Why does my video break up?

The symptom

The picture in your goggles is not clean. It might be snow, rolling bars and colour dropping out; it might be blocky squares, a freeze, then black. It might be perfect at the takeoff spot and rubbish two hundred metres out, or rubbish everywhere and fine on the bench.

The first thing to understand is that analogue and digital do not break in the same way, and the difference is diagnostic in itself.

Analogue degrades gracefully. As the link weakens you get static, snow, rolling lines, loss of colour, and finally a rolling grey mess. It gets steadily worse as the margin shrinks. That is not a defect — it is the single most useful property analogue has. The picture is a live signal-strength meter, and it warns you before it fails.

Digital degrades as blocking, freezing, and then a cliff. It stays flawless right up to the point where it does not, and then it is gone completely, often with no more than a second or two of blocking to tell you it was coming. The absence of warning is the danger. If you have moved from analogue to digital and you are flying the same distances with the same confidence, you are flying with a broken warning light.

Whichever system you have, the fault beneath the symptom is almost always the same short list.

Check this in 60 seconds

Do not change a setting. Answer three questions, and you will have narrowed it to one category.

1. Does it get worse with distance? If the picture is clean near you and degrades as you fly out, it is the RF link: antennas, range, obstruction, interference. This is the overwhelming majority of cases.
2. Does it get worse with throttle? If lines, bars or rolling appear when you punch out and clear when you idle, it is power and noise on the VTX supply. That signature — noise that pulses in time with the throttle — is close to conclusive on its own.
3. Does it get worse when you touch the aircraft or when it vibrates? Wiggle the camera lead, the VTX lead, the antenna connector, with the picture live on the bench. If the picture breaks when you handle it, it is a wire, not a radio. Stop looking at your channel plan.

Distance, throttle, touch. Almost every video fault is one of those three.

1. Antennas — this is your problem

It is the antenna. It is nearly always the antenna, and everything else on this list is a distant second.

Damage. Coax that has been crushed, kinked, bent hard at the connector, or had the shielding pierced in a crash. The antenna looks fine from a metre away and radiates almost nothing.

Transmitting into an unplugged antenna. Power up a VTX with no antenna fitted, or with one that has worked loose, and the transmit power has nowhere to go. It reflects back into the output stage and can destroy the VTX outright, in seconds. This is the most expensive beginner mistake in FPV, and it is entirely avoidable: never apply power to an aircraft without checking the antenna is fitted and tight. Make it part of the same reflex as checking props.

Wrong or mismatched polarisation. A circular-polarised antenna talking to a linear one, or right-hand talking to left-hand, throws away a large fraction of your link for no reason at all. Both ends must agree.

Mounting and shadowing. The airframe is made of carbon, and carbon is opaque to your video signal. A battery is a dense lump of metal. If the antenna sits behind the frame, behind the battery, or below the arms, then whenever the aircraft is between the antenna and your face — which is exactly what happens when you fly away from yourself — the signal has to get through the aircraft. Mount the antenna where it can see you: up, clear of the frame, clear of the pack.

Orientation and the null. An antenna does not radiate equally in all directions. A dipole radiates in a doughnut around its length, and there is a deep null directly off the tip. Fly straight away from yourself, at the same altitude, with the antenna standing vertically, and you are pointing the weakest part of the pattern at your goggles. This is why the picture sometimes dies at moderate range in level, straight-out flight and comes back the moment you turn or climb. It is not a fault. It is geometry.

2. Range and obstruction

Line of sight is not a metaphor. At these frequencies, a tree line, a building, a hill, or the curve of the ground between you and the aircraft will take your picture apart. So will your own body — turning your back on the aircraft puts several kilograms of water between the transmitter and the receiver.

Get high, get clear, and keep the aircraft in sight. If the picture only breaks up when the quad goes behind the barn, you have diagnosed it.

3. Power and noise on the VTX supply

A VTX fed from a noisy rail puts that noise straight into the picture: horizontal bars or lines that shift, roll, or pulse in time with the throttle. That signature is diagnostic. Nothing else does it.

This is a wiring and filtering problem, not a radio problem. Feed the VTX from a clean, filtered supply — a proper regulator rather than a raw, ESC-shared rail — keep the video wiring away from the motor leads, and make sure the aircraft has adequate capacitance on the power input. If you have removed the capacitor because it looked untidy, that was a mistake.

4. Interference

Someone else on an overlapping channel will wreck both of your pictures. So will your own aircraft. A high-power VTX sitting centimetres from the RC receiver or the GPS module can desensitise them — which shows up as control-link and GPS trouble rather than video trouble, but it is the same cause. And a 2.4 GHz control link sitting next to a 2.4 GHz video system is asking two radios to share a room.

Separate the antennas. Put distance between the VTX and everything that listens.

5. Heat

A VTX run at high power with no airflow will overheat, and a hot VTX degrades before it shuts down — so the picture gets worse before it disappears. Never transmit at high power on the bench without props spinning or a fan on it. If your video is clean in the air and falls apart while you sit there doing setup on the ground, this is why.

6. Camera and wiring faults

A broken or fraying camera lead produces intermittent, full-frame dropouts that have nothing to do with distance. Black frames, sudden total loss, back to normal. If the aircraft is on the bench, two metres from you, and the picture still cuts out, no antenna in the world will fix it.

Wiggle test. Live picture, hands on the aircraft, work along every video wire and connector. If you can provoke it, you have found it.

7. Ground-side problems

You are half the link, and you are the half nobody checks. A damaged goggle antenna. A receiver module not fully seated in its bay. A diversity module quietly selecting the wrong antenna, or one input dead so diversity has nothing to choose from. Swap antennas between goggle inputs and see whether the fault follows the antenna or stays with the socket.

How to know you actually fixed it

Not "it looked better on the last pack."

• The fault no longer reproduces under the condition that caused it. If it was distance, fly the same line, to the same place. If it was throttle, punch out on the bench and watch for the bars. If it was a wire, wiggle it.
• Fly the same route twice. A video fault that comes back on the second pack was never fixed.
• On digital especially, judge the link by its margin, not by the picture — because the picture will happily tell you everything is perfect right until the cliff.

Last thing

Video breakup feels like a mysterious, atmospheric problem, and it almost never is. It is a bent coax, a battery in front of an antenna, a dirty rail, or a wire that has been flexing since your last crash. Work the three questions — distance, throttle, touch — and check the antenna first, because it is the antenna.