Link with 2SXT

hello friends
I have link with 2sxt 5HnD for 2.6km distance but link is not stable, why?

Fresnel zone, signal strength, noise, …

line of side,
noise = -110
Signal rate=-80
is poor 16dbi antenna for 2.5km?
i can see 18dbiantenna(sextant) from 18km with signal rate -85 before alignment.

Hello

Running with NV2 ?

you can contact me at skype : nmthaker

no nv2
I have not Skype but my gmail is zareharofteh@gmail.com
and my yahoo is zareharofteh@ymail.com