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Thread: Troubleshooting bouncing image from Uno 2400 receiver

  1. #1
    Sky Pirate & FPV Outlaw SecretSpy711's Avatar
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    Troubleshooting bouncing image from Uno 2400 receiver

    Sander to the front desk please... I am troubleshooting a problem I have been having with the Uno (standard version, v3) receiver. When flying at range (~4 or 5 miles with a pepperbox on the GS), the image in the goggles begins to bounce. The best way I can describe it is that there is a little gremlin inside my goggles, smacking the right side of the screen at irregular intervals. When I fly closer, the bouncing stops. When I switch to another receiver, the bouncing is eliminated altogether, and produces a much better picture at these distances. I would expect that an Immersion brand receiver, paired with Imersion and Fatshark branded everything else, would produce the best results, but that is not what I am seeing right now. I am trying to figure out why it's doing this, and correct the problem. I would rather use the Uno so I can have good audio, because the audio is terrible when using the RMRC receiver (I expect this is due to the modulation of the audio sidebands, as the immersion vtx is stereo and the RMRC receiver expects mono).

    To be sure it wasn't a problem specific to my particular Uno receiver, I borrowed a friend's Uno (standard, v3 also) and ran some attenuated tests at home (to simulate flying at long distance). His receiver behaved exactly the same as mine. Here is what I did to simulate what I saw while flying.

    On my plane is a 700mW IRC vtx. I put 64dB worth of attenuators on it to simulate distance. My groundstation is placed at the opposite corner of the room. Then I tried different configurations at the groundstation. 64dB is a lot, but because of the relatively short distance and because RF is still being radiated from the vtx itself, I had to place my hands on the vrx antenna, or remove it, to see any of the same bouncing effects I saw while flying:

    1.) RMRC receiver to 25mW IRC 5.8 relay (my current go-to setup): Placing my hands on the vrx antenna produces some noise in the image, but no bouncing at all. Audio is terrible though. As I unscrew the antenna, picture gets fuzzier, until antenna is completely removed and image goes to 100% noise. But I never see any bouncing.

    2.) Uno receiver to 25mW IRC 5.8 relay: Placing my hands on the vrx antenna produces some noise in the image, as well as bouncing, but the audio is fine. As I unscrew the antenna, the image continues to get fuzzier but never gone, although it continues to bounce. The behavior from my friend's Uno is identical.

    3.) Uno receiver wired to goggles: Placing my hands on the antenna produces some noise in the image, but no bouncing (maybe just some slight waviness at the top of the screen). As I unscrew the antenna, the picture gets fuzzier, but never completely lost. No bouncing.

    So as you can see, if I want to have good audio (for the Vector vario) AND good video (config #3), I have to be tethered to my groundstation, or just not fly very far away. Neither of these is a very good solution IMO.

    I have not posted DVR footage of what I'm seeing because it shows the bouncing as much less severe than what I actually see in the goggles. It also shows it as bouncing up instead of left. I am attempting to find an old camcorder with AV inputs to better capture the raw problem without as much compression.

    Any ideas? Is this maybe due to the filtering in the Uno standard? Would an unfiltered one help? Or could it be an impedance mismatch in the video line? I was considering buying a Duo 2400, but not if it also has this bouncing problem. Any help is appreciated.
    Last edited by SecretSpy711; 30th May 2016 at 07:31 PM.
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  2. #2
    I see you... Derrick's Avatar
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    What does it look like on different video viewing devices? Not saying that it is your goggles, but seems to be something that you haven't investigated further.
    When nothing else out there will suit your needs... design and build it yourself.

  3. #3
    Sky Pirate & FPV Outlaw SecretSpy711's Avatar
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    It doesn't bounce when I wire my groundstation to a 9" display. But that's just a data point for diagnosis, not a viable solution. Therefore it seems to be an interaction between the IRC Uno and the IRC 25mW repeater, when connected together are not able to maintain lock on the sync pulse like it can when the repeater is connected to the RMRC receiver, or when the Uno is wired to a display.
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  4. #4
    What goggles do you have?

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  5. #5
    Sky Pirate & FPV Outlaw SecretSpy711's Avatar
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    Dom V2's.
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    Co-Pilot ImmersionRC Support's Avatar
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    Could you try a different set of goggles with different receiver? My guess it's the goggles or the goggle receiver that is causing this.

  7. #7
    His Royal Sassiness ssassen's Avatar
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    I think the effect you describe is known as 'tearing' which is one (or both) of the sides of the image coming in. This is typically due to a video level or impedance mismatch. Do you have a video or picture showing the effect perhaps?
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  8. #8
    Sky Pirate & FPV Outlaw SecretSpy711's Avatar
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    Quote Originally Posted by ImmersionRC Support View Post
    Could you try a different set of goggles with different receiver? My guess it's the goggles or the goggle receiver that is causing this.
    I tried my raceband receiver (Instead of the fatshark receiver) in my Domv2's and the bouncing persisted. But when tried it with my old Dom V1's, it does not appear to show any bouncing.

    Quote Originally Posted by ssassen View Post
    I think the effect you describe is known as 'tearing' whichs one (or both) of the sides of the image coming in. This is typically due to a video level or impedance mismatch. Do you have a video or picture showing the effect perhaps?
    I always thought of tearing as just part of the image shifting, or kind of a waviness to the picture. What I am seeing is the entire image shifting left by about 1/10 of the image width, for a split second, but it keeps doing it. I don't have video or picture because the DVR doesn't pick it up... it shows as up/down bouncing only, and not as severe.

    The entire link is:
    PZ0420H - Vector - IRC 700mW 2.4 vtx >>> IRC Uno 2400 Standard - IRC 25mW 5.8 vtx >>> IRC or Fatshark goggle module - DomV2's

    All the transmitting and receiving gear is IRC or Fatshark... shouldn't this be working better than with the RMRC receiver?

    Are you suspecting the camera settings?
    Last edited by SecretSpy711; 31st May 2016 at 10:04 AM.
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  9. #9
    Co-Pilot ImmersionRC Support's Avatar
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    Ok if you don't have it with the v1 but do have it with the v2 then it is a goggle issue. I would suggest you contact fatshark to assist you further.

  10. #10
    Sky Pirate & FPV Outlaw SecretSpy711's Avatar
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    I would not be so quick to put the blame on the goggles... I suspect the Domv1's just mask the problem better (maybe because the refresh rate of the screen appears to be slower than the v2's?), just as the RMRC receiver probably masks it as well. It may not be a problem with the Immersion gear (might be the camera putting out an out-of-spec NTSC signal) but I really, really doubt the goggles themselves are the problem... they just show the problem.

    For anyone else reading this that can't figure out what I mean by that, read this, the section titled "Tweaks: Level With Me":
    http://www.rc-cam.com/lawmate.htm

    I need an oscilloscope to really solve this. Is the SainSmart DSO203 good enough for this job? Anyone using it for this purpose?
    http://www.sainsmart.com/dev-boards/...t-version.html

    According to this video, the specs lie somewhat, but it might be good enough to measure the video signal.
    https://www.youtube.com/watch?v=SOdGPUGi9wQ
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