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2.4 GHz directional RX/TX 17 km

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KZ0FOX's picture
2.4 GHz directional RX/TX 17 km

I plan to setup a Rocket M2 at 33.265978,-96.7601066.  The closest node is KF5NNY-LittleElm-North at ​17 km away and may be up on a water tower.  I can get about 25 feet high at my location in North Texas.  Is it reasonable to expect a Ubiquiti PowerBeam (PBE-M2-400) or airMAX RD-2G24 to work?  I would like to gauge my probability of success before I invest the time.  I prefer to use a cheaper Yagi antenna if I can source one with gain/noise specs for this application.

Thanks for your suggestions.

KE2N's picture

The height above ground alone does not tell you if it will work. The important thing is whether or not you have a clear Line-of-Sight path to the other end.  If you can see the top of the water tank with a pair of binoculars (or telescope) from your intended antenna location, you are probably going to get a signal.

Bear in mind however that you should keep the Fresnel zone of the signal path clear of obstructions to avoid fading and multi-path.  One guideline is 80% of the zone should be free of objects.  At 17 km and 2.4 GHz, 80% of the Fresnel zone is a 50 ft radius at mid path.... the radius is smaller near the ends of the path.

I like to use to check out prospective paths.  there are a number of other tools.


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KZ0FOX's picture
2.4 GHz directional RX/TX 17 km

Thanks for your help.  Originally I was questioning expected versus specified 20 km performance of the antennas.   I incorrectly assumed my area is relatively flat.  The tools show that I would need a 20+ m mast to even attempt line of sight on the closest nodes, even if they are 30 m above ground.  I suppose now I will switch over to the tunnel forum.

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w6bi's picture
Relay node needed!

Judging from your diagram, a node on top of that hill to connect the two endpoints together would work, too.  Or, another one at their same level that could route around the obstruction.  Not knowing your exact topology, it's hard to say if either is feasible.  And of course, there's always site access.   Is there a repeater system in that general area that has coverage of both end points?  If so perhaps you could talk the system owner into placing a node there.   Having network access to a repeater can be an incentive :-)

Orv W6BI

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