I've been hearing Pawel (and others) talk about "Fresnel Zone" lately, and am considering a micro long-range build implementing 2.4 LoRa technology (Ghost).  I started looking into it and it can become quite a rabbit hole.

Just to see if I understand the basics - it is important to fly "within a clear Fresnel zone" of your Tx's and Rx's, correct? I interpret this to mean that I need to fly high enough so that no obstacles protrude into the 1st Fresnel zone.

I found a Fresnel Zone Calculator: https://www.everythingrf.com/rf-calculat...calculator

So if I want to fly 5km,  I need to check both 5.8gHz and 2.4gHz.  Here's what I get:



So for video, my "line-of-sight" needs remain clear of obstacles by at least 8 meters - and for radio, it needs to remain clear by at least 12.5 meters.  That sure doesn't seem very far.  So if I fly at least - say 30 meters - above any obstacles between me and my quad, I should be OK (as far as Fresnel zone is concerned) - correct?

Ah yes, good ol' "picket fencing".  It can be an issue for mobile Ham operations.  Particularly in the PNW with all those trees.

I know with voice comms you have to be very close to say trees to have a problem.  So based on that experience, and your calculators it looks good to me. (actually more distance than I would have believed.).

I'm interested in what our experts here have to say.

Yeah, me too.  I brought it up because, I saw the term "Fresnel zone" once again in a comment posted to the video below.  Dave_C had mentioned he was flying this quad from another mountain about 3km away from this one.  The commenter said "keep that good fresnel zone!"