Fpv Video Feed Goes Black and Comes Back

In this article I will share some tips on how to fix issues and best practices to follow to avoid FPV video problems. Interference and noise in your FPV video feed can be a major headache, and some issues with your VTX can even affect other people you are flying with.

Ta2ble of Content

• How to power VTX and Camera
• LiPo is noisy
• Every ground pin is different
• Signal ground
• White lines
• Black lines
• Connect camera to VTX directly
• LC Filter
• Jello

Best Way to Power VTX and Camera

First things first, you have to ascertain what voltage your FPV camera is capable of receiving. Most FPV cameras these days have a wide operating voltage often from 5V to 30V or even higher.

The safest way to power your FPV camera is from the VTX. Many VTX's these days have a filtered 5V output dedicated for powering FPV cameras. Even if you are already using a filtered power source for your VTX, we still recommend using the filtered output from the VTX for the camera, any additional filtering is better.

If your can't power the FPV camera directly from the VTX for any reason, the next best thing is to power both VTX and camera from the same filtered and regulated power source.

Most noise related issues are caused by powering either the FPV camera or VTX, or both, directly from the main LiPo battery.

Power Directly from LiPo is Noisy

As mentioned, the majority of FPV cameras and VTX's these days can be powered directly from a 4S or even 6S LiPo battery. However, just because you can, it doesn't mean you should.

Any video device likes a stable power source so it can transmit a nice clean image. The constant fluctuating power conditions that are brought about by the ESC's and motors make the raw voltage from a LiPo battery noisy. This noise can pass through the PDB or flight controller to your VTX and FPV camera, subsequently manifesting as interference in your FPV goggles.

Most VTX's these days have some kind of power filtering, not only for their own circuitry but additionally for the 5V output. FPV cameras generally have little to no integrated filtering. To eliminate noise in your FPV video feed, you need the cleanest possible power for your camera and VTX, which is where capacitors come into play.

Where to Add Capacitors

Additional capacitors (or caps) are often used at the power input of a device to clean up the electrical noise. Theoretically a cap placed closest to the source of the noise is the most effective, hence pilots adding caps to individual ESC's on the arms of their quads.

How you are supplying power to your VTX will determine the best place to install a cap. If it's getting power from 5V then you should put the cap on the 5V rail, it's it's 12V then put the cap on the 12V rail. If it's powered directly from the LiPo, then put the cap on the XT60 pads.

I see a lot of people add capacitors at the XT60 pads regardless of how the VTX is being powered, this might help reduce the amount of noise in your power system generally, but may not be the most effective solution for your video.

Twisting Signal and Ground Wires

It is good practice to twist the video signal and ground wires together, this acts like a shield against induced external noise from ESC's and BEC inductors. Also keep the VTX signal and power wires away from any BEC inductors.

Keeping ESC aways from FC BEC

The MOSFET on your ESC can create interference that affects your FC, and if your camera and VTX are connected to it, you might get noisy video.

In this post I explained how to minimize noise from the ESC FET's getting to the FC with shielding.

Every Ground Pin Is Different

Ideally, all ground pins are the same, but in reality that's not necessarily true.

Ground pins are connected using a piece of wire or a copper trace on a PCB. Any piece of wire or copper trace has resistance, capacitance and inductance.

Because of this, there will be a voltage difference between two ground pins on a circuit board if there is current flowing through them. Think of this as an extremely tiny resistor.

This is why it's best practice to connect the grounds of your VTX and FPV camera to the same pin, or to two ground pins as close to each other as possible.

Signal Ground Is Important

There is current going through the power and signal wires, and eventually it has to return to its source via the ground wires. It's a complete cycle, that's why it's called a "circuit".

When you don't have signal ground connected, the signal can only return to its source through the power ground. Therefore the signal will be "more vulnerable" to the noise in the power. By having a signal ground, you can better "isolate" the signal from the power.

This is especially important when you are powering your FPV system directly from the main LiPo battery.

"White Lines" in Video?

"White lines" are usually a sign of excessive electrical noise in the power to either the FPV camera or VTX, or both. Adding a low ESR capacitor to the ESC power, or XT60 pads should usually fix it.

Further Reading: why and where to add low ESR capacitor in a mini quad?

When you are getting lines in your FPV video, try to fix your FPV setup's power first by powering your FPV camera from your VTX. If that doesn't work, try adding a capacitor.

"Black Lines" in Video?

"Black lines" are usually low power related, which are commonly caused by a power hungry VTX. Some VTX don't do well with stepped-down voltage, and they might struggle to deliver the desired output power.

If you are getting black lines in the video feed, you might find the issue to be worse at a higher output power such as 800mW than a lower power such as 25mw. If that's indeed the case then it's definitely related to insufficient power or voltage to the VTX.

You can try powering your VTX directly from the battery. If this does not solve the issue, you may have a defective VTX or camera.

Connecting FPV Camera to VTX Directly

Don't wire things you aren't using, such as OSD or camera control. Unnecessary wiring might introduce noise to your FPV system. If you are not using OSD, simply wire your camera's video output straight to your VTX and bypass the video signal pads on the FC.

Almost Last Resort

If you are getting some lines in your video, but none of the above helped, it could be the VTX or camera wires picking up noise from other components. This could be the reason if you run a long signal wires from the camera and VTX.

The solution is to use a "shielded wire" (mini coax wire) instead of normal silicone wire: https://amzn.to/2OjPaFo

LC Filter

Another solution to cleaner video feed is to use an LC filter between the power and your FPV system. They can be bought ready made, or you can DIY your own power filter.

It is good at targeting noise in the power getting to your FPV system, but it doesn't reduce the level of noise in the power like a low ESR capacitor does.

Check Antennas

Maybe your noise issue isn't related to power at all, many video problems can be traced back to antennas. Make sure both VTX and VRX antennas are both properly mounted, and that they are of the correct connector type, i.e. RP-SMA / SMA, and the correct polarization RHCP / LHCP. Another thing you can try is changing your channel, you could be picking up interference from an external source.

Flying with Others?

If you fly with others and there is interference, see this guide on how to select the best channels.

Jello on Well-Tuned Quad

Most FPV cameras these days have CMOS sensors, which means they are more prone to "jello" than CCD cameras. You should not have jello in your FPV video if your quad is well tuned and performing properly. If you do not hear noticeable oscillations from the quad, but there is jello, check the following:

• loose camera mount screws?
• loose camera lens – is the lens lock nut broken?
• loose camera sensor inside the camera?

If none of these is the cause, try using TPU mounts for the FPV camera. The flexible and soft material absorbs some of the vibrations.

Edit History

• Mar 2018 – Article created
• Apr 2019 – Updated
• Jul 2019 – added "where to add cap" and "twisting signal/ground wires"
• Sep 2019 – added info about "ESC shielding" and matching antennas
• Dec 2019 – Revised

bradleyhimantand.blogspot.com

Source: https://oscarliang.com/connect-vtx-fpv-camera/