Video falling apart when plane is pointed home

[AaronHartwell]

In an effort to get cleaner video and more range, I spent the better part of the day yesterday rewiring the video system (CAM/OSD/VTX) in both of my planes with shielded USB cable. I was previously using twisted servo wire.

Tonight I took my planes out for a test flight to see if the new cabling made any difference. I was able to go out past my previous record of 3.2km to 4km. I'm using a standard 72mhz radio so control ends up being the thing that limits my distance.

Overall the video was OK on the way out. At 2km I started seeing the small lines that I've been working to clear up. At 3km, the screen rolled a few times but it wasn't bad. I think it might have been marginally better than before the rewire. At 4km I could still see relatively well but my radio's fail safe was kicking in so I decided to be greatful for the new personal best and turn back.

And that's when the wheels came off... As I was making the turn things were fine. Once the plane was pointed directly at home the video completely fell apart! I was able to see the OSD well enough to keep her pointed home but it was rough. The video slowly got better as I got closer to home and it finally cleared up when I got within 2km.

Here's a video:

http://youtu.be/sFFkAj1_x9E


Here's my theory on what might be causing this...

My camera is encased in a metal case and is mounted on the very tip of the nose. Slightly behind the camera and on one side of the fusalage my vTX is mounted. If the plane is returning home pointed straight at me the vTX antenna is unobstructed. If the plane is angling just right the camera ends up being between the ground station and the vTX antenna. See images below...

Could that be the problem???

Interestingly enough, I flew the second plane (which I had also just rewired) to test it out and saw EXACTLY the same thing on the return to home. Decent video going out, fine through the turn, terrible when the plane was pointed directly home. Same camera, same VTX, different plane but roughly the same mounting locations.

Specs on the plane in the video:
Lawmate 2.4ghz 500mw VTX
Lawmate 2.4ghz receiver with 8dbi patch antenna
Skylark OSD II
SecurityCam2000 Sony 600 TVL cam
Fatshark Dominator Goggles
Futaba 9CAP 72mhz
Pinnacle Dazzle Base Station Recorder

[aeryck]

Without watching the video, I'd have to say your vtx antenna is too close to your metal-encased camera, and is causing all sorts of reflection. I had an issue with a 5.8ghz system I was testing out; whenever I was flying right to left the video would start dropping out like mad. As it turned out, the metal camera case was between the vtx and ground station every time the video went to hell.

Try relocating the vtx further away from the camera, if you can.

[Mark Hitchman]

A fairly easy fix might be to stick the VTX to the back of the camera, I used to do this but now put the VTX on a wing.

Mark

[SENTRY]

http://fpvlab.com/forums/showthread....RN-AROUND....&

[AaronHartwell]

Sentry - I watched your videos. Correct me if I'm wrong but it looks like you were seeing interference on the turn but things got settled out pretty quickly after the turn? In my case, things are clear during the turn as the plane is banking. They go haywire once I'm pointed directly home and the video stays bad until I get fairly close < 2km. That's what's leading me to think something is blocking my camera signal vs. a polarization issue.

Mark and Aeryck - Thanks for the responses guys. I'm looking at the plane trying to find alternate mounting locations.

[SENTRY]

^ Please read the entire thread I linked. You are seeing the exact same thing. You learn more from reading that thread than looking at the videos.

[AaronHartwell]

Sentry - Heh... But I love videos. I'm reading it now.

[SENTRY]

Thank you sir - you'll be a smarter operator afterwards.

[Scotttu]

Here's a video:

http://youtu.be/sFFkAj1_x9E

This video contains content from EMI, who has blocked it in your country on copyright grounds.
Sorry about that.

My country is about 11 miles from you Aaron...

It may be ugly but you gotta get that away from the components and out on the wing.

Just watched the previous video and I can see lines on hte way OUT but not back in (Before rewire)...

I bet if you got a 16" USB shielded cable and ran an extension and put the VTX out on the left wing your lines would go away..

the ONLY time Ive had that noise on the way back was at Mt Si and it was because:
a) A kid moved/blocked/disturbed my antenna.
b) Someone powered on their cell phone within 50 yards of me..(By the signal bands in the noise I believe this the cause)
c) The Nghobbies PSU was pretty beat up and lifting pads too so that my have done it.


View this video on YouTube


In your case I would absolutely expect noise on the way back - you are blocking your antenna and you are too close...

Found the original post in my EZ Build - you might have a work around there by going up above the canopy:

http://fpvlab.com/forums/showthread....ll=1#post64502


2 miles out over Poulsbo, had a little bit of wireless out there but not bad, I hardly saw it while flying it but the DVR caught it.
NGHobbies PSU removed, TBS CORE installed:


View this video on YouTube

[AaronHartwell]

Thank you sir - you'll be a smarter operator afterwards.

Sentry - More informed for sure.