I am interested in long-range range FPV flying. What things block the video signal of a 5.8gHz video transmitter the most?
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1$\begingroup$ I'm pretty sure it's something like 5.8 has better clarity but is easier to block, and lower frequency (~2.4) is less clear but harder to block. $\endgroup$– GalaxyJul 19, 2020 at 1:31
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3 Answers
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Just about anything will block/interfere with radio signaling if there's enough of it in the path between the transmitter and receiver or in the immediate vicinity of them. (sometimes referrred to as the Fresnel Zone) However, these are some of the most notorious offenders:
- Tight spaces with a lot of multipath interference
- Concrete and brick structures
- Bodies of water
- Soil and earth
- Large structures
- Forests and large amounts of trees
- Lots of human bodies
- etc.
One could go on forever listing out different materials, but these are some of the more common items to encounter for FPV.
In general, the rule is to maintain as much line-of-sight as possible between the transmitter and receiver. This is true because obstacles will force the radio waves to take indirect paths, bouncing repeatedly off of stuff until it hits the receiver antenna. Multipath interference comes from this, because often many different (multi)paths will converge on the receiver at different times and cause interference with each other, distorting the image that your goggles/FPV receiver will pick up.
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2$\begingroup$ I like to tell people that water does a great job at blocking signals. It's the main reason why people and leafy trees tend to block signals as well as they do. The other one that is probably obvious to most people is earth/dirt/ground. It does not take much to completely kill your signal. So be careful when flying behind hills, down into valleys, etc. and as ifconfig says, try to maintain line-of-sight as much as possible. $\endgroup$– 5zero7rcApr 26, 2020 at 13:55
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$\begingroup$ Thank you, @5zero7rc! I added water and earth to the list. $\endgroup$– ifconfig ♦Apr 26, 2020 at 17:08
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1$\begingroup$ Excellent answer. Your multipath comment is of key importance when racing indoors in eg warehouses with metal walls or flooring - as you may not have any line of sight $\endgroup$ Apr 27, 2020 at 9:03
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1$\begingroup$ You might also want to mention the Fresnel zone and how it affects reception: the aircraft does not need to be obscured by an obstacle for the signal to start degrading, it is sufficient for the obstacle to be near the line of sight. $\endgroup$ Apr 29, 2020 at 20:30
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Along with natural structures and other objects, one thing that can really hinder signals is the same material many frames are made of - carbon fiber. So if you use a carbon fiber frame, make sure that your antennas are positioned in such a way that the frame will not block the antennas.
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For an ideal connection you don't want anything to block the fresnel zone. Anything inside the zone blocks your signal. Even the ground when flying low...
