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Old Jan 05, 2008, 11:11 PM
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Valencia, CA
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Glitch Free Installatiions - FPV Wiring Best Practices to Reduce Interference

What are the best practices to avoid interference when using components for FPV?

For instance, there are threads that say you should twist your wires... Does this help? Do you twist all wires such as servo wires, video tx wires, micro cam wires, etc??? Threads here also state you should separate the wires before you twist them... What does this do?

Next, Ferrite clips/rings. Are these effective? For instance, if I have a 36" servo extension and I clip a Ferrite clip/ring to ONLY ONE end of the servo wire, does that prevent interference for the whole length of the servo wire?

Please add all your experiences to this thread so we can put our heads together to get the best results for clear video and glitch free installations.
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Old Jan 05, 2008, 11:26 PM
jab
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One word.. SEPARATION. You'd be amazed how much video noise you can clear up just by separating the airplane electronics and video equipment by a couple of extra inches. Even helps increasing the R/C receiver range!
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Old Jan 06, 2008, 02:41 AM
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Mark Harris's Avatar
Perth, Western Australia
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Twisting the wires cancels out electromagnetic interference, must as twisted pair in CAT5/6 does.

The idea of separating the wires is so that they are able to twist together better and will hold their twist i believe. It's quite difficult to get a tight twist on 3 wires glued together, not so hard to get it on 3 separate wires.
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Old Jan 06, 2008, 04:14 AM
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Quote:
Originally Posted by Mark Harris
Twisting the wires cancels out electromagnetic interference, must as twisted pair in CAT5/6 does.
Mark
can you explain twisted pair in CAT5/6
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Old Jan 06, 2008, 04:33 AM
Zoom!
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Joined Aug 2006
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Any benefits to braiding as opposed to simply twisting? I'm about to put another TwinStar together specifically for FPV and I'd like to place the receiver way in the back, causing some pretty long extensions.

As for ferrite rings, what exactly does it do? What's the placement? Or is twisted wires enough?

Cheers!
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Old Jan 06, 2008, 05:30 AM
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Perth, Western Australia
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VRFlyer:
http://en.wikipedia.org/wiki/Twisted_pair

I'm a CCNA so we had to learn alllll about it. Very boring.

Finder, i just separate and twist. hold the servo in place and then just turn the wires until you end up with a really tight twist. Want it to look like this:


And as far as ferrite rings, my understanding is that they stop high frequency signals getting through, so you just get the servo pulse and not other crap that gets picked up. I'd put the ferrite on any digital servos, and ESC wires (especially ESC wire) and twist em all. more the merrier as far as things which improve signal quality.
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Old Jan 06, 2008, 05:38 AM
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Wikipedia has a nice article about twisted pair wires: http://en.wikipedia.org/wiki/Twisted_pair, which is also what the CAT5/6 reference is with regard to (http://en.wikipedia.org/wiki/CAT_5). Pulling some Cat 5 cable apart would be a cheap way to get machine twisted wire pairs, although its probably only good for fairly low current.
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Old Jan 06, 2008, 06:23 AM
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Canada, BC, Duncan
Joined Dec 2006
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Quote:
Originally Posted by VRflyer
Mark
can you explain twisted pair in CAT5/6
Cat5 has 8 wires, 2 are twisted together (Twisted Pairs) to make up 4 pairs. See illustration
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Old Jan 06, 2008, 01:01 PM
Tesla's Workshop
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Separation: Induced or Radiated RF
- Electromagnetic energy falls off at an inverse square of the distance. Double any distance and you have reduced the RFI by four times.
- VidTX and/or DataTX should be as far away from the RC antenna as possible.

Isolation: Conducted RF
- Use Opto isolated ESCs and linear regulators (yes, there are switching regulators out there that work; Intelligent Flight makes some). Linear regulators are less efficient but do not produce RFI the way a switching regulator might. I really like the Smart-Fly.com brand of linear regulators.
- Use a separate video battery and regulator to keep the RC system and video system isolated.
- Twist servo wires to cancel stay signals

Grounding:
- Avoid Ground Loops; common circuits should have a common negative ground.
- Add a ground plane (counterpoise). Adhesive backed copper foil can be added to the underside of a fuselage for a ground plane. This is usually not necessary for low power systems (<1W).

Quality: Component Selection
- One should use the best RC gear one can afford especially the RC receiver.
- Use layouts that have worked for others as a starting point for any project.

Jeff
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