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Help with FPV feed please
#1
Hey guys I really need some help diagnosing this issue with my FPV feed. No clue what is going on, getting lots of flickering and sometimes losing the video feed all together. I have a 1000uF cap on the power into the PDB but no LC filter. Could not having a filter be degrading the signal that badly?

Equipment:

Googles : Eachine VRD2
VTX : Foxeer TM-25 Switcher
Camera : Foxeer HS1177
OSD : Piggy OSD

As you can see in the DVR footage the video is getting breakup like crazy. Some things I have done to try to fix this. 

https://www.youtube.com/watch?v=rURn3HQB...e=youtu.be

ried new VTX, same model
Flown a different quad with same goggles, works just fine
Re-soldered the connections to the OSD.

Excuse the bad flight. Was flight LOS which I'm terrible at and was in horizon mode which shakes around a lot. (If anyone has any advice on how to tune self leveling let me know lol I'm still new.

Heres DVR footage with a brand new vtx of the same model just out of the package


https://www.youtube.com/watch?v=fIT2CiEa...e=youtu.be

[/url]Anyways any help would be awesome because at this point I don't even feel comfortable flying FPV for fear I will lose video feed and crash into the neighbors or a car. Please help.

[url=https://www.rcgroups.com/forums/editpost.php?do=editpost&p=37890879]
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#2
It doesn't look that bad to me. You are getting some breakup due to multi-pathing and certainly, your quad doesn't seem very well tuned with the wobbling that is present in the video.

You're also getting significant signal degradation when you go behind the trees, which to a degree is to be expected as 5.8GHz signals are very much line of sight.

What power level were you running your VTX with during the flights? What antennas do you have on your VTX and your goggles?

If you want your videos to appear in your post rather than just showing as links, remove the &feature=youtu.be from your URL before pasting it into your message. If I take the URL of your first video and just add
Code:
https://www.youtube.com/watch?v=rURn3HQBjNs
to this post, you'll see the video embedded.

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#3
Also, if that's you standing at the end of the house then it's no surprise that you almost completely lose the video when you fly to the other end of the house and put the house between your goggles and the craft. FPV video will not travel through buildings!
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#4
Ah thanks so much. This was at 200mW. Yea it has not been tuned at all its my first build. In horizon mode the wobbling is really terrible. I only use it when landing or flying LOS so I haven't fixed it yet. the VRD2 comes with a circular polarized and a patch antenna using diversity. Not how good these eachine antennas are though. VTX antenna is Aomway CP antenna. Bumped my vtx to 600mW to improve signal penetration. One of the problems I had with it is that I have had the screen go completely black on me, which I'm not sure what would cause that. Has happened a few times but usually is rare. Possible damage to the VTX or not likely. Maybe the googles as they are on the low end obviously.

I know that 5.8ghz doesn't have the best penetration but I didn't realize that just one tree could degrade the signal that much. I'll have to do some more testing to see if I have signal completely drop again.

One last note, how the heck do you tune the self leveling modes in betaflight lol. I understand how the PID's effect the behavior, but what is the D setpoint weight and transition. I'm thinking thats causing the wobble in horizon mode so badly? The first vid is horizon second is acro. I know the PID's need a lot of work but acro is worlds smoother than horizon for me.

Thanks again sorry for rambling lol
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#5
PIDs do contribute to all flight modes, but if the craft flies well in acro mode then I'd suggest that you reduce the "Strength" setting that's listed on the PID setting page for Horizon. This parameter controls how aggressively the craft attempts to self level and if it's too high, you'll get exactly that kind of wobbling.

If you'd asked me to guess what power level you were running at, I'd have bet on 25mW. At 200mW and flying less than 50 metres away, those trees shouldn't have any major effect on the signal.

Given that you are getting such terrible performance, I'd suspect that the antennas don't all have the same direction. I'm sure you know that circular polarisation can be either left handed or right handed. If you mix the two directions, you'll get awful reception. Do you know what polarisation the various antennas have?

Also, a really silly question, but are you sure that the connectors are all the same? i.e. that you have SMA to SMA or RP-SMA to RP-SMA? If they are not the same, then one way, it won't be possible to connect the antennas, but the other way, you can screw them together, but they won't really be making a connection inside.
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#6
(12-Jul-2017, 10:07 AM)unseen Wrote: (...) but they won't really be making a connection inside.

...which would mean the vtx would quickly burn out - you might even still receive a signal, but a very weak one.
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#7
I'm assuming you mean as far as the vtx with the vtx antenna right. The connection type doesn't have to be the same for the antennas on the goggles as the antenna for the vtx am I right? It's just how they connect to the vtx or goggles. I'm the polarization side I'm actually not sure that's a great point I will be checking that in a second. Also on the second video link I did realize I had the vtx set to 25mW, but the first one was 200mW
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#8
It seems both antennas are right hand polarized. The vtx side is sma and the reciever side is rp-sma but they both have the correct respective antennas so I'm assuming that has nothing to do with the signal they send.


Edit: I think my VTX antenna is LHCP -_-.... no wonder im having such issues lol. Feel dumb now
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#9
(12-Jul-2017, 09:48 AM)Phoenix132 Wrote: One of the problems I had with it is that I have had the screen go completely black on me, which I'm not sure what would cause that.  Has happened a few times but usually is rare.  Possible damage to the VTX or not likely.  Maybe the googles as they are on the low end obviously.

Black screen is most likely the OSD shutting down. This is a common problem with minimosd and is normally caused by noisy 5V supply

In general:
Black screen and OSD -> camera problem
Black screen without OSD -> OSD problem
Snow -> VTX problem
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#10
(12-Jul-2017, 01:11 PM)fftunes Wrote: ...which would mean the vtx would quickly burn out - you might even still receive a signal, but a very weak one.

Not always.

Firstly the female parts of the SMA connectors are often a fraction proud of their PTFE insulators and if you screw two female connectors (of SMA and RP-SMA) together hard enough, you can get what looks like a good connection with a multimeter.

Secondly, there are various design strategies that will mitigate the risk of damage to the output stage of a transmitter from excessive reflected power. If you look at how complex the output stage of a TBS Unify VTX is, and compare it to a €10 Eachine VTX03, you can understand why the cheapo designs blow up the first time the antenna is disconnected in a crash. I've heard of people accidentally having run a Unify VTX at 500mW without an antenna for over 30 minutes with no obvious damage to its function.

But, back to the OP's problem...

There has to be something wrong, either with antenna polarisation direction (my current #1 bet), antenna placement (some photos of the quad would be good to check that), or maybe (just) some interference from 5.8GHz WiFi (which in the US at least clashes with some of the standard FPV channels).
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  • KonradS
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#11
(12-Jul-2017, 04:42 PM)Phoenix132 Wrote: Edit: I think my VTX antenna is LHCP -_-.... no wonder im having such issues lol. Feel dumb now

Just saw your edit.

No need to feel dumb if that is the problem. I only buy right hand polarised and only buy SMA so that something as simple as not being so sharp one day doesn't have me accidentally using wrongly matched antennas without noticing until I suddenly lose video.

I was out earlier today flying my Atom which uses one of the Eachine VTX03 transmitters. With a beaten up linear antenna on the VTX, I could get perfectly clear video at 25mW to a linear antenna on my SkyZone goggles at up to 130m. This was with line of sight.

I've noticed on other quads that trees will give significant interference once they get larger if the power is only 25mW. Even 200mW won't make the signal stay clear behind a tree though but it will remain good enough to see where you are flying.
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#12
Yea the new antennas come in Friday. Will update with results
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#13
Yeah i should have said "could" burn out. From what i've read it seems that even a pigtail connection could provide enough resistance to save the vtx from burning?

Anyway, just to add, i once was flying with a broken antenna without noticing - i had clean signal for a good distance until i turned the quad around so the frame carbon came in between line of sight and the vtx... that's when i noticed. Big Grin
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#14
Ah yes, the old "I'm blind!" moment. Big Grin

Terrifying isn't it?
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  • campagnium
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#15
(13-Jul-2017, 09:34 AM)unseen Wrote: Ah yes, the old "I'm blind!" moment. Big Grin

Terrifying isn't it?

You could't imagine how much... i tried actually split-s-ing a large metal tube lol... instead i rammed it hard Big Grin
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