So when I’m getting about a kilometer from the TX, my video will start to get blocked up and freeze. Mission planner is showing 100%. I also have the TX on a pole about 20’ up and another 20 or 30’ above the water from our setup location. When I’m flying, I go way father without issue. Could it be I’m in the fresnel zone?
likely Fresnel zone, and multipath off the water.
1 km at 2.4 ghz is a fresnel zone of 5.58766805m radius… so your ground side is likerly ok, whats your air unit antenna height?
Antenna height is about 15cm from the waterline. Guess that would explain the radio/ground control failsafe’s at 1.5km as well I don’t get these issues on the 900mhz frequencies, my gnss rtk corrections on lora and rfd900 radios are solid. Not a good frequency for video unfortunately.
yeah higher antennas
copy and paste
Radiofrequency signals that are propagated over bodies of water are highly susceptible to multipath interference. The water surface, especially if tidal, subject to winds or currents is uneven and extremely reflective leading to the creation of multiple alternate wave fronts and echoes. The temperature interface between air and water can also induce thermal ducting and notable signal loss.
The proximity of the wireless link touch water surface will produce the strongest effects and one of the key strategies for ameliorating water-induced multipath is to raise the endpoints of the wireless link high enough to minimize multipath. If this is not possible, antenna diversity with the erection of secondary parallel links can prove effective. Spatial diversity requirements for wireless links over water need careful assessment and geometric separation to achieve adequate connectivity which is usually planned most effectively by a site survey.
also., 15cm is a bad area
2.4ghz wavelength = 12.5cm
so multipath off the water is likely to cause null’s… ie destructive interference…
also dont forget earth curvature
|1 km||0.00008 km = 0.08 meters|
|2 km||0.00031 km = 0.31 meters|
|5 km||0.00196 km = 1.96 meters|
|10 km||0.00785 km = 7.85 meters|
|20 km||0.03139 km = 31.39 meters|
|50 km||0.19620 km = 196.20 meters|
|100 km||0.78479 km = 784.79 meters|
|200 km||3.13897 km = 3138.97 meters|
|500 km||19.6101 km = 19610.09 meters|
|1000 km||78.3196 km = 78319.62 meters|
So getting my antenna up maybe a meter higher could help… Well, that’s gonna stupid lol! Sure would be nice if there was a wifi repeater I could put at a much higher location. Does anything like that exist for Herelink? I’m thinking the standard wifi repeaters wouldn’t do the job?
we are investigating this, but currently no. i do think getting it up to 1m will still improve things a bit though.