Diagonal lines - RC Groups
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Nov 15, 2012, 10:20 PM
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Diagonal lines

hey all.

I don't post much here on rcg, but i'm having a problem i can't figure out.
I have recently completed my fpv quad, and am getting diagonal moving lines in the picture. I'm using an immersion tx, immersion uno receiver, dragon osd and pixim cam. I do have a lc filter installed.. I've tried to use a sepparate lipo to power only the video equipment. No difference. But what i did notice was that when i touch the cloverleaf antenna, the lines dissapear.. anyone got an idea?

Boring video showing what i mean..

non fpv flight (7 min 25 sec)
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Nov 15, 2012, 10:38 PM
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Daemon's Avatar
I've seen a lot of different examples of diagonal lines, caused by
noise from speed controllers, BECs, motors etc, but I don't think I've ever seen
any that were as soft and vertically oriented as those. Whatever it is
appears to be very close to in-phase with the video signal itself, so I'm
guessing it's coming from somewhere within the video signal
path itself. Maybe a ground loop. I'd probably start by bypassing the
OSD just to simply the video path and see if it helps.

Nov 15, 2012, 10:50 PM
Registered User
Ok, i will try to bypass the osd tomorrow. this is my setup scheme by the way. any errors?
Nov 15, 2012, 11:03 PM
Yeah, that's pretty weird for them to be vertical. I would try removing all of the
crap in between the VTx and camera and then adding things back in one at a
time to see what component is causing it. Or even if it is a manufacturing error
if it's occurring with just VTx and camera.

Nov 15, 2012, 11:14 PM
Registered User
Gonna try tomorrow. It's 5 in the morning here now, so i'm going to get some sleep. strange thing is though that when i touch the antenna, it'gone..
Nov 15, 2012, 11:47 PM
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Daemon's Avatar
That behavior is not uncommon and unfortunately doesn't really help you narrow it down.
Could mean the video signal is getting transmitted, and then picked back up
by some other component.

You do have a couple ground loops. One on the ESC/Naza side.. as you've
got a high current ground path through the ESC and a low current ground path
through all the ESC control wires through the Naza FC. Could try running
just the signal wires alone, but I doubt this is the issue.

You also have a potential ground loop (depends on design of Dragon OSD) on video side.
You've got a ground path associated with the current sensor signal to Dragon OSD
(without an LC filter), and another running from the high current side of the current
sensor through your regulator and LC filter. If the Dragon OSD shares its
grounds internally, then that's a likely cause of the noise. If so, disconnecting
the ground from the current sensor signal path should fix it.

Last edited by Daemon; Nov 16, 2012 at 12:34 PM.
Nov 16, 2012, 07:06 AM
Registered User
I tried to bypass the osd a minute ago. So just power to the video tx and camera. disconnected everything from the osd just to be sure. But again, no difference.
Moving lines.. But when I touch the antenna or video in, it stops (or at least it's getting way less visable..). Also tried the stock antenna's. same result.

Will try removing all grounds fom the esc's. thoughi also doubt this will change anything, but it's so annoying..

As for the Dragon osd, i will post my wiring scheme in the dosd thread, let the experts have a look at it. I realy don't know if it's a closed circuit. i think so, because you need to place a jumper to power the osd from the current sensor.
But i think i ruled out the osd by bypassing it.
Nov 16, 2012, 08:16 AM
Registered User
removed the esc grounds. no difference.. i'm beginning to think the tx is broken..
Nov 16, 2012, 08:59 PM
Registered User
ok, so i can be certain that somewhere i have some current running back through the ground lines.. and if i understand right, looking at the number of lines moving throug the picture it's caused by an (internal) power regulator.. as far as i can tell i have things hooked up in the way of the diagram in the link. only problem is that my wiring is short. it's a tight fit on a quad.
But if i only have the video tx and camera powerd on, and an lc filter in between, this means the interference is coming from either the video tx, or the camera..? the power regulator which lowers the voltage to 12v is filtered by the lc filter right? so what can i do about it?
Nov 16, 2012, 09:45 PM
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Daemon's Avatar
I don't think it's from a voltage regulator. The lines are too close to being in sync with the video signal.
Usually voltage regulator noise is finer and more horizontal, way out of phase with the video.
All I can figure is your video Tx Rf signal is being picked up by either the camera itself
or one of the wires coming from it (signal or ground) and retransmitted. Maybe try adding
some ferrites on other wires.

Nov 17, 2012, 12:28 AM
Registered User
I'm going to try and make a new wire harnass. separating all cables from each other to try and find the source, since i used the original connector and a piece of the cable from the pixim cam. And make a new lc filter, since this is the only component i did not exclude. by the way, does it matter if i used both the audio ground and the video ground of the camera? I'm not using audio, but i ran the ground back anyway. I tried disconnecting each one of them. same result.

Tried a torroid as big as my thumb on the ground from the tx, and on theground of the power supply, just behind the regulator. no difference until the top of the picture started to pull to the right..
also tried it on the video line to the tx, did nothing but take away my colours..
Nov 17, 2012, 12:38 AM
Registered User
Daemon's Avatar
Before you do all that, try connecting your otherwise unused audio signal wire to ground.
One potential source of video noise, is an overdriven, or free floating audio signal.

Nov 17, 2012, 05:27 AM
Registered User
Sorry.. My mistake.. No audio ground. There's a +,- video signal and video ground coming from the cam. I soldered the ends of the - and video - to the ground lead. Guess it was pretty late last night..
The only thing left is the LC filter, or the cables..

So while i'm at it, which cables are best used?
Last edited by lennie054; Nov 17, 2012 at 05:46 AM.
Nov 23, 2012, 05:06 PM
Registered User
After making a new wire harnass, and rewinding and resoldering the lc filter, i found out that a torroid on the vtx 12v line makes it almost dissapear..

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