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Radio controller antennas question.
271 6 6-13 08:22
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Raf_IZ0QWM
Second Officer
Flight distance : 262523 ft
Italy
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Please DJI guys can you help me solve a forum thread?
You know how much I am interested in antennas and radio transmissions, I guess you have seen it in some post on DJI FPV.
This time I need a hand, that is, a written confirmation.

I was able to open the housing of the MavicAir 2 remote control antennas and I saw that there are two folded dipoles, dual band with reflectors.
This means that the radio is capable of some kind of MIMO or diversity technology.

Well, can you confirm that the antennas are dual band, by writing it to me? And not that one side is for 2.4GHz and one for 5.8GHz.

Moreover, I have also seen the reports that DJI has sent for the FCC that are available on the internet and everything confirms what I write.

I thank you for the great work you do.

6-13 08:22
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Raf_IZ0QWM
Second Officer
Flight distance : 262523 ft
Italy
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I will do some measurement tomorrow. Now I can test the stock antennas.
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6-13 12:31
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Raf_IZ0QWM
Second Officer
Flight distance : 262523 ft
Italy
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Tested today.
So both antennas are dual band. VSWR is good for both.

The doubt remains about MIMO or Diversity (SIMO), I will do further tests because in the FCC document an RX antenna and a TX / RX are highlighted

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6-14 00:48
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Raf_IZ0QWM
Second Officer
Flight distance : 262523 ft
Italy
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I wanted to do this test to make it clear that if you want to improve, modify the remote control must be done in the right way.

Using one antenna for 2.4GHz, and one for 5.8GHz, as I have seen done, makes everything DJI has put in place to improve signal reception in vain.

The MIMO technique is well known in the WiFi field, it uses hardware and software to reconstruct, thanks to the use of multiple transmitting and receiving antennas, the radio signal bouncing off obstacles (multipath).
It takes advantage of the multipath, which is usually deleterious for single antenna systems, to decrease the latency often due to the request for repetitions of packets.


https://www.edn.com/understanding-mimo-part-ii/



The more you know your drone, the more you have a safe and a happy flying always.
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6-14 20:24
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kyalami
First Officer
Flight distance : 11007070 ft
Sweden
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Raf_IZ0QWM Posted at 6-14 20:24
I wanted to do this test to make it clear that if you want to improve, modify the remote control must be done in the right way.

Using one antenna for 2.4GHz, and one for 5.8GHz, as I have seen done, makes everything DJI has put in place to improve signal reception in vain.

Very interesting. Thank you for your explanation.
6-14 21:51
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Northwood
Captain
Flight distance : 978934 ft
Canada
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So in your last post you X out the Yagi-Uda add-on....  you are saying it does not help?  I found that for me it does actually improve things.
6-15 06:25
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Raf_IZ0QWM
Second Officer
Flight distance : 262523 ft
Italy
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Northwood Posted at 6-15 06:25
So in your last post you X out the Yagi-Uda add-on....  you are saying it does not help?  I found that for me it does actually improve things.

Yagi-Uda? Oh no I didn't say Yagi-Uda don't help but they should be the same on both antennas. Now post another image.
The antennas must have the same left and right gain.
If you use one for 2.4GHz on the right and one for 5.8GHz on the left you will have one side that gains more and one less and this does not help the MIMO algorithm which will always lean towards using only one antenna.

What you see in the picture is a Yagi-Uda modified to become dual band.

I tested 5.8GHz Yagi-Uda antennas before building those dual bands.
There is indeed an improvement, as was to be expected.

Sorry, only in italian.
By making this video I discovered that the remote control antenna has a reflector behind it and therefore is in effect a Yagi.

6-15 08:44
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