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Radio interference

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robintaylor

Joined: 25 Apr 2013
Posts: 7

Posted: Thu Apr 25, 2013 9:21 am Post subject: Radio interference

I am getting radio interference which seems to be from the alternator.

I am flight testing my homebuilt RV9A. It has a new Lycoming O320 engine which has a Plane Power AL12 alternator.

The interference is a pulse or beep at an interval of about two per second. Its interval changes with the engine speed and it ceases when the alternator is disabled.

Please can you suggest the cause and a solution.

RobinT

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Apr 25, 2013 4:14 pm Post subject: Radio interference

At 12:21 PM 4/25/2013, you wrote:

 	  Quote: 	
		  

<robintaylor(at)airteccc.co.uk>



I am getting radio interference which seems to be from the alternator.

I am flight testing my homebuilt RV9A. It has a new Lycoming O320 

engine which has a Plane Power AL12 alternator.

The interference is a pulse or beep at an interval of about two per 

second. Its interval changes with the engine speed and it ceases 

when the alternator is disabled.

Please can you suggest the cause and a solution.

RobinT 


	


  Does the noise get louder if you turn everything

  on and/or softer with everything but the radio

  off?



  Can you describe your ground system for us?

   Bob . . .

Builder_Bill

Joined: 19 Sep 2012
Posts: 7
Location: Newport News, VA USA

Posted: Sat Apr 27, 2013 11:05 am Post subject: Re: Radio interference

Hey Bob, if the noise gets worst at higher alt output, does that implicate a rectifier diode exclusively? I was trying to think if there was another source of noise that would follow the alt load.



Bill

robintaylor

Joined: 25 Apr 2013
Posts: 7

Posted: Thu May 02, 2013 4:25 am Post subject: Re: Radio interference

Thanks for the response Bob,

I had to wait until I flew again.

I am flying with twin Dynon Skyviews, as I turn each off, the noise progressively reduces.

The frequency of the noise increases with the speed of the engine.

I have a common ground on the firewall that everything is connected to.

nuckolls.bob(at)aeroelect
Guest

Posted: Thu May 02, 2013 4:58 pm Post subject: Radio interference

At 07:25 AM 5/2/2013, you wrote:

 	  Quote: 	
		  

<robintaylor(at)airteccc.co.uk>



Thanks for the response Bob,

I had to wait until I flew again.

I am flying with twin Dynon Skyviews, as I turn each off, the noise 

progressively reduces.

The frequency of the noise increases with the speed of the engine.

I have a common ground on the firewall that everything is connected to.


	


    Hmmmm . . . Do the Dynon units have audio outputs

    for annunciation/warning signals?

   Bob . . .

robintaylor

Joined: 25 Apr 2013
Posts: 7

Posted: Thu May 02, 2013 9:46 pm Post subject: Re: Radio interference

Yes, the Dynons do have an audio output.

Thanks,

Robin

nuckolls.bob(at)aeroelect
Guest

Posted: Fri May 03, 2013 5:22 am Post subject: Radio interference

At 12:46 AM 5/3/2013, you wrote:

 	  Quote: 	
		  

<robintaylor(at)airteccc.co.uk>



Yes, the Dynons do have an audio output.

Thanks,

Robin


	


  Okay, the first experiment is to disconnect these

  two signal sources and record the effect on the

  noise.

   Bob . . .

robintaylor

Joined: 25 Apr 2013
Posts: 7

Posted: Mon May 20, 2013 11:12 am Post subject: Re: Radio interference

Hi Bob,

I have disconnected the audio output from the Skyviews and the noise goes away.

Thanks,

Robin

sttwig

Joined: 26 Aug 2007
Posts: 31
Location: Yakima, WA

Posted: Mon May 20, 2013 11:37 am Post subject: Radio interference

Did you connect a ground wire to the case of the Skyview per their 

instructions toward the bottom of page 4-17: To minimize the possibility 

of audio “humming”, a 16 AWG wire may optionally be connected between 

the ground point for the intercom/audio panel/radio(s) and SkyView 

display case(s). To attach the wire to the SkyView display case, a 4-40 

x 3/16” long screw maybe be screwed into the threaded boss above the USB 

ports on the back of the SkyView display.



Steve



On 5/20/2013 12:12 PM, robintaylor wrote:

 	  Quote: 	
		   



 Hi Bob,

 I have disconnected the audio output from the Skyviews and the noise goes away.

 Thanks,

 Robin





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=401001#401001

sprocket(at)vx-aviation.c
Guest

Posted: Mon May 20, 2013 5:46 pm Post subject: Radio interference

I found a great reduction in SkyView noise by disconnecting pin 30 totally. 

Both my audio system and the SkyView power ground are connected to the same 

point.  Connecting pin 30 actually creates a ground loop in the system. 

It's easy to try it as long as your audio cables are grounded to the 

intercom end.  Connecting the case to ground may make the problem worse, 

depending on your wiring.



See details here: http://makerplane.org/forum/viewtopic.php?f=23&t=137



Thx,

Vern

--

robintaylor

Joined: 25 Apr 2013
Posts: 7

Posted: Wed May 22, 2013 2:17 am Post subject: Re: Radio interference

Thanks for the advice.

I haven't connected a ground to the Skyview case, I couldn't see it in my instructions.

My noise is not a hum, it is a distinct beep or pulse at a about two per second on tick over and increases in frequency with the rpm's.

I will disconnect the grounds from pin 30 and see if this has any effect.

I have spoken to Dynon and their view is that the problem is with the main ground to the engine either in size or quality. It is a 4g wire so it should be OK. I will check the terminals but I think they are OK.

Every ground in the plane goes back to a forest on the fire wall with the engine ground connected to the securing bolt for this.

Someone has suggested putting a condenser on the alternator output. Would this help.

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