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5.8 gHz antenna on 2.4gHz DJI Controller

Discussion in 'FPV (First Person View)' started by THOM FERRELL, Nov 1, 2015.

  1. THOM FERRELL

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    I have the New Style DJI 2.4gHz Controller for my Phantom 2.( The one with the Dial for the Gimbal)
    I'm changing the antenna connection.
    Can you use a FatShark 5.8 gHz
    5.8GHz Fat Shark ImmersionRc RP-SMA Antenna (RHCP)
     
  2. Mark The Droner

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    My understanding is it might work but it probably won't work well. That's because the 2.4 ghz signal fluctuates at less than half the speed of a 5.8 ghz signal. Because of that, it's a wider signal. That's why CP antennas such as cloverleafs and helicals are built in size relative to the signal (5.8 ghz antennas are less than half as big as 2.4 ghz antennas). You might use that antenna temporarily, but I would get an antenna made for the 2.4 ghz range.
     
  3. kenjancef

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    So this got me thinking.... I've see a few controller mods for better antenna signal strength but they seem to consist of actually modifying the controller. With a 2.4GHz antenna, would a swap-out bring a gain in signal?
     
  4. Mark The Droner

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    You have "a bunch of very expensive antennas" according to your sig, so I am guessing you already know the answer...

    We're talking about the 2.4 Ghz control transmitter, right?

    If you have a 2.4 ghz antenna on there which is omnidirectional, and you swap it out for a directional antenna, of course you will have better gain because you are forcing the signal away from other directions and into another specific direction. Just like a lamp vs a flashlight. Hence, the need to aim the antenna/signal at your target. Or if you have a directional (e.g. half sphere helix) and you swap it out for a higher gain directional (say 6 turn helix), the beam-width becomes narrower, so gain increases, but you must be even better at aiming. If you're not, then the antenna is worse outside of the beam.
     
    #4 Mark The Droner, Nov 2, 2015
    Last edited: Nov 2, 2015
  5. kenjancef

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    No, he antennas are for my FPV. I watch and rewatch videos and read as much as I can, trying to wrap my head around the differences between helical, patch, CP, SMA, and all of the other acronyms. So I do have a set of SpiroNETs, a patch, and just ordered a shorter CP antenna because I remounted my Immersion and the Fatshark I have now is too long. So I'm just trying to be silly, and serious at the same time. I don't want to spend all my money without understanding why I'm spending it...
     
  6. Mark The Droner

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    Haha. Okay. I'm learning this stuff too, I'm no antenna expert. ;)

    I think the first thing you need to ask yourself is what do you want out of your set up? Super long distance? Or just general good range.

    If it's super long distance, is it going to be over farm land or over water?

    If it's over land, then I think you'd want to lean towards a CP helix. A long CP antenna will shoot that signal out like a laser. But you have to be willing to aim it and steer your craft in one direct line. I would look at google maps and line it out perfectly so that while you're flying FPV you can steer the craft towards your goal... which might be the corner of a corn field or a small pond or whatever which you have mapped out in advance and which is a mile or two or three or four away. That way you know it is going in a perfect straight line. Then of course, you want to aim your CP sniper rifle antenna in that exact line and don't you dare move it. You might even set it on a table or a tripod or something.

    And of course you'd want to have receiving antennas on your craft that match the polarization of the transmitted wave.

    For FPV, you could do the same thing. The same idea applies, but you'd want the signal to spin the opposite way so they'd have a less chance of interering with each other. So one way to set it up is control might be LH and the FPV might be RH. Or vice versa. That way they won't interfere with each other because they will be blind to each other, since a RHCP receiving antenna can't see a LH circulating wave.

    But if you plan on going long range over water, maybe you'd prefer a linear signal. Because you can get the advantage of the skip or bounce over the water which would not work with CP because the CP signal will bounce and then spin the wrong way after hitting the water - like a mirror.

    On the other hand if you just want a nice general but still powerful set up, you might think in terms of a shorter CP (which would have a broader transmitting beam) such as a half sphere or even a linear antenna.

    Or best of all, have antennas for every situation. :D

    So that's my weak understanding of it all............
     
  7. kenjancef

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    Pretty much general good range, haven't flown enough yet to trust it going too far, even though I'd keep it in LOS.

    That sounds like a good idea, but I would think there wouldn't be too much interference because the quad is 2.4 and FPV is 5.8, correct? Or would there still be interference anyway?

    Yea, I don't need to go too crazy yet. I'm just finishing getting my FPV to work right... lol... I wasn't sure if the controller antenna could be upgraded just as easy as on FPV. I never really tried unscrewing the antenna on the controller yet.

    Not weak... made sense to me. I still have more reading/watching to do, so I'll get it all sorted out eventually. I appreciate your post and your NOT WEAK info... :)

    I know someone here had posted a picture of their controller with a HUGE helical antenna on it, it looked pretty awesome, and he said he got awesome range with it. Maybe I'll get there someday. My only fear is loosing my quad...
     
  8. Mark The Droner

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    I agree. One would think there would be little interference since the two signals are completely different frequencies. But then again, if there is even the tiniest chance of a tiny bit of interference, why take the chance?

    I think having the right antenna set up is so important, much more so than adding a booster. I once visited the Green Bank West Virginia space telescope facility and in there they had a demonstration of a parabolic antenna. At one end of a large room up near the ceiling was a lamp - just a normal omnidirectional lamp. At the other end of the room was a parabolic type of mirror that was pointed at the lamp. It was maybe three feet in diameter. So what the visitor was asked to do was place his hand at the focal point of this parabolic. So I placed my hand in the air and moved it around until I found the light hitting it. Then I moved it forwards in back until the light came to a point. And I held it for a few seconds. The lamp was just an ordinary light source and it was maybe fifty feet away, but I could actually feel the heat of the lamp on my hand.
     
  9. jason

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    The antenna on your controller is not screwed on but held on by a plastic collar. Yes you can upgrade the RC antenna but to do so is direct violation of FCC part 15. Flight distance for the stock RC/P2 according DJI is 1000m (3280.84') but some have flown a stock unit 2 miles over unobstructed terrain.

    I think you are confusing 2.4GHz antenna system with 5.8GHz FPV system.
     
  10. Mark The Droner

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    <buzzkill>

    Why do you think that?
     
  11. kenjancef

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    He's talking about my signature. I am talking about "expensive antennas" for my FPV setup. I went through a few before finding something that works. I am also replacing the antenna on my ImmersionRC on my Phantom because the one I have is too long, it hits the ground. So I'll have a few spares floating around...
     
  12. jason

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    Reread your statement about the controller antenna it marked in red

    "Yea, I don't need to go too crazy yet. I'm just finishing getting my FPV to work right... lol... I wasn't sure if the controller antenna could be upgraded just as easy as on FPV. I never really tried unscrewing the antenna on the controller yet."

    "The antenna on your controller is not screwed on but held on by a plastic collar. Yes you can upgrade the RC antenna but to do so is direct violation of FCC part 15. Flight distance for the stock RC/P2 according DJI is 1000m (3280.84') but some have flown a stock unit 2 miles over unobstructed terrain."


    You can think whatever you wish.
     
  13. kenjancef

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    Well since I never tried anything with it, I wasn't sure if it unscrewed like a regular antenna. Now that I know you can't, then I'll just leave it be...
     
  14. kminton327

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    [QUOTE="jason, post: 562633,Flight distance for the stock RC/P2 according DJI is 1000m (3280.84') but some have flown a stock unit 2 miles over unobstructed terrain.


    Got exactly 1 mile out of my p2 over slightly obstructing terrain with the stock set up. Dji was a little off but I suppose they had a reason for saying that