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:
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