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Help with radio intereference

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andrew.mcmenamin(at)xtra.
Guest

Posted: Sat May 03, 2008 10:38 pm Post subject: Help with radio intereference

I hope someone can help me!   I have little technical knowledge and may have some of the technical terms incorrect but would appreciate any advice.   

   

I fly a Skyranger with a Simonini engine, at a controlled airfield.  The Simonini is an Italian two cylinder, two stroke liquid cooled engine with dual Ducati ignition; two plugs per cylinder.  It performs best at over 5000 rpm.  I have significant problems with noise on the radio.  I have a microair radio and a DRE 4000 headset.   The radio is beautifully clear on the ground with the engine not running.   After start up, I get an RPM – related interference which makes the radio very hard to hear over 5000 rpm – i.e. at cruise.   I am also told the Tower find it hard to hear me.  I can overcome it by reducing RPM to 4000 before transmitting but this is not desirable!.  

   

The interference reduces noticeably as I cut each magneto in turn at the full power ground run up (when listening to the ATIS).  This makes me think it is ignition related.  

   

The spark plugs are NGK resistor plugs.  The plug caps are standard, no resistor and non-shielded.   The HT cables are NGK “racing” – i.e. copper core, no apparent shielding.  

   

The radio is positioned beside the two magneto switches on the dash, and shielded by the aluminium firewall from the mags.  It is not shielded from the mag switch wires.    

   

I suspect the problem is to do with the HT cables, or the plug caps, or possibly the wires to the mag switches.   I have read that I should not use resistor caps when already using resistor plugs.   Should I use different HT leads??  

   

Andrew   

   

   

   

   

        [quote][b]

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reichec

Joined: 23 Apr 2007
Posts: 26

Posted: Sun May 04, 2008 3:20 am Post subject: Help with radio intereference

I would start with trying to shield the plug wires  first, also you should have shielded p lead wires goign to your switch grounding  the shield at both ends.  also check that your antenna base is well  grounded thru the screws into the airframe and that belly oil or other gunk  hasnt gotten underneath the antenna mounting,  seal those antennas with a  good sealant like pro-seal or fuel sealant for a long life seal, I also  throw some whitesilicone over the screw heads if the antenna is the thru  hole mounting style.

  

 Good luck with what sounds like a non typical  flying contraption!

 safe flying!

 Charles

  

 [quote]   ---

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romott(at)mi-connection.c
Guest

Posted: Sun May 04, 2008 4:39 am Post subject: Help with radio intereference

I would try replacing the solid wire HT.  I have a noise problems with my 

electronic ignition system - Jeff Rose Electroair on my Velocity.



In my research into the problem, the resistance wire used with high energy 

ignition systems is key to reducing ignition noise. I tried to find the 

article that I had saved - but can't find it right now.  Interestingly 

enough, I have a Garmin 430 and a Microair 760.  Guess what, the cheap radio 

doesn't pick up the noise - it is the high dollar Garmin 430.  Turning off 

the Electroair makes the noise go away.

 	  Quote: 	
		   Time: 11:38:36 PM PST US

 From: "Andrew McMenamin" <andrew.mcmenamin(at)xtra.co.nz>

 Subject: Help with radio intereference



 I hope someone can help me!   I have little technical knowledge and may 

 have

 some of the technical terms incorrect but would appreciate any advice.

 I fly a Skyranger with a Simonini engine, at a controlled airfield.  The

 Simonini is an Italian two cylinder, two stroke liquid cooled engine with

 dual Ducati ignition; two plugs per cylinder.  It performs best at over 

 5000

 rpm.  I have significant problems with noise on the radio.  I have a

 microair radio and a DRE 4000 headset.   The radio is beautifully clear on

 the ground with the engine not running.   After start up, I get an RPM -

 related interference which makes the radio very hard to hear over 5000 

 rpm -

 i.e. at cruise.   I am also told the Tower find it hard to hear me.  I can

 overcome it by reducing RPM to 4000 before transmitting but this is not

 desirable!.

 The interference reduces noticeably as I cut each magneto in turn at the

 full power ground run up (when listening to the ATIS).  This makes me 

 think

 it is ignition related.

 The spark plugs are NGK resistor plugs.  The plug caps are standard, no

 resistor and non-shielded.   The HT cables are NGK "racing" - i.e. copper

 core, no apparent shielding.

 The radio is positioned beside the two magneto switches on the dash, and

 shielded by the aluminium firewall from the mags.  It is not shielded from

 the mag switch wires.

 I suspect the problem is to do with the HT cables, or the plug caps, or

 possibly the wires to the mag switches.   I have read that I should not 

 use

 resistor caps when already using resistor plugs.   Should I use different 

 HT

 leads??

 Andrew

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Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun May 04, 2008 4:48 am Post subject: Help with radio intereference

Sounds like the same type of ignition they put on the Rotax 582.  That engine uses both resistor plugs and resistor plug caps  (5k plugs BR8ES and 5K resistor caps.)  Btw they recommend you only buy solid core plugs, not the ones with the screw on terminal.  The solid core plugs have a stronger heavies top than the aluminium screw on clip.  The general rule of thumb is to use either resistor plugs or resistor caps... The Duc ignition seems to be the exception that makes the rule.  

   

It that doesn’t work. You can then try looking at shielding your spark plugs or installing an antenna a bit more distant from the engine...  I’ll go out on a limb here and bet one full bubblegum the resistor plugs and resistor caps will do the trick.  Any takers J  

   

Noel  

       

From: owner-avionics-list-server(at)matronics.com [mailto:owner-avionics-list-server(at)matronics.com] On Behalf Of Andrew McMenamin

 Sent: Sunday, May 04, 2008 4:06 AM

 To: avionics-list(at)matronics.com

 Subject: Help with radio intereference  

  

  

   

I hope someone can help me!   I have little technical knowledge and may have some of the technical terms incorrect but would appreciate any advice.   

   

I fly a Skyranger with a Simonini engine, at a controlled airfield.  The Simonini is an Italian two cylinder, two stroke liquid cooled engine with dual Ducati ignition; two plugs per cylinder.  It performs best at over 5000 rpm.  I have significant problems with noise on the radio.  I have a microair radio and a DRE 4000 headset.   The radio is beautifully clear on the ground with the engine not running.   After start up, I get an RPM – related interference which makes the radio very hard to hear over 5000 rpm – i.e. at cruise.   I am also told the Tower find it hard to hear me.  I can overcome it by reducing RPM to 4000 before transmitting but this is not desirable!.  

   

The interference reduces noticeably as I cut each magneto in turn at the full power ground run up (when listening to the ATIS).  This makes me think it is ignition related.  

   

The spark plugs are NGK resistor plugs.  The plug caps are standard, no resistor and non-shielded.   The HT cables are NGK “racing” – i.e. copper core, no apparent shielding.  

   

The radio is positioned beside the two magneto switches on the dash, and shielded by the aluminium firewall from the mags.  It is not shielded from the mag switch wires.    

   

I suspect the problem is to do with the HT cables, or the plug caps, or possibly the wires to the mag switches.   I have read that I should not use resistor caps when already using resistor plugs.   Should I use different HT leads??  

   

Andrew   

   

   

   

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       [quote][b]

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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun May 04, 2008 5:08 am Post subject: Help with radio intereference

Shielding the P leads is a good idea.  It should be part of the original installation, but... only shield them at one end, where the ground should be strongest.  Typically this will be the engine end however some switches have grounded cases at which time the shield should be grounded at the switch end.  Shields should NEVER be grounded at both ends because if there is a difference in the strength of the ground from one end to the other (there will be) you have just constructed a capacitive couple to make the interference worse.  

   

Noel  

       

From: owner-avionics-list-server(at)matronics.com [mailto:owner-avionics-list-server(at)matronics.com] On Behalf Of Charles Reiche

 Sent: Sunday, May 04, 2008 8:43 AM

 To: avionics-list(at)matronics.com

 Subject: Re: Help with radio intereference  

  

  

     

I would start with trying to shield the plug wires first, also you should have shielded p lead wires goign to your switch grounding the shield at both ends.  also check that your antenna base is well grounded thru the screws into the airframe and that belly oil or other gunk hasnt gotten underneath the antenna mounting,  seal those antennas with a good sealant like pro-seal or fuel sealant for a long life seal, I also throw some whitesilicone over the screw heads if the antenna is the thru hole mounting style.  

    

   

    

Good luck with what sounds like a non typical flying contraption!  

    

safe flying!  

    

Charles  

    

   

   	  Quote: 	
		      

----- Original Message -----   

    

From: Andrew McMenamin (andrew.mcmenamin(at)xtra.co.nz)   

    

To: avionics-list(at)matronics.com (avionics-list(at)matronics.com)   

    

Sent: Sunday, May 04, 2008 2:35 AM  

    

Subject: Help with radio intereference  

    

   

  

I hope someone can help me!   I have little technical knowledge and may have some of the technical terms incorrect but would appreciate any advice.   

   

I fly a Skyranger with a Simonini engine, at a controlled airfield.  The Simonini is an Italian two cylinder, two stroke liquid cooled engine with dual Ducati ignition; two plugs per cylinder.  It performs best at over 5000 rpm.  I have significant problems with noise on the radio.  I have a microair radio and a DRE 4000 headset.   The radio is beautifully clear on the ground with the engine not running.   After start up, I get an RPM – related interference which makes the radio very hard to hear over 5000 rpm – i.e. at cruise.   I am also told the Tower find it hard to hear me.  I can overcome it by reducing RPM to 4000 before transmitting but this is not desirable!.  

   

The interference reduces noticeably as I cut each magneto in turn at the full power ground run up (when listening to the ATIS).  This makes me think it is ignition related.  

   

The spark plugs are NGK resistor plugs.  The plug caps are standard, no resistor and non-shielded.   The HT cables are NGK “racing” – i.e. copper core, no apparent shielding.  

   

The radio is positioned beside the two magneto switches on the dash, and shielded by the aluminium firewall from the mags.  It is not shielded from the mag switch wires.    

   

I suspect the problem is to do with the HT cables, or the plug caps, or possibly the wires to the mag switches.   I have read that I should not use resistor caps when already using resistor plugs.   Should I use different HT leads??  

   

Andrew   

   

   

   

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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

jetboy

Joined: 22 Jul 2006
Posts: 233

Posted: Sun May 04, 2008 9:12 pm Post subject: Re: Help with radio intereference

Its going to be difficult to properly shield the wires. NGK used to sell shielded plugs in their range I understand are not available now. 



I had bad radio noise on a Jabiru installation and did some RFI testing of various types of HT lead, shielding and R plugs.



Changing from carbon HT leads to inductive resistive wire yielded the best improvement. The brand I used was Bosch so if not available something from NGK, Denso or Magnecore might be similar. Aircraft shielded harness wire was little better than plain copper. Resistor plugs helped, but using extra resistor caps would be unwise. 



 If your HT leads from the coil packs are not replaceable, slip a small ferrite clip-on supression bead at the coil ends, and another midway. These are obtainable from electronics stores and normally used on audio and computer cabling. I did this on my coil leads as they are copper, and it helped.



The other method is to shift the radio antenna as far away as practical from the engine.



Ralph

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