settings. If needed, we could open a case to investigate for you.
Thanks,
Jason