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Oct 19, 2015, 12:18 PM
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markm75's Avatar
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Audio hum in the feed when connecting a camera with power to Vector? Ground loop?


The gist of my issue is that when i connect either the surveilzone cc1529 or the runcam hd (with 3 pins, one being power in either case) to the leads off my vector, this results in a background hum or buzz in the audio feed (even without a microphone or audio line being sent out)..

If you unplug the camera, the sound goes away..

To me this sounds like a ground loop issue, though i'm still a novice in tracing how to fix this, i was pretty sure i had things setup to avoid a ground loop, well at least with the ESC's.

Without a diagram this is basically how i have things wired..

Battery --- power connector --- Vector Current Sensor --- ESC connector..

All of this goes back to the Vector.. and i also have a 5 amp ubec that fees off the + - of the vector current sensor and plugs into the left side of the vector, giving 5v to that left side (yeah i know i didnt really need it, but rather than trying to run esc to the vector to provide the 5amp, i chose to use a separate supply)..

The place i knew i had to prevent a ground loop was at the wing, where i have a single servo connector coming off of the two motors.. on that connector i pulled the red pin to avoid a ground loop at least here.

I'm not sure where else i'd have a ground loop.. i'm guessing the red pins going back to the camera, but those need power.

The vector has 5v and 12v options for the camera power.. i've tried both as well (at least with the cc1529 which supports 5-12v etc)..

Any thoughts out there?

Thanks in advance
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Oct 19, 2015, 05:36 PM
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Ok I tried removing the bec power from the vector while using the runcam hd cable with the red power connector pulled, so strictly one power source going to the vector.. same audio hum.. I guess this rules out a ground loop.. back to the drawing board and unsure at this point

I thought maybe i could try putting an ic filter between the battery and the rest of the setup and see if it helps, though i'm doubting it will.
Last edited by markm75; Oct 19, 2015 at 05:52 PM.
Oct 20, 2015, 09:18 AM
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I put the circuit filter in the mix and this made no difference.. at this point i'm assuming the background hum when the camera is connected is "just how it is" or perhaps the RMRC 800mw transmitter somehow is related to it.
Oct 20, 2015, 10:47 AM
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Tom T's Avatar
Try turning down the black and color brightness of the OSD. I forget exactly which one was doing it on mine as its been a while since I had the hum. Also, does your vtx have a left and right audio out? Try tying them together (make them into a mono source) as one may be emitting an audio signal that is getting picked up some how. Ive read that you can also ground one side (left or right) output of the vtx to snuff the hum out.
Oct 20, 2015, 11:05 AM
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Originally Posted by Tom T View Post
Try turning down the black and color brightness of the OSD. I forget exactly which one was doing it on mine as its been a while since I had the hum. Also, does your vtx have a left and right audio out? Try tying them together (make them into a mono source) as one may be emitting an audio signal that is getting picked up some how. Ive read that you can also ground one side (left or right) output of the vtx to snuff the hum out.
Thanks for the tips

Yeah, I had justed discovered that the osd black level tip was in the vector manual.. i would never have guessed that could be related.. (actually RMRC pointed this out minutes ago )

I'll play with that tonight..

The RMRC does have Left and Right audio on the tx audio out (i think).. i guess i'd have to figure out which are the audio lines and solder them together basically?

Alternative test would be to rule out the OSD.. might sound dumb but i'm not sure how i "bypass" and not use the OSD to test, while still sending a signal from both the camera and the tx to the rx (i think requiring a different cable that i may not have, will have to check).
Oct 20, 2015, 11:55 AM
Registered User
There is only 1 audio line on the RMRC 800mW
Oct 20, 2015, 12:08 PM
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Originally Posted by fpvbasher View Post
There is only 1 audio line on the RMRC 800mW

Ah ok, i dont know why i thought there might have been two..

That rules that out..

One other thing i did do that may be coming into play or not.. was that i cut the JST power connector from the harness (at least i think i did).. it gets power from the video or audio connectors on the vector.. perhaps this needed to be modded in some other way to prevent interference..

Then there is the potential since i'm testing inside thats its just 60hz interference (sounds like 60hz buzz). Taking it outside would eliminate that possibility.

Simplest check too is still the OSD black level change or if i had another harness, by passing the osd and see if the buzz continues.
Oct 20, 2015, 12:13 PM
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Mr.RC-CAM's Avatar
Quote:
If you unplug the camera, the sound goes away..
If removing the camera results in quiet audio then you have Video Vertical Sync bleeding into the audio. This can occur if the video signal levels are incorrect (due to vTx/vRx or OSD). 900MHz-1.3GHz systems are prone to this because their audio sub-carrier is very close to the video carrier. It rarely occurs on 2.4GHz-5.8GHz systems because they have additional separation of the audio & video carriers.

Quote:
Yeah, I had justed discovered that the osd black level tip was in the vector manual.. i would never have guessed that could be related
If the OSD's video levels are incorrect then the sync bleeding problem can occur. So start there.

- Thomas
Oct 20, 2015, 09:36 PM
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Quote:
Originally Posted by Mr.RC-CAM View Post
If removing the camera results in quiet audio then you have Video Vertical Sync bleeding into the audio. This can occur if the video signal levels are incorrect (due to vTx/vRx or OSD). 900MHz-1.3GHz systems are prone to this because their audio sub-carrier is very close to the video carrier. It rarely occurs on 2.4GHz-5.8GHz systems because they have additional separation of the audio & video carriers.


If the OSD's video levels are incorrect then the sync bleeding problem can occur. So start there.

- Thomas
I tried two things.. i powered the transmitter (video) and took the vector out of the equation.. no hum..

I then plugged it all back into the vector.. i tried changing the OSD black level setting from a 2 to a 3.. the hum became less.. also, lowering the color intensity to a 25 seemed to help.. setting the black level to 3 was too washed out to read the text.. so at this point its just been "slightly" minimized.
Oct 21, 2015, 11:04 AM
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I've also read that putting a 2200pf or 0.022uf 1kv capacitor (hard to find online at least via amazon?) may do the trick.. putting it across the ground to signal on the video tx cable.. may reduce picture sharpness though..

People have used the nte 90222 1kv (1000v) capacitor (ceramic disc).. i've seen a few labeled "radial", unsure of the difference.
Oct 21, 2015, 06:49 PM
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I was able to rig up cables to plug from the lcd directly into the vtx and vtx audio ports on the vector.. rather than using the 1.3 rmrc 800mw transmitter cables..

I get Zero noise when doing this..

I tried the negative terminal to touch the side of the RMRC transmitter or to the antenna ring, neither worked when testing transmitter mode..

Unsure what this implies, i guess it implies an issue with the transmitter, though when i bypassed the vector with just the transmitter cables, i did not get noise.
Last edited by markm75; Oct 21, 2015 at 06:54 PM.
Oct 21, 2015, 08:29 PM
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Mr.RC-CAM's Avatar
Quote:
Unsure what this implies, i guess it implies an issue with the transmitter, though when i bypassed the vector with just the transmitter cables, i did not get noise.
You should continue experimenting with various combinations of the OSD's video settings. There are about a dozen different parameters and they can interact, so finding the right combination can be a tedious adventure. For example, experiment with OSD parameters like these:
White & Black Levels (2 settings)
Color Intensities (5 settings)
Color Brightness (1 settings)
Color Hues (3 settings)
etc ...

Some vTx/VRx systems have poor immunity to sync bleeding. So worst case may require replacing those two things with a different pair. Ask your vTx/vRx supplier for help, they may have a solution.

- Thomas
Oct 21, 2015, 08:40 PM
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Daemon's Avatar
Or try this. Enable the Vector setting that allows you to toggle the mode switch to turn the OSD
display off completely (OSD Setup - Display Hardware Settings - Display On/Off with Mode
Toggle). Does it only hum when the OSD is displaying text, or not?
I may be wrong, but I doubt any of the settings above apply to anything other than the OSD
text overlay.
Oct 21, 2015, 09:02 PM
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Mr.RC-CAM's Avatar
The settings affect both text and graphics (page 57 of the Vector manual). The audio bleeding usually decreases as text or graphic items are removed from the OSD screen's layout. With that in mind, if there are unnecessary telemetry data items on the screen then disable them.

Although the Vector will continue to display the text/graphic data without a camera connected, adjustments to the video will be invalid without it. So when you adjust the menu's video parameters you must have the FPV camera installed on the Vector.

- Thomas
Oct 22, 2015, 10:57 AM
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markm75's Avatar
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Quote:
Originally Posted by Daemon View Post
Or try this. Enable the Vector setting that allows you to toggle the mode switch to turn the OSD
display off completely (OSD Setup - Display Hardware Settings - Display On/Off with Mode
Toggle). Does it only hum when the OSD is displaying text, or not?
I may be wrong, but I doubt any of the settings above apply to anything other than the OSD
text overlay.
Turning off the OSD resulted in a drastic drop in background buzz.. not completely gone but it did certainly reduce it..

I guess this still implies the transmitter and bleeding issues and or wiring internally thats not solid on the tx.

I have my 5.8 repeater (only 25mw though) and immersionrc receiver on hand.. i was going to try using those as the tx and see if the issue persists.


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