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Old Aug 13, 2012, 01:39 PM
Balsa&Tissue
payne9999's Avatar
United States, OR, Beaverton
Joined Jan 2011
2,794 Posts
Question
Servos: Long Leads cause interference?

I am building a 98" Dragon express. I really don't like using long linkages and bellcranks for the ailerons as shown on the plans. I would like to mount a servo near the aileron with a simple short link. I did this on a large DC-6 and I have not had any problems so far.

In the instructions it says not to do this because the long servo leads may pick up interference from the power systems. These instructions were written in the days of brushed motors when brush-less were fairly new. I will be running some brush-less 480 size motors with 20 amp ESC's for each motor.

Is interference really a concern on this setup?

Thanks,

Dave
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Old Aug 13, 2012, 06:31 PM
Aka: Tom Jenkins
ApexAero's Avatar
Palm Beach County, Fl.
Joined Aug 2008
4,508 Posts
From experience my suggestion is to do what is called the Poor Mans Choke. The article was written in the AMA mag like 20 yrs ago. Simply tie a square knot close to the Rx, yup a one loop knot. I used the tried and not so trustworthy Electron 6 on a 9C FM in a mini Helli, until I read the mag I had probs out the ying yang. Tied a knot on each servo lead and viola man. Of course I use Spectrum X now and don't worry about a thing. Some of the large scale guys use a match box that supplies the power off another supply etc. Longer wires and or heavier use think about HV servos and such.
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Old Aug 14, 2012, 04:31 AM
Registered User
Moss, Norway
Joined Jul 2003
439 Posts
Dave,

Are you using a 2.4 GHz radio system?
If so, don't worry, case closed.

If you are using a 72 MHz system, (35 MHz for us Europeans) then concerns/warnings etc. written 20 years ago still apply.

Regards,
Magne
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Old Aug 14, 2012, 04:44 AM
Registered User
Boomerang1's Avatar
Sydney Australia
Joined Mar 2005
924 Posts
I have a 110 inch B-36 with long leads out to the aileron servos .

It uses brushed 400 size motors & flys on a 36 Mhz system.

It's about 15 years old & I haven't had any problems yet! - John.
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Old Aug 14, 2012, 05:11 AM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
13,781 Posts
For long extension leads, I prefer to buy (or make), the ones with twisted wires, not the flat three wire strip. The 'twisted pair' principle, ( only a triple).
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Old Aug 14, 2012, 01:08 PM
Balsa&Tissue
payne9999's Avatar
United States, OR, Beaverton
Joined Jan 2011
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Thanks everyone.

I am using 2.4 gig Spektrum equipment and I didn't think it would be a problem but I saw the warning in the instructions. It probably was pre-2.4 gig information.

Dave
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Old Aug 15, 2012, 09:48 PM
Mulit-Platform Pilot
barracudahockey's Avatar
United States, FL, Jacksonville
Joined Sep 2004
3,490 Posts
Quote:
Originally Posted by eflightray View Post
For long extension leads, I prefer to buy (or make), the ones with twisted wires, not the flat three wire strip. The 'twisted pair' principle, ( only a triple).
The twisted pair prinicpal only applies when there's pairs.

Twisting servo wire has no benefit, and just makes the actual wire run longer.
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Old Aug 16, 2012, 06:14 AM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
13,781 Posts
But pairs of what ?.

There is a +ive, -ive, and a signal wire in the twist, are you saying only two signal wires benefit from the 'twisted pair' ?.
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Old Aug 16, 2012, 07:37 AM
Mulit-Platform Pilot
barracudahockey's Avatar
United States, FL, Jacksonville
Joined Sep 2004
3,490 Posts
Thats what I'm saying. More precisely, multiple pairs. Twisting the pairs prevents cross talk from adjacent pairs.

If you were to cut the sheath off a Cat 5 network cable and carefully examined it you would notice that each of the 4 pairs is twisted at a different rate of twists per inch so that the fields around each pair are not in phase. (simplified explanation)
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