Help Understanding Video Interference

[bhagerman]

This is my first foray into FPV flying so it's likely I'm the cause of the problem, but I can't sort out what the solution is. I built a small wing (the mini arrow) with the following components:

Battery: https://store.flitetest.com/lumenier-1000mah-3s-35c-lipo-battery-xt60/
Motor: https://store.flitetest.com/emax-motor-mt2204-kv2300/
ESC: https://store.flitetest.com/blheli-series-12amp-esc-xt-30/
Receiver: https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=91061
Trans + Camera: https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=81335

The transmitter and camera rig are powered via the balance lead from the battery. As it stands, when I power everything up the video is clear. And if I test throttle with no prop attached, the video also remains clear all the way up to 100%. However, once I have the prop installed, I get full video loss past a certain throttle threshold (unfortunately this threshold is much lower than what's necessary for flight). The video isn't somewhat obscured, the feed goes to full blown static and only reappears once I throttle back down. I understand that there can be interference caused from the ESC and motor power, but I'm not sure if this is the case here. There's some interaction with the lead going from the ESC to the receiver (at moderate throttle the video occasionally appears if I move the cord, but the behavior isn't very consistent). If that is the cause of the signal loss however, I'm not sure what the appropriate fix is. Appreciate any advice or troubleshooting tips and can post some photos of the setup if that helps at all.

 

[PsyBorg]

2 questions come to mind. First how close is your VTX to an ESC. Second do your camera wires run anywhere near the ESC wires?

I ran my VTX on top of my quad and made sure the cameras wires were as far as possible from any esc wires. If your wires have to cross at any point make sure its at a 90 degree angle. If they are parallel the esc's can induce so much noise it could easily cancel your video signal. Camera is low voltage signal and an ESC is high current pulsing which creates an emf field around the wires. That magnetic field can jump to other wires if they are within that field and or they are not shielded somehow.

I think most of the builds for wing style FPV airframes run the power distribution to the motor on the centerline and the video stuff off on a 45 degree angle away from all that. If you have to balance the offset of the VTX you could always run the battery and esc in the center line and split your receiver off to the opposite side of your VTX but I don't think that little bit of weight would be a major issue in that regard.

If you look at that pic you can see all my flight control wiring is on the bottom plate and my video runs along the top and my vtx and antenna are at the highest point during flight. Where it does cross past that rear esc it is at a 90 degree angle exposing as little as possible to any emf fields being produced

 

[kerrycorcoran]

If you're powering the vtx and cam directly from the battery (12v) you would definitely want to have an LC Filter in-line to clean up the dirty DC current. Typically this will cause lines, however you may have so much interference the signal is getting stomped.

This at least worth a shot and you can DIY it too.

 

[kerrycorcoran]

I would also throw an LC Filter in-line just to make sure you're cleaning up an dirty DC current.

 

[bhagerman]

Thanks for the replies.

@psyborg fairly close, but about as far away as I could get it (following the fpv build plans). My vtx and camera wires do run near the ESC, all the wires pass through the center pod. That being said there is probably a proper orientation that I may be missing. I'm attaching some photos of the layout:




@kerrycorcoran that's probably a good idea. I had previously had a fat shark filter off the balance lead powering the vtx and camera but it was recommended I use the balance lead directly to help troubleshoot my camera issues. The poster seemed to suggest that I wouldn't have much problems with the balance power, but clearly I don't know what's what hah. I do think that if its a dirty current it's getting blown out by the other source of interference so I want to lock down a solution there to start.

Does it mainly come down to the orientation of the ESC and vtx wires? Which wire interactions are the most problematic? There's the lipo to ESC, lipo to vtx, vtx to camera, or ESC to receiver, and with limited space it's hard to have everything not touching hah.

 

[PsyBorg]

My vtx / camera set up came with a premade cable that I integrated into my quad after tying in a battery warning buzzer since the harness came ready to plug into the balance connector from the battery. No filters or anything which makes me think your issue is from inductances created by the esc. You could pick up a ferrite core (circle made with iron composite) and try wrapping the wires between the camera and the VTX a few times. That is also commonly used to clean up signal inductance issues with sensitive electronics and RF signals.

The most interference should be from the ESC forward to the motor and the most sensitive part for the FPV to take in interference is between the camera and the VTX if its RF related which sadly are right next to each other. Leave your esc to motor connections straight in line but off to one side of your compartment. Take the wires from the camera back to the VTX and bend them 90 degrees and route them away from the side you routed the esc wires. See what changes that brings you. That would at least give you an idea if it is RF related if it changes and power related if it does not.

 

[JimCR120]

If you're powering the vtx and cam directly from the battery (12v) you would definitely want to have an LC Filter in-line to clean up the dirty DC current. Typically this will cause lines, however you may have so much interference the signal is getting stomped.

This at least worth a shot and you can DIY it too.

First a disqualifier, I haven't done realtime FPV yet, just post-flight FPV.

I too had a thought about the one battery powering both systems. If you have a spare battery I would be curious if powering the camera from a separate battery would make a difference. I know when I power my iPod through the cigarette lighter I can hear audio interference that corresponds with the engine rpm. Checking with a 2nd battery (1 for flight systems & the 2nd for FPV) will put them on separate power sources and could help steer you to the solution.

 

[bhagerman]

Wanted to update and say thanks again for the replies and advice. I went back in and tried a few options for the placement of the ESC battery line with respect to the rest of the vtx and camera cords, and at least within home testing it seems to have done the trick. I'm honestly surprised I could get a clear signal given the level of interference with just some alignment tweaks but lesson learned hah. I'm going to look into a possible filter or ferrite core but seems like this setup will get me in the air for a first round FPV test. Again, appreciate the help, hopefully can report back with some footage at some point!

 

[PsyBorg]

Good to see you might have this resolved. Its frustrating when you look at your gear sitting there in front of you instead of in the air. Yes some video would be nice. Maybe a before and after for comparison.