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Ignition Noise

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georgerace

Joined: 25 Oct 2006
Posts: 788
Location: Albion, MI

Posted: Sat Aug 30, 2008 11:53 am Post subject: Ignition Noise

I am getting a lot  more ignition noise than I like in my Icom COM Radio.

  

 The noise is so bad  that most of the time it is opening the squelch on the radio and I am listening  to just noise!

  

 I read somewhere  that putting in resistor plugs may solve the problem.  I was looking at my  ignition wiring today and noticed that it say "noise suppression wire" or  something like that on the bright red plug and coil leads.  Would it still  be OK to add resistor plugs with the wire already being noise suppression  type?

  

 Anybody have any  other ideas that I could try?

  

  

   [quote][b]

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notsew_evets(at)frontiern
Guest

Posted: Sat Aug 30, 2008 12:34 pm Post subject: Ignition Noise

And,,,  if its actually engine noise you  should hear the mags frequency change with rpm...

 [quote]   ---

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notsew_evets(at)frontiern
Guest

Posted: Sat Aug 30, 2008 12:34 pm Post subject: Ignition Noise

George

 Not a professional but I have had this type of  noise in my past two homebuilts.

 First:  Do other radios "hear" your  transmissions clearly ?

 If yes,  yet there is noise in receive  only, I bet its because the radio wires are not shielded and or grounded on  one end......

 My first time it was that I didnt use shielded  wire.  I change out all wires to the shielded type.  Still had some  noise.  Then a real radio man told me to ground the shielded wire on one  end only.  Otherwise you get a looped circuit and that also causes  interference.....

 SW

 [quote]   ---

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bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Sat Aug 30, 2008 1:21 pm Post subject: Ignition Noise

Are you using this radio with an intercom wired into the plane? If so you should be using shielded wires for all your audio circuits. I would use two wire shielded wire for the audio output lines (audio LO, audio HI and shield) and three wire shielded wire for the microphone lines (audio LO, Audio HI, PTT and shield). Don't use the shield as part of the audio circuit, just as a shield. The audio signals should run through the wires enclosed by the shield. All the shields should be grounded at only one end, usually you would ground them all at the intercom or audio panel since they all travel through there anyway. Make sure the headset jacks aren't grounded, use plastic washers and grommets to isolate them from the chassis if necessary. B and C Specialty Products sells these isolation washers if you need them.



You might also need to use shielded wire for you magneto leads. These can and probably should be grounded at both ends since this shield is intended to keep noise from getting out of these wires rather than from getting in.

Using resistor plugs in addition to the noise suppression wire might give some additional benefit.



On Aug 30, 2008, at 3:52 PM, George Race wrote:

[quote]  I am getting a lot more ignition noise than I like in my Icom COM Radio.

  

 The noise is so bad that most of the time it is opening the squelch on the radio and I am listening to just noise!

  

 I read somewhere that putting in resistor plugs may solve the problem.  I was looking at my ignition wiring today and noticed that it say "noise suppression wire" or something like that on the bright red plug and coil leads.  Would it still be OK to add resistor plugs with the wire already being noise suppression type?

  

 Anybody have any other ideas that I could try?

  

 

[b]

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_________________
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Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

steerr(at)bellsouth.net
Guest

Posted: Sat Aug 30, 2008 1:34 pm Post subject: Ignition Noise

I agree with Bryan - use shielded wires.  I have a wiring diagram for my 

radio and intercom that I'd be happy to forward to anybody as an 

example.  It shows exactly what Bryan is talking - ground at only one point.



Bill

Bryan Martin wrote:

 	  Quote: 	
		   Are you using this radio with an intercom wired into the plane? If so 

 you should be using shielded wires for all your audio circuits. I 

 would use two wire shielded wire for the audio output lines (audio LO, 

 audio HI and shield) and three wire shielded wire for the microphone 

 lines (audio LO, Audio HI, PTT and shield). Don't use the shield as 

 part of the audio circuit, just as a shield. The audio signals should 

 run through the wires enclosed by the shield. All the shields should 

 be grounded at only one end, usually you would ground them all at the 

 intercom or audio panel since they all travel through there anyway. 

 Make sure the headset jacks aren't grounded, use plastic washers and 

 grommets to isolate them from the chassis if necessary. B and C 

 Specialty Products sells these isolation washers if you need them.

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davgray(at)sbcglobal.net
Guest

Posted: Sat Aug 30, 2008 3:02 pm Post subject: Ignition Noise

George

  I just had a problem where a linear voltage  regulator was injecting noise in a 4 inch unshielded area where the shielded  wire breaks out to the jacks.  It was bad design to even have these power  wires running thru this area.

  

 Gary

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