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NAV splitter grounded?

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rv10rob(at)gmail.com
Guest

Posted: Fri Jun 01, 2012 5:34 pm Post subject: NAV splitter grounded?

Quick question: Should the Comant CI-507 Nav/GS splitter (between my antenna and GNS430) be isolated from the airframe ground?  Seems like the answer is "yes" but I didn't think about it when wiring my panel, and it's currently not isolated.  I'm thinking this could be responsible for my "jumpy" needles.

  

-Rob

-- 



Rob Kochman

RV-10 Flying since March 2011

 Woodinville, WA

 http://kochman.net/N819K



  [quote][b]

dave.saylor.aircrafters(a
Guest

Posted: Fri Jun 01, 2012 6:09 pm Post subject: NAV splitter grounded?

Rob,



The case is almost certainly grounded through the coax shield (check

continuity from the connector barrel to the case).  If the case is

metal I'd think it wouldn't matter if were mechanically grounded or

not.



Dave Saylor

831-750-0284 CL

On Fri, Jun 1, 2012 at 6:33 PM, Rob Kochman <rv10rob(at)gmail.com> wrote:

 	  Quote: 	
		   Quick question: Should the Comant CI-507 Nav/GS splitter (between my antenna

 and GNS430) be isolated from the airframe ground?Â  Seems like the answer is

 "yes" but I didn't think about it when wiring my panel, and it's currently

 not isolated.Â  I'm thinking this could be responsible for my "jumpy"

 needles.



 -Rob



 --

 Rob Kochman

 RV-10 Flying since March 2011

 Woodinville, WA

 http://kochman.net/N819K

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Jun 02, 2012 5:52 am Post subject: NAV splitter grounded?

At 08:33 PM 6/1/2012, you wrote:

 	  Quote: 	
		  Quick question: Should the Comant CI-507 Nav/GS splitter (between my 

antenna and GNS430) be isolated from the airframe ground?  Seems 

like the answer is "yes" but I didn't think about it when wiring my 

panel, and it's currently not isolated.  I'm thinking this could be 

responsible for my "jumpy" needles.


	


    As Dave pointed out, the metallic enclosure

    of your splitter has continuity to ground

    by way of the coax shields that are tied

    to it through the connectors.



    Things that go on 'inside the wall of shields'

    in a feed line system is pretty much an isolated

    world. Just how and where the shields get tie

    to the airframe . . . or whether they ever get

    tied to airframe has no influence upon the

    business of getting radio frequency power from

    one end to the other.



    Are you seeing similar symptoms with more than

    one steering needle? Both VOR or is one of them

    a Glide Slope?

   Bob . . .

rv10rob(at)gmail.com
Guest

Posted: Sun Jun 03, 2012 8:41 am Post subject: NAV splitter grounded?

Thanks, guys... I have only one nav radio, and I'm seeing jumpy needles on both the lateral (VOR and localizers) as well as glideslope.  GPS needle (lateral only) is rock solid.  I have this antenna: http://www.rami.com/product-view.php?pid=8.  It's mounted under the horizontal stabilizer on an RV-10.  Going to do more testing today.

   

 -Rob



 On Sat, Jun 2, 2012 at 6:50 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>  



At 08:33 PM 6/1/2012, you wrote:

  	  Quote: 	
		  Quick question: Should the Comant CI-507 Nav/GS splitter (between my antenna and GNS430) be isolated from the airframe ground?  Seems like the answer is "yes" but I didn't think about it when wiring my panel, and it's currently not isolated.  I'm thinking this could be responsible for my "jumpy" needles.

 	




  As Dave pointed out, the metallic enclosure

  of your splitter has continuity to ground

  by way of the coax shields that are tied

  to it through the connectors.



  Things that go on 'inside the wall of shields'

   in a feed line system is pretty much an isolated

  world. Just how and where the shields get tie

  to the airframe . . . or whether they ever get

  tied to airframe has no influence upon the

  business of getting radio frequency power from

   one end to the other.



  Are you seeing similar symptoms with more than

  one steering needle? Both VOR or is one of them

  a Glide Slope?

 Bob . . . 

  ===========================================

_ities such as List Un/Subscription,

 www.matronics.com/Navigator?AeroElectric-List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

 ======================ttp://forums.matronics.com/" target="_blank">http://forums.matronics.com

 ======================       -Matt Dralle, List Admin.

 ================================



 



	


-- 

 Rob Kochman

RV-10 Flying since March 2011

 Woodinville, WA

 http://kochman.net/N819K



  [quote][b]

skywagon

Joined: 11 Feb 2006
Posts: 184

Posted: Sun Jun 03, 2012 9:28 am Post subject: NAV splitter grounded?

I am wondering if the antenna, mounted under the all metal  airframe is possibly seeing multiple images off the metal structures with  phasing caused by the different paths.....

 D

  

   

 [quote]   ---

john.maccallum(at)bigpond
Guest

Posted: Mon Jun 04, 2012 12:48 am Post subject: NAV splitter grounded?

It will depend on the type  of Antenna and where it is mounted but ordinarily it would not matter if the spacing between the Antenna and another object]is more than a qtr wave.

Mulitpath and  Rayleighan fading will vary constant anyway on a moving object such as an aircraft. 

 

 

Cheers

John MacCallum

Builder #41016

VH-DUU

 

 

 

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of David Lloyd

Sent: Monday, 4 June 2012 3:27 AM

To: aeroelectric-list(at)matronics.com

Subject: Re: NAV splitter grounded?

 

I am wondering if the antenna, mounted under the all metal airframe is possibly seeing multiple images off the metal structures with phasing caused by the different paths.....



D



 

[quote]

---

Martymason

Joined: 17 Apr 2009
Posts: 20
Location: Norcross, GA

Posted: Mon Jun 04, 2012 10:05 am Post subject: Re: NAV splitter grounded?

Rob,

If you only have one NAV receiver connected to the splitter, then the second leg of the splitter is open and is not terminated. This condition will result in reflected signals at the connected receiver and may result in your jumpy needles. I would remove the un-needed splitter and connect the antenna directly to the receiver using a BNC-BNC connector. If the jumpiness disapears then problem solved.

Marty Mason

Retired CATV engineer (Much work with antennas and co-axial cable networks)

_________________
Marty Mason
Norcross, GA

dlj04(at)josephson.com
Guest

Posted: Tue Jun 05, 2012 12:00 am Post subject: NAV splitter grounded?

Rob Kochman<mailto:rv10rob(at)gmail.com>   wrote



 	  Quote: 	
		    Thanks, guys... I have only one nav radio, and I'm seeing jumpy needles on

  both the lateral (VOR and localizers) as well as glideslope.  GPS needle

  (lateral only) is rock solid.  I have this antenna:

  http://www.rami.com/product-view.php?pid=8.  It's mounted under the

  horizontal stabilizer on an RV-10.  Going to do more testing today.


	


Can you provide a little more info on "jumpy needles?" Are you getting this in a place where the signals from the VOR or localizer and the glideslope are expected to be strong? If you fly the whole ILS, at some point (certainly before you reach the outer marker) both of these signals should be big enough to swamp any sort of interference in the airplane. Do you hear any unusual noises in the VOR/LOC audio? Someone suggested getting rid of the splitter but of course you need that to feed the glideslope receiver. As Bob suggested, there's not likely to be a grounding or ground loop issue no matter where the coax is grounded, but there can be lots of other problems.



--

David Josephson

rv10rob(at)gmail.com
Guest

Posted: Tue Jun 05, 2012 5:52 am Post subject: NAV splitter grounded?

Thanks, David... I need to do more testing before I can be sure of too much.  It seems to be better closer to the station, though it's sometimes still jumpy fairly close to the station.  It also seems to be worse in rain and clouds.  Here's a video that shows an example halfway down an ILS.  In this one, the localizer is stable, but the glideslope is moving around.

 http://www.youtube.com/watch?v=UkClTxpcPB8

 

I'll report back more info when I have it.  I do appreciate the help.

 

 -Rob

On Tue, Jun 5, 2012 at 12:58 AM, D L Josephson <dlj04(at)josephson.com (dlj04(at)josephson.com)> wrote:

 	  Quote: 	
		   --> AeroElectric-List message posted by: D L Josephson <dlj04(at)josephson.com (dlj04(at)josephson.com)>

 

 Rob Kochman<mailto:rv10rob(at)gmail.com (rv10rob(at)gmail.com)>   wrote

 

  	  Quote: 	
		    Thanks, guys... I have only one nav radio, and I'm seeing jumpy needles on

  both the lateral (VOR and localizers) as well as glideslope.  GPS needle

  (lateral only) is rock solid.  I have this antenna:

  http://www.rami.com/product-view.php?pid=8.  It's mounted under the

  horizontal stabilizer on an RV-10.  Going to do more testing today.

 	
 

 Can you provide a little more info on "jumpy needles?" Are you getting this in a place where the signals from the VOR or localizer and the glideslope are expected to be strong? If you fly the whole ILS, at some point (certainly before you reach the outer marker) both of these signals should be big enough to swamp any sort of interference in the airplane. Do you hear any unusual noises in the VOR/LOC audio? Someone suggested getting rid of the splitter but of course you need that to feed the glideslope receiver. As Bob suggested, there's not likely to be a grounding or ground loop issue no matter where the coax is grounded, but there can be lots of other problems.

  

 --

 David Josephson

 

  

 

 ====================================

 -List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

 ====================================

 http://forums.matronics.com

 ====================================

 le, List Admin.

 ="_blank">http://www.matronics.com/contribution

 ====================================

 

 

 

 	


-- 

Rob Kochman

RV-10 Flying since March 2011

 Woodinville, WA

 http://kochman.net/N819K



  [quote][b]

dlj04(at)josephson.com
Guest

Posted: Wed Jun 06, 2012 8:53 am Post subject: NAV splitter grounded?

On 6/5/12 11:56 PM, AeroElectric-List Digest Server wrote:

 	  Quote: 	
		   Time: 06:52:58 AM PST US

 Subject: Re: Re: NAV splitter grounded?

 From: Rob Kochman<rv10rob(at)gmail.com>

 Thanks, David... I need to do more testing before I can be sure of too

 much.  It seems to be better closer to the station, though it's sometimes

 still jumpy fairly close to the station.  It also seems to be worse in rain

 and clouds.  Here's a video that shows an example halfway down an ILS.  In

 this one, the localizer is stable, but the glideslope is moving around.

 http://www.youtube.com/watch?v=UkClTxpcPB8

It almost looks to me as though the integration time on the Dynon is too 

fast. Is there a way to slow it down so the variations are damped a 

little better?

It's helpful to be able to listen to the LOC and GS signals in real time.

What GS receiver are you using?  You may be able to hear whether the 

signal is just weak (high level of hiss relative to the 90 and 150 Hz 

LOC/GS modulation) or if there are some periodic noises that you can 

correlate with strobes, wig-wag, alternator whine, ignition noise, etc.

--

David Josephson

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