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Intercom feedback at low rpm

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Rebel56

Joined: 10 Dec 2014
Posts: 11

Posted: Sun Jan 14, 2018 5:22 pm Post subject: Intercom feedback at low rpm

Recently I have started hearing static feedback from the intercom during taxi and low rpm such as landing. the noise goes away during flight when rpms are up.. Have been flying for over 100 hours with no trouble, until now.  Flightcom  2 person intercom, viking honda engine on a Murphy Rebel.

fherr(at)cfl.rr.com
Guest

Posted: Sun Jan 14, 2018 6:26 pm Post subject: Intercom feedback at low rpm

How is your battery - holding a charge and in good condition otherwise?

On Jan 14, 2018, at 8:22 PM, Rebel56 <Rebel56(at)rogers.com> wrote:






Recently I have started hearing static feedback from the intercom during taxi and low rpm such as landing. the noise goes away during flight when rpms are up.. Have been flying for over 100 hours with no trouble, until now.  Flightcom  2 person intercom, viking honda engine on a Murphy Rebel.





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=477287#477287

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Sun Jan 14, 2018 6:28 pm Post subject: Intercom feedback at low rpm

Do you have a cigar lighter to USB adapter anywhere in the cockpit? For 

an Ipad or Iphone, etc?



On 1/14/2018 6:22 PM, Rebel56 wrote:

 	  Quote: 	
		   

 

 Recently I have started hearing static feedback from the intercom during taxi and low rpm such as landing. the noise goes away during flight when rpms are up.. Have been flying for over 100 hours with no trouble, until now.  Flightcom  2 person intercom, viking honda engine on a Murphy Rebel.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=477288#477288

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

ceengland7(at)gmail.com
Guest

Posted: Sun Jan 14, 2018 6:32 pm Post subject: Intercom feedback at low rpm

On 1/14/2018 7:22 PM, Rebel56 wrote:

 	  Quote: 	
		   



 Recently I have started hearing static feedback from the intercom during taxi and low rpm such as landing. the noise goes away during flight when rpms are up.. Have been flying for over 100 hours with no trouble, until now.  Flightcom  2 person intercom, viking honda engine on a Murphy Rebel.

Need to be more specific describing the symptoms. Feedback (usually a 
	


squeal or howl) is very different from static, and static can be a lot 

of different sounds. Is it more of a whine, that changes pitch with rpm? 

(likely failing diodes in the alternator) Is it a crackling buzz? Does 

it really go away, or can you just not hear it over the increased noise 

in the cockpit at higher power settings?



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Rebel56

Joined: 10 Dec 2014
Posts: 11

Posted: Sun Jan 14, 2018 6:34 pm Post subject: Re: Intercom feedback at low rpm

Battery is in good condition and holds charge.



I have two cigarette lighter adapters, one on each side of the panel.

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Sun Jan 14, 2018 6:38 pm Post subject: Intercom feedback at low rpm

Some USB or mini-USB adapters are bad offenders in the static generation 

business.



On 1/14/2018 7:34 PM, Rebel56 wrote:

 	  Quote: 	
		   

 

 Battery is in good condition and holds charge.

 

 I have two cigarette lighter adapters, one on each side of the panel.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=477295#477295

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

Rebel56

Joined: 10 Dec 2014
Posts: 11

Posted: Sun Jan 14, 2018 6:39 pm Post subject: Re: Intercom feedback at low rpm

Been a while since I flew, but I think it could be both, a slight whine, and static. I can quiet it with the squelch, but doing so also quiets all radio traffic. It really seems to disappear when the rpms increase.

Last edited by Rebel56 on Sun Jan 14, 2018 6:40 pm; edited 1 time in total

Rebel56

Joined: 10 Dec 2014
Posts: 11

Posted: Sun Jan 14, 2018 6:41 pm Post subject: Re: Intercom feedback at low rpm

Thanks kellym, I had thought of that as well, and tried unplugging the usb adapter - but no change.

ceengland7(at)gmail.com
Guest

Posted: Sun Jan 14, 2018 6:47 pm Post subject: Intercom feedback at low rpm

On 1/14/2018 8:39 PM, Rebel56 wrote:

 	  Quote: 	
		   



 Been a while since I flew, but I think it could be both, a slight whine, and static. I can quiet it with the squelch, but doing so also quiets all radio traffic.

Who were you answering? (Need to quote the person you're replying to, if 
	


there are multiple possibilities.)



If it was me, does it change frequency with engine rpm?



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Rebel56

Joined: 10 Dec 2014
Posts: 11

Posted: Sun Jan 14, 2018 6:53 pm Post subject: Re: Intercom feedback at low rpm

[quote="ceengland7(at)gmail.com"]On 1/14/2018 8:39 PM, Rebel56 wrote:

 	  Quote: 	
		   



 Been a while since I flew, but I think it could be both, a slight whine, and static. I can quiet it with the squelch, but doing so also quiets all radio traffic.

Who were you answering? (Need to quote the person you're replying to, if 

	


there are multiple possibilities.)



If it was me, does it change frequency with engine rpm?



---

It might change frequency ever so slightly, bu the static is constant and loud.

ceengland7(at)gmail.com
Guest

Posted: Mon Jan 15, 2018 6:26 am Post subject: Intercom feedback at low rpm

On Sun, Jan 14, 2018 at 8:53 PM, Rebel56 <Rebel56(at)rogers.com (Rebel56(at)rogers.com)> wrote:

 	  Quote: 	
		  --> Avionics-List message posted by: "Rebel56" <Rebel56(at)rogers.com (Rebel56(at)rogers.com)>

 [quote="ceengland7(at)gmail.com"]On 1/14/2018 8:39 PM, Rebel56 wrote:

 >

 >

 >  Been a while since I flew, but I think it could be both, a slight whine, and static. I can quiet it with the squelch, but doing so also quiets all radio traffic.

 > Who were you answering? (Need to quote the person you're replying to, if

 >

 there are multiple possibilities.)

 If it was me, does it change frequency with engine rpm?

 ---

 It might change frequency ever so slightly, bu the static is constant and loud.

If it doesn't change pitch or volume, it would seem to be unrelated to the engine itself. Have you shed all electrical loads, except the intercom itself? Try to eliminate every electrical device, to see if the noise stops after dropping one of them off line. Any device that contains a 'switcher' style power supply can generate a buzzing noise if it isn't properly filtered. USB power supplies, both LED & HID lighting, strobe lights, CD ignition systems, etc etc can all generate a crackling, buzzing kind of static.

And just to cover all bases, look at engine accessories, too. If possible on the Viking, shut down the alternator. (You should have some form of control over the alternator, to protect your avionics from an over-voltage event.) If it has redundant engine controllers, shut off one controller, then the other, like you would do when doing a mag check on a conventional a/c engine, to see if one of the controllers is causing the noise.

Something as simple as wiring architecture can also cause noise 'injection' into the system. If the plane isn't wired with the grounds from potential noise producers returning to a common point near the battery (meaning that they use a/c structure as the ground return), then noise produced by the device can be imposed on the power circuit of other, vulnerable devices, like the radio and intercom.

Hope that gives you some places to look.

Rebel56

Joined: 10 Dec 2014
Posts: 11

Posted: Mon Jan 15, 2018 3:52 pm Post subject: Re: Intercom feedback at low rpm

[quote="ceengland7(at)gmail.com"]On Sun, Jan 14, 2018 at 8:53 PM, Rebel56 <Rebel56> wrote:

 	  Quote: 	
		  --> Avionics-List message posted by: "Rebel56" <Rebel56>

  	  ceengland7(at)gmail.com wrote: 	
		  On 1/14/2018 8:39 PM, Rebel56 wrote:

 >

 >

 >  Been a while since I flew, but I think it could be both, a slight whine, and static. I can quiet it with the squelch, but doing so also quiets all radio traffic.

 > Who were you answering? (Need to quote the person you're replying to, if

 >

 there are multiple possibilities.)

 If it was me, does it change frequency with engine rpm?

 ---

 It might change frequency ever so slightly, bu the static is constant and loud.

If it doesn't change pitch or volume, it would seem to be unrelated to the engine itself. Have you shed all electrical loads, except the intercom itself? Try to eliminate every electrical device, to see if the noise stops after dropping one of them off line. Any device that contains a 'switcher' style power supply can generate a buzzing noise if it isn't properly filtered. USB power supplies, both LED & HID lighting, strobe lights, CD ignition systems, etc etc can all generate a crackling, buzzing kind of static.

And just to cover all bases, look at engine accessories, too. If possible on the Viking, shut down the alternator. (You should have some form of control over the alternator, to protect your avionics from an over-voltage event.) If it has redundant engine controllers, shut off one controller, then the other, like you would do when doing a mag check on a conventional a/c engine, to see if one of the controllers is causing the noise.

Something as simple as wiring architecture can also cause noise 'injection' into the system. If the plane isn't wired with the grounds from potential noise producers returning to a common point near the battery (meaning that they use a/c structure as the ground return), then noise produced by the device can be imposed on the power circuit of other, vulnerable devices, like the radio and intercom.

Hope that gives you some places to look. 	

Thanks, all good ideas. When it warms up I will have to start investigating again. Interesting that nothing on the AC has changed, but the noise just started. Loose wire maybe.

wjrhamilton(at)optusnet.c
Guest

Posted: Mon Jan 15, 2018 6:50 pm Post subject: Intercom feedback at low rpm

Folks,Not certain I have seen it mentioned, but are all the earths clean and with minimum resistance.

Last time I had an intractable nuisance like this, it finally turned out to be a badly earthed headset (female) plug.

Cheers,

Bill Hamilton

[quote]

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