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LarvaX video breakup... VTX? Antenna?

Frisbee

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Hi All, a few days back my antenna popped off my LarvaX. I put it back on and it seemed to fly good as new, and then I had a light bong on the underside battery, and immediately the video started breaking up. Now when I fly I get video breakup, blackline static, and a bit of a jump (image moves upwards), whenever I get about 20 feet away. It's disorienting enough that I can't safely judge where obstacles are at. Any thoughts on a possible fix?

Antenna?
Connection between Antenna and VTX?
VTX?
Connection between VTX and camera?
 
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Frisbee

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Cheers, I removed the hood and made sure the antenna was securely attached. It seems to snap-lock into place. (I'll get the e6000 either online or see if the local craft store is open if that might help to lock it down all the way.) I've still been able to fly my LarvaX (not too aggressively), but the breakup at critical moments definitely leads to some crashes.

Is there any likely cause of the static? Maybe the VTX overheated? It does get really hot.
 
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rtkDarling

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I used that e6000 to attach a small circular polarized antenna right to the hood, now i get clear reception until i failsafe. I had the original antenna coming up through a slot in the back and glued to the pod as well, keeps crashing pressure off the board.
20200526_144755.jpg
 

HighTechPauper

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There is always a chance that the vTX is damaged somehow, they don't last forever anyway since RF components age and drift with time even without crashing. What frequency is the goggles and vTX set to? Can you post a DVR of the issue?
 

HighTechPauper

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Hey @Frisbee, the more I think about this, 2 things jump to mind...
The vTX is an RF amp and they get hot enough to burn you quickly, they are fairly sturdy generally (even without an antenna now), I would look hard at the antenna, it sounds like the ground or center conductor broke away from the U.fl is my guess. If the quad got hit enough to pull the antenna off it may have broken the connection because they are super fragile, I've seen it a few times on mine. Try a new antenna first, and If you cut off the heat shrink that is holding it together you can probably verify it visually. They often over crimp these connectors and it breaks the strands of the wire, a little bit of movement and they break.
 

Frisbee

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I used that e6000 to attach a small circular polarized antenna right to the hood, now i get clear reception until i failsafe. I had the original antenna coming up through a slot in the back and glued to the pod as well, keeps crashing pressure off the board.
View attachment 4342
Are those the LUMENIER MICRO AXII U.FL 5.8GHZ ANTENNA (RHCP)? Looks really good the way you have it mounted. Wayno mentioned those in another thread, but they were a bit too expensive given I'd probably lose them in a day, but maybe with your e6000 method they wouldn't get lost. If they're significantly better than the basic ones, I could try upgrading.



There is always a chance that the vTX is damaged somehow, they don't last forever anyway since RF components age and drift with time even without crashing. What frequency is the goggles and vTX set to? Can you post a DVR of the issue?...

... The vTX is an RF amp and they get hot enough to burn you quickly, they are fairly sturdy generally (even without an antenna now), I would look hard at the antenna, it sounds like the ground or center conductor broke away from the U.fl is my guess. If the quad got hit enough to pull the antenna off it may have broken the connection because they are super fragile, I've seen it a few times on mine. Try a new antenna first, and If you cut off the heat shrink that is holding it together you can probably verify it visually. They often over crimp these connectors and it breaks the strands of the wire, a little bit of movement and they break.
The frequency used is 5.845 GHz, which seems to be optimal. I removed the hood and checked the connections, and everything seems connected. I think you might be right about the antenna getting damaged, because the heat-shrink did get pulled off. I'm waiting on several spare antennas to ship, and I could also upgrade to the better one.

Do you think that a low power disarm will improve the lifespan of the vTX?

Cheers for all the replies. In the meantime I'm still having a blast flying. I've adapted a bit by planting myself in the center of where I'm flying, and if the image goes bad I try to fly back until it clears up. It isn't as clear as it was out of the box, but it's definitely flyable, and I'm still getting better (at the basics) daily.
 

HighTechPauper

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Do you think that a low power disarm will improve the lifespan of the vTX?
Yes, just like running a fan or unplugging power to the vTX while working on the bench can help. I haven't used low power on disarm though for a couple of reasons...
I run Smart Audio and LUA scripts so I can turn the power down if I choose, but if I need the video feed to help find my quad using the quad finder function of my RX module then I often want the extra power to help with that.
 

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