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Use of Ferrite Cores & RFI

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s(at)vestuti.orangehome.c
Guest

Posted: Wed Nov 26, 2008 11:35 am Post subject: Use of Ferrite Cores & RFI

Hi, I seem to be getting an increase in RF Interference on transmit since fitting the Airmaster  AP337 Prop. & AC200 Controller, has anyone fitted or experimented with Ferrite Cores on the cabling to reduce this or, should i be looking elswhere? Receive is fine,



Steve #573  G-CEBV

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ward.t(at)xtra.co.nz
Guest

Posted: Wed Nov 26, 2008 12:24 pm Post subject: Use of Ferrite Cores & RFI

Steve,

Martin, from Airmaster, told me to 'ground wire'   the base of the  AC 200 

controller  unit somewhere. Worked with my one.



Cheers,



Tim



Tim Ward

12 Waiwetu Street

Fendalton,

Christchurch

NEW ZEALAND

PH 0064 3 3515166

MOB 021 0640221

ward.t(at)xtra.co.nz

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s(at)vestuti.orangehome.c
Guest

Posted: Wed Nov 26, 2008 12:42 pm Post subject: Use of Ferrite Cores & RFI

Tim,

Do i still use the power conector ground or cut it, and use the new casing ground cable?



Steve #573 G-CEBV

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ward.t(at)xtra.co.nz
Guest

Posted: Wed Nov 26, 2008 12:51 pm Post subject: Use of Ferrite Cores & RFI

Steve,

No don't cut the earth. Just earth the base of the unit.

Tim

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budyerly(at)msn.com
Guest

Posted: Wed Nov 26, 2008 3:02 pm Post subject: Use of Ferrite Cores & RFI

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  Steve,

 I don't use the ferrite cores anymore.  Sorry.

 I have found that any Integrated Circuit device in an instrument panel  running near the coax antenna cables or your com leads is suspect.

 I learned my lessons with the Blue Mountain and the early video display  EFIS units.

 Those of us who have chased noise before have learned to do the  following:

  

 Shield any com wire or com component completely with the shields of all com  leads grounded together at the radio exactly as the manufacturer calls  for.  Those convenient grounds for Com Low or PTT can cause  trouble. 

  

 Do not run any component with a voltage regulator or IC circuit or  their in/outputs parallel with com wires or radio back without shielding or  ample separation.  

  

 That includes the Airmaster controller.  I would suspect the  power/ground wires may be near a com lead.  You may need to shield the  power wires but I doubt it.  Try a simple shield ground to the case on  an Airmaster controller as a start.  That will tell you who the culprit is  and may even do the trick.

  

 I've never had the Airmaster cause noise I could hear, but I've always  practiced the above.  Check that you haven't re-arranged other wires when  installing the Airmaster controller which would make a here to for unknown  problem rear its head.

  

 Good Luck, You'll enjoy the prop.

  

 Bud Yerly

 Custom Flight Creations

  

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rampil

Joined: 04 May 2007
Posts: 870

Posted: Wed Nov 26, 2008 4:36 pm Post subject: Re: Use of Ferrite Cores & RFI

Do you still have RFI when you pull the breaker on the Prop Control?

Do you have noise when the engine is off?

Do you have noise when the prop is changing pitch?

Respectively these circumstances could implicate the control box,

the brush plate, or the pitch motor.



If you really want diagnostic help, then it would be helpful to provide a useful amount of information.



Bud: Ferrite beads and cores have been tremendously oversold as a 

panacea, but for specific applications and circumstances they are champs.

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_________________
Ira N224XS

budyerly(at)msn.com
Guest

Posted: Thu Nov 27, 2008 5:57 am Post subject: Use of Ferrite Cores & RFI

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  You are right Ira, 

 The usual culprits though are the amateur wiring mistakes we all  make.  Ferrite cores are a band-aid.  Remember the problems with the  Gen 1 Blue Mountain, and the horrible comments from the field.  When I  rewired the panel and properly shielded the BM inputs and outputs, and made  sure the bundles were clear of the back of the Becker radios, all problems  ceased.  Too bad the problems inside the box didn't.

  

 Steve,

 Noise is best chased through a slow and meticulous chasing of each  component in the panel.

 That is why I have a bench, complete with com and engine sensor testing  leads to insure all my mistakes are made on the bench, not once the panel is in  the plane.  (Another reason I make the panels with cannon plugs is to make  install and uninstall quick and easy for just this reason.  It is an  airplane, if you don't put it together and take it apart at least 5 times you're  doing it wrong.)  That aside, other forms of noise you don't anticipate can  creep up.

  

 Along with what Ira wrote, do watch that the power bundle from the  alternator (if equipped) or Dynamo wiring is not parallel with the Airmaster  Wires.  They become antennas that way without proper shielding.  Check  alternator on off and every component in the panel.

  

 There is no replacement for good sound troubleshooting and careful  craftsmanship.

  

 Happy Building

 Bud Yerly

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s(at)vestuti.orangehome.c
Guest

Posted: Fri Nov 28, 2008 11:18 am Post subject: Use of Ferrite Cores & RFI

Hi,

I today sat in the europa with a hand held , engine running - & non 

running, and varius circuit breaker configurations,

it appears that i have been to quick to blame the Airmaster Prop., 

the interference seems to be coming from the ignition /mags - the 

right mag emitting more interference than the left. the "buzzing" is 

in frequency with engine RPM.

I recall that at the time of fitting the Airmaster i may have "coiled" 

the excess mag. cables.

The shielded mag. cables are only grounded at the key switch end, 

i will uncoil the two mag. cables next but what else can be done to 

reduce ignition interference? - what about the "twisted pair" method?



thanks to all the overseas builders for your feedback,



steve #573 G-CEBV

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