help 900MHz antenna tests

I currently have an omni directional antenna with dbi of 11 on top of a 250ft tower
That I am testing
The results so fare are not good
I cannot pick up a signal in treed arias.
I have gone out 2.5 miles where I can see the tower and get a god signal
But if I go out the same distance in a Simi treed aria I get no signal
I have picked up a signal at 2 miles out behind a small tree line witch was just one line of trees with an open field on thy other side and I also had the SM on a 15ft pole.

I called tech support and they said that they have not tested with a 360-degree antenna only a 60-degree. They also said that morn then likely I signal is week because its attempting to cover to brood of and aria witch is making the signal to week to pass through the trees and its working as a line of site antenna

Can I get some help?

Can you all post your results with the type of antennas your using?
Any input would be greatly appreciated

what you quoted from tech support is exactly your answer. an omni directional antenna isn’t going to give the same distance as a directional antenna. with the MAXRAD antenna supplied with the radios i have seen coverage through trees at about 3.5 miles; thick trees at 2.5 miles. i think you might need to consider 6 APs with 60 degree antennas for your cluster rather than one AP with an omnidirectional.