Many in the WISP industry will repeat an oft-stated fact: Trees are the enemy. This may be overdramatic, but trees can really ruin an otherwise nicely operating wireless network. As a rule-of-thumb, for most WISP operations you require line-of-sight or near-line-of-sight. Different frequency bands respond to obstructions differently:
When planning wireless links, you want to start by searching for line-of-sight. From the receiver, you should be able to visually see the transmitter (and vice versa). Trial-and-error may permit other links to work (especially the lower frequencies), but it is not a good idea to count on it. It is generally easier to increase the elevation of the receiver or transmitter (or saw down a tree!) than it is to rely on penetrating the foliage.
Fixed obstacles such as buildings and mountains cannot be reliably penetrated, and you should search for paths around them.« Chapter 4: Fade Margin and Rain Fade Up To Contents Chapter 4: Fresnel Zones »
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