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Old Dec 21, 2015, 06:34 AM
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range question - 2km with 2.4g?

Can I get reliable control for around 2km with some combination of these?

Flysky Th9x, have Frsky DJT module with patch antenna and Orangerx dsm2/x module with simple antenna
or
Walkera Devo 6s with nrf2401 with pa

and

Frsky dr4-II
or
Frsky d8r-xp
or
lemonrx dms2 6-channel
or
Walkera rx601

This is for a boat, there will be trees and some small hills in the way at the end of the range.

I'm quite happy to build antennae and mount them on the boat, and on a tripod at the dock.
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Old Dec 21, 2015, 08:21 AM
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There are 3 things that will affect the range. The first is the height of the transmitting antenna, secondly the RF level radiated by the antenna and thirdly, any obstructions between the transmitting and receiving antenna.

There are other factors that could come into play and atmospherics (weather) is primary. The affect weather conditions will have at the edge of your operating area is one of those things that can't be easily calculated or estimated. Suffice it to say that rain and fog will definitely reduce the usable range as the water in the air will effectively absorb RF energy.
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Old Dec 21, 2015, 09:41 AM
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I have a friend who flies his DX9 2.5 MILES away FPV, so 2km is going to be nothing.

Andy
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Old Dec 21, 2015, 09:44 AM
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This ought to perk up the thread!
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Old Dec 21, 2015, 12:22 PM
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Quote:
Originally Posted by BoxCar31 View Post
Suffice it to say that rain and fog will definitely reduce the usable range as the water in the air will effectively absorb RF energy.
Yes water in the atmosphere can attenuate the signals.

But that fact is not very helpful, you need to say by how much the signals are attenuated.

If its only 1% say, its not worth considering really.
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Old Dec 21, 2015, 12:31 PM
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2.4 doesn't go around things very well, a different frequency might be better in this application.

How are you going to see the boat, video transmission back will have the same issues.

My RC set gives 100% signal quality at over 500m height (say 800m total straight line distance), but if it lands in the grass and I put my Tx down, at 50m it's less than 50%.
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Old Dec 21, 2015, 12:31 PM
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Read rule7 of the attached PDF
better yet, read the entire set of rules -it does apply to our use of 2.4
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Old Dec 21, 2015, 05:23 PM
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The rub

Quote:
Originally Posted by srnet View Post
Yes water in the atmosphere can attenuate the signals.

But that fact is not very helpful, you need to say by how much the signals are attenuated.

If its only 1% say, its not worth considering really.
The rub is it depends on the percentage of water in the air and the size of the droplets.
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Old Dec 22, 2015, 08:05 AM
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And how high above the lake surface you are.

Reading again, that he's going to be around trees, he needs to use a lower-frequency radio - something in the 30-75MHz range according to local laws for surface vehicles.

Andy
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Old Dec 23, 2015, 11:35 AM
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Quote:
Originally Posted by BoxCar31 View Post
The rub is it depends on the percentage of water in the air and the size of the droplets.
Ah so you dont know.

My recollection is that the effect of rain etc on 2.4Ghz comms is insignificant.

If you look it up you will find a figure of 0.005dB per kilometer in moderate rain quoted. So the effect can be ignored.

Atmospheric attenuation of radio wave starts to be come a significant issue above 10Ghz however.
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Old Dec 23, 2015, 11:42 AM
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Ah so you dont know.

My recollection is that the effect of rain etc on 2.4Ghz comms is insignificant.

If you look it up you will find a figure of 0.005dB per kilometer in moderate rain quoted. So the effect can be ignored.

Atmospheric attenuation of radio wave starts to be come a significant issue above 10Ghz however.
The 10 commandments I posted pretty well outlines the majority of questions - there are no absolutes here .
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Old Dec 23, 2015, 02:04 PM
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Quote:
Originally Posted by richard hanson View Post
The 10 commandments I posted pretty well outlines the majority of questions - there are no absolutes here .

Indeed there are no 'absoloutes', but atmospheric absorption in the context of 2km RC links at 2.4Ghz is still insignificant.
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