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RF noise from EFIS

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N777TY

Joined: 09 Apr 2006
Posts: 69
Location: Charlotte, NC

Posted: Mon Mar 12, 2007 2:33 pm Post subject: RF noise from EFIS

Trying to figure out a problem I'm running into where an EFIS screen seems to be putting RF noise into my radio.



The noise seems "small" -- as in it can't be heard if there's a strong signal being received, but can be heard if there's no transmission or as background while receiving poor signal.  It never breaks the squelch on the radio at all, so it can only be heard if I pull the squelch button on my SL-40.



noise goes away if antenna is disconnected, in which case all I can hear is normal radio static.



noise can be heard if rubber ducky antenna is connected instead of the Comant antenna (so I'm not sure it's my real antenna installation at issue here, but could be?)  Due to the setup I have, I can hook this antenna right behind the radio, or at the end of the coax run.. didn't notice any difference between the two.



Tried Radio Shack ferrite choke at various locations and it didn't seem to do anything.



Tried some RS in-line choke (in-line with radio +, as well as EFIS + and ground) which also didn't do anything either.

coax doesn't run close to the EFIS screen, and for the most part, it's not close to other wires.



I have a 2-screen setup and both (and either) produce this noise...

have not tried transmitting, so no idea what kind of impact it'd have (if any) on outgoing transmissions.. focused on reception at this point.



again, since it doesn't break the squelch, it's not a big big issue, but it's annoying and would love to see it go away 

any thoughts?

Thanks!

Radomir

_________________
RV-7A
N777TY

pbraswell(at)alterthought
Guest

Posted: Mon Mar 12, 2007 6:18 pm Post subject: RF noise from EFIS

Bet you've got an BMA E1?



I had the same problem.  Got into the system setup and go to RF squelch.  The factory setting is 56.  I had to run my up to 70 to get rid of the scratching in my system.  All is well now...



Those ferrite thingies from RS DO NOT WORK!



peter



---

mlas(at)cox.net
Guest

Posted: Tue Mar 13, 2007 6:22 am Post subject: RF noise from EFIS

Radio,



What kind of EFIS?  Not all EFIS systems are created equal!  I would bet

that you have a BMA system!  If so, I have worked with a few customers

with similar problems.  The only thing that helped was to incorporate

shielded wires (which BMA doesn't like to use) and move the antenna away

from the main processor.  The BMA stuff makes an unacceptable amount of

RF noise.  One of the many reasons they will never get a TSO.



Mike



--

n395v

Joined: 10 Jan 2006
Posts: 450

Posted: Tue Mar 13, 2007 6:56 am Post subject: Re: RF noise from EFIS

It affects the BMA Sport and Lites as well and is worse in composites than metal planes.



Actually BMA encourages the use of shielded wires for anything running out of the EFIS.



As mentioned above you should avoid if possible running any EFIS wiring near your antenna lines.



Also the can around the EFIS is not necessarily connected to the ground of the circuit boards so  the can itself should be grounded as well as the EFIS.



Look for any wires from the EFIS that terminate in a dead end ( are not connected to anything) and eliminate them they are acting as a transmit antenna. Likely culprits are ap disconnect wires on the stick running next to your PTT and engine monitoring circuits not yet hooked up.



The shield on sheilded cable should be grounded at both ends.

If you are not using a serial port turn it off.



Hopefully you can reduce the noise to a level where it can be overcome with the squelch setting as noted above.

_________________
Milt

N777TY

Joined: 09 Apr 2006
Posts: 69
Location: Charlotte, NC

Posted: Tue Mar 13, 2007 8:01 am Post subject: Re: RF noise from EFIS

Thanks guys.. just to clarify a few points:



  1)  It's not BMA... it's GRT.



  2)  It doesn't need squelch adjustment -- it never breaks the squelch.. doesn't even come close to that.



  3)  It doesn't affect normal transmissions -- those are recieved 5 by 5.. radio does a great job of getting rid of all that noise when good transmission is received.



  4)  coax doesn't run close to any efis wires.. 

I ended up reviewing BMA message boards, and what I can see there is that BMA guys are A LOT more affected than I am... I don't have symptoms they're describing where increasing squelch takes care of the noise...

Thanks again!

Radomir

_________________
RV-7A
N777TY

nuckollsr(at)cox.net
Guest

Posted: Tue Mar 13, 2007 2:59 pm Post subject: RF noise from EFIS

At 07:56 AM 3/13/2007 -0700, you wrote:



 	  Quote: 	
		  



It affects the BMA Sport and Lites as well and is worse in composites than 

metal planes.



Actually BMA encourages the use of shielded wires for anything running out 

of the EFIS.


	


   Which suggests a profound lack of knowledge as

   to how noises should be kept inside the product . . .

 	  Quote: 	
		  As mentioned above you should avoid if possible running any EFIS wiring 

near your antenna lines.


	


   Antenna lines are coaxial transmission lines and not

   vulnerable to ingress of noises . . .

 	  Quote: 	
		  Also the can around the EFIS is not necessarily connected to the ground of 

the circuit boards so  the can itself should be grounded as well as the EFIS.


	


    "ground" is an un-quantified, un-qualified term term

    when it comes to taming the noises emitted from an

    accessory. Spent the whole day in the lab today "sniffing"

    the noise performance of an airborne super-server that's

    destined to share volume within an airplane with lots of

    VERY sensitive spook receivers.



    Anyone who pushes their noise containment duties off on

    the installer by suggesting broad brush admonitions to

    shield everything and keep stuff away from coaxes doesn't

    have a clue . . .

 	  Quote: 	
		  Look for any wires from the EFIS that terminate in a dead end ( are not 

connected to anything) and eliminate them they are acting as a transmit 

antenna. Likely culprits are ap disconnect wires on the stick running next 

to your PTT and engine monitoring circuits not yet hooked up.



The shield on sheilded cable should be grounded at both ends.

If you are not using a serial port turn it off.


	




    Let's do some detective work and see if the real

    leak can be identified before you start shot-gunning

    with hopeful remedies.



    What radio is being affected? Know that most of the

    glass dial noise problems radiate from the opening

    covered by the LCD. What does the "noise" sound like?

    How is the noise affected by positioning various controls

    of the victim radio?



        Bob . . .



        ----------------------------------------

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

N777TY

Joined: 09 Apr 2006
Posts: 69
Location: Charlotte, NC

Posted: Tue Mar 13, 2007 4:07 pm Post subject: Re: RF noise from EFIS

Bob,



It may be hard to describe the noise, so I figured a video may help   Here's a 1-minute video of my sniffing around with a handheld scanner (squelch turned down completely):



  http://www.vitez.net/noise.wmv



You'll notice a few spots where there's no noise and you just hear regular radio static..   Maybe ignore that weird noise when scanner is under the panel, as I don't hear it like that in my panel radio.

The radio is Garmin SL-40.  Not sure what you mean by positioning of controls.. 



Also, the radio (well, both SL-40 and handheld) does a great job of "killing" the noise when it receives even a semi-decent transmission.. so this noise doesn't actually affect reception, except for very, very weak ones (where the noise can just about barely be heard in the background).  However, it sounds horrible (and loud) when there's no transmission and squelch is pulled.  Again, it never breaks the squelch...  So, push the squelch and you'll probably never hear it (or barely ever notice it's there).. but I'm looking for "perfection" here 



The radio has this mode where it shows the signal level, and for RF level it shows around 18 when screens are off.. then jumps to about 40 when screens are turned on.... Not sure what these numbers exactly mean or what units those are.. but there's definitely a difference.  (this is with no transmissions being received).

Not sure if I mentioned this -- all these units are grounded on the firewall at a common grounding block.  Tried grounding locally on the panel (both radio and screens as well as screens alone) and that didn't make any difference.



One thing I haven't tried yet is transmitting -- not sure if there's any affect on clarity or strength of outgoing transmissions.. 

Any ideas are appreciated.  Or am I getting worked up about nothing?



Thanks!

Radomir

_________________
RV-7A
N777TY

n395v

Joined: 10 Jan 2006
Posts: 450

Posted: Tue Mar 13, 2007 6:06 pm Post subject: Re: RF noise from EFIS

 	  Quote: 	
		     Which suggests a profound lack of knowledge as

   to how noises should be kept inside the product 	




You just can't resist a dig at Greg can you?



Now I know why so many others think you are an asshole.



Do not archive.

_________________
Milt

rdunhamtn(at)hotmail.com
Guest

Posted: Wed Mar 14, 2007 4:28 am Post subject: RF noise from EFIS

Milt,



I see no mention by Bob of any particular personality! Your comments reflect 

your own personal prejudice and have nothing to do with the comments of our 

mentor and friend.



Let the "so many others" speak for themselves. Nobody elected you 

spokesperson. If you have such a negative opinion of our moderator why not 

just go away and play somewhere else where you DO like the moderator?



Grow up. Get a life. Get some discipline. That hot temper may get you killed 

in that Rocket some day!

Rodney in Tennessee



DO NOT ARCHIVE





 	  Quote: 	
		  From: "N395V" <n395v(at)hughes.net>

Reply-To: aeroelectric-list(at)matronics.com

To: aeroelectric-list(at)matronics.com

Subject: Re: RF noise from EFIS

Date: Tue, 13 Mar 2007 19:06:25 -0700




 >    Which suggests a profound lack of knowledge as

 >    to how noises should be kept inside the product

You just can't resist a dig at Greg can you?



Now I know why so many others think you are an asshole.



Do not archive.



--------

Milt

N395V

F1 Rocket

www.excaliburaviation.com





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=100393#100393






	


_________________________________________________________________

With tax season right around the corner, make sure to follow these few 

simple tips. 

http://articles.moneycentral.msn.com/Taxes/PreparationTips/PreparationTips.aspx?icid=HMFebtagline

n395v

Joined: 10 Jan 2006
Posts: 450

Posted: Wed Mar 14, 2007 5:07 am Post subject: Re: RF noise from EFIS

Rodney,



You are correct, Bob did not name any particular personality in his comment..



 	  Quote: 	
		  Which suggests a profound lack of knowledge 	




However, in context it can be presumed to be aimed at either me or Blue Mountain (aka Greg). Given history I presumed it was aimed at Greg.



In either case the words "suggests a profound lack of knowledge" are an eloquent way of saying you are stupid.



This I take as an insult.  There are many ways in which Bob could have structured his response to make his point, such as, "my experience suggests that a better way to approach this problem would be to....." but he chose terms that I find insulting no matter who they are aimed at.



You and others may find my language offensive but if you are going to insult someone I see no need to hidei t with eloquence.



As far as my going away Bob can take care of that ith the push of a button. Short of that you will have to suffer my occassional presence as there are many others on this list whose valuable contributions I find useful.

_________________
Milt

cjensen(at)dts9000.com
Guest

Posted: Wed Mar 14, 2007 5:38 am Post subject: RF noise from EFIS

Eloquence coutns.  Even when slapped in the face, I much prefer it with

a velvet glove!!



Chuck Jensen

--

nuckollsr(at)cox.net
Guest

Posted: Wed Mar 14, 2007 6:07 am Post subject: RF noise from EFIS

At 07:06 PM 3/13/2007 -0700, you wrote:



 	  Quote: 	
		  

 >    Which suggests a profound lack of knowledge as

 >    to how noises should be kept inside the product

You just can't resist a dig at Greg can you?


	


   I can't resist a dig at poor science and equally

   poor teaching. Read my most earnest attempts to

   engage Greg in lucid, useful dialog at:



http://aeroelectric.com/articles/richter/richter.html



   This exchange took place AFTER he took a whack at

   the AeroElectric Connection when he said, "I've

   seen so much truly atrocious work, much of it per

   Bob's book". But when asked to point out any

   writing in the 'Connection so poorly written as

   to induce one to do atrocious work, he was silent.

 	  Quote: 	
		  Now I know why so many others think you are an asshole.


	


   This isn't about me and Greg, it's about doing the

   best we know how to do for a price that a customer

   is happy to have paid. Products offered from the

   BMA website fall demonstrably short of those goals.



   I kept my assessments to myself for years but Greg

   chose to open the door with no prompting from me.

   He then demonstrated a lack of ability and/or

   willingness to engage in good critical review.



   I can't help what people think when they're offering

   opinions based upon a lack of knowledge and understanding.

   I'll invite you to hang around the list for awhile

   and gather enough data about me and what the List is

   about toward the goal of formulating your own, informed

   opinion.



        Bob . . .



        ----------------------------------------

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

nuckollsr(at)cox.net
Guest

Posted: Wed Mar 14, 2007 7:03 am Post subject: RF noise from EFIS

Went back a few postings and found this . . .



 	  Quote: 	
		  Trying to figure out a problem I'm running into where an EFIS screen seems 

to be putting RF noise into my radio.


	


 	  Quote: 	
		  The noise seems "small" -- as in it can't be heard if there's a strong 

signal being received, but can be heard if there's no transmission or as 

background while receiving poor signal.  It never breaks the squelch on 

the radio at all, so it can only be heard if I pull the squelch button on 

my SL-40.


	


    When you say "small" . . . do you think it likely that you'll

    notice it in flight with wind and engine noises? I know this

    is a VERY subjective assessment. But I've worked with dozens of

    builders and airplane owners who struggled with noises heard

    in the quiet of the shop that would have been unnoticed in the air.



    I'm not suggesting that you shouldn't endeavor to know how

    the noise is happening and perhaps develop an approach to making

    it go away . . . but noise management is a give/take proposition

    and you MIGHT be spending a lot of $time$ on something that doesn't

    need fixing.



 	  Quote: 	
		  noise goes away if antenna is disconnected, in which case all I can hear 

is normal radio static.


	


    Good data . . . it's radiated noise coming in through the antenna.



 	  Quote: 	
		  noise can be heard if rubber ducky antenna is connected instead of the 

Comant antenna (so I'm not sure it's my real antenna installation at issue 

here, but could be?)  Due to the setup I have, I can hook this antenna 

right behind the radio, or at the end of the coax run.. didn't notice any 

difference between the two.


	


    Do you have a hand-held? Hand held radios with a rubber-duck

    or even short "probe" antennas of a couple inches long are helpful

    "sniffers". In the lab, I have access to a spectrum analyzer. It's

    a receiver that plots an amplitude vs. frequency display on a 'scope

    screen. I can attach a small probe to the end of a coax and poke

    around the noisy electro-whizzy to find where the noise is coming

    out.

 	  Quote: 	
		  Tried Radio Shack ferrite choke at various locations and it didn't seem to 

do anything.


	


    The snap-on ferrites are never useful for conducted noise

    and only effective starting at about 100 MHz and going up.

    I've never seed a problem at comm frequencies fixed with

    a snap-on ferrite. I have seen useful applications of ferrites

    at UHF frequencies . . . but in every case, these situations

    would have been better addressed INSIDE the electro-whizzy

    as part of the original design.



 	  Quote: 	
		  Tried some RS in-line choke (in-line with radio +, as well as EFIS + and 

ground) which also didn't do anything either.

coax doesn't run close to the EFIS screen, and for the most part, it's not 

close to other wires.

I have a 2-screen setup and both (and either) produce this noise...


	


    Okay, you need to "sniff". Take a coax from the back of

    your comm radio (or a handheld) and terminate the loose

    end with one of these:



http://www.aeroelectric.com/Pictures/Tools/Sniffer_Probes.jpg



    Poke around the openings and cables of the offending

    device to see if you can deduce the exit point for the

    noise. If you can't hear the noise with the suggested

    probes try larger ones.

 	  Quote: 	
		  Re AeroElectric-List RF noise.ems

have not tried transmitting, so no idea what kind of impact it'd have (if 

any) on outgoing transmissions.. focused on reception at this point.


	


    It's exceedingly remote that radiated noises get into

    transmitted signals.

 	  Quote: 	
		  again, since it doesn't break the squelch, it's not a big big issue, but 

it's annoying and would love to see it go away 


	


    Sure . . . let's do the sniffing and see if you can identify

    the egress point. But let's not ignore the possibility that

    this noise may not be worth running to ground.



    Bob . . .

nuckollsr(at)cox.net
Guest

Posted: Wed Mar 14, 2007 7:03 am Post subject: RF noise from EFIS

 	  Quote: 	
		  

This I take as an insult.  There are many ways in which Bob could have

structured his response to make his point, such as, "my experience

suggests that a better way to approach this problem would be to....."

but he chose terms that I find insulting no matter who they are aimed

at.


	


    Being insulted is a choice. When assessing words about me,

    they can be sorted into two pots: (1) the words illustrate

    facts which call for considered integration into my future

    actions or (2) they're meaningless. In neither case are they

    worthy of an emotional investment. I can be insulted only if

    I allow it.



    In the instance before us, there were no words about you

    only about poor science, lack of understanding and poor

    teaching based on those shortcomings. We all suffer from

    lack of understanding to some degree on every topic. It's

    incumbent upon good teachers to remedy the former before

    attempting to do the later.

    Bob . . .

nuckollsr(at)cox.net
Guest

Posted: Wed Mar 14, 2007 7:17 am Post subject: RF noise from EFIS

At 09:33 AM 3/14/2007 -0400, you wrote:

 	  Quote: 	
		  Rodney,



You are correct, Bob did not name any particular personality in his

comment..

 > Which suggests a profound lack of knowledge

However, in context it can be presumed to be aimed at either me or Blue

Mountain (aka Greg). Given history I presumed it was aimed at Greg.



In either case the words "suggests a profound lack of knowledge" are an

eloquent way of saying you are stupid.


	


    No, ignorant. Ignorance can be remedied by the civilized

    discourse between capable teachers and willing students.

    In this instance, Greg has yet to demonstrate a membership

    in either group.



 	  Quote: 	
		  As far as my going away Bob can take care of that with the push of a

button. Short of that you will have to suffer my occassional presence as

there are many others on this list whose valuable contributions I find

useful.


	


    I'm sorry that you don't find value in my offerings.

    This IS disheartening for a teacher to hear. If you

    perceive shortcomings in either the science or practice

    I have to offer, I'd be pleased to address those concerns.



    Nobody wants you to go away. Everybody wants our $time$

    spent here on the List to yield a good return on the

    investment.



        Bob . . .



        ----------------------------------------

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

mlas(at)cox.net
Guest

Posted: Wed Mar 14, 2007 7:25 am Post subject: RF noise from EFIS

I totally agree with Bob.  My experience with BMA and the folks there

have been the worst for me as compared to ALL of the other companies I

deal with (to many to list).  Let's summarize, BMA produces products

that at face value looks cool and if it worked as advertised would be a

good product.  But when you dig into the finer points of BMA products

such as: stability, installation, customer service, ergonomics, builder

philosophy, function, and price they all fall short as compared to

almost ALL the others.



I work in the field with builders of experimental homebuilt airplanes.

I spent seven years in an avionics shop, three years on a military R&D

project, and 30 years total aircraft maintenance.  I am not very

polished in my delivery of words when it comes to basic avionics.  I

express my experience and you take it for what its worth.



Here in Arizona we have a large group of builders who are actively

building.  We do not have any real profession support for avionics

available here, so we get by with the local knowledge and experience of

all the engineers and techs. here and of course Lectric Bob.  So far

we've had many successes and few failures.



Of the 35+ airplanes under construction (not flying yet) that I have

worked on in the past 365 days (this past year).  I have seen my share

of BMA products (including my own).  After dealing with BMA too many

times with problems I don't even call them any more.  I can say that I

have over 12 saves this past year regarding folks purchasing BMA stuff.

Those of you who have purchased BMA and managed to get it to work to an

acceptable level that's great.  I would just like to say there are a

whole host of products out there that perform much better.



Mike Larkin



--

mwcreek(at)frontiernet.ne
Guest

Posted: Wed Mar 14, 2007 3:46 pm Post subject: RF noise from EFIS

Mike,  



Thanks, that is good info.  Would you be willing to comment on Advanced

Flight Systems, Dynon, and Grand Rapids?  I'll be making panel decisions in

May so your experience could help me out a lot and I suspect I'm not alone.

I'll be mostly day and night VFR but want the option to do light IFR in the

future.



Thanks,

Mike Creek



--

RURUNY(at)aol.com
Guest

Posted: Wed Mar 14, 2007 6:23 pm Post subject: RF noise from EFIS

I've got a similar problem on my Zenith 701. 

 I wired the loudspeaker to the ICOM A200 as per its drawings mounted on the  front

 of the passenger seat. With my Dynon D10A on full bright I hear no buzzing  noise...but when I dim

 the Dynon using its built in dimming feature in the menu system, the buzz  gets louder and at a different 

 frequency. The more I dim the worse it is. I'm using single point  ground.

 No buzzing in headsets though,  maybe the noise is going directly into  the A200 to speaker and not into the

 403MC intercom to headsets. Whatever is used to dim your EFIS might be  making the noise. Something to play with...

  

 Brian Unruh

 Long Island, NY

 www.701Builder.com

  



AOL now offers free email to everyone.  Find out more about what's free from AOL at AOL.com. 

  [quote][b]

mlas(at)cox.net
Guest

Posted: Wed Mar 14, 2007 7:17 pm Post subject: RF noise from EFIS

Mike,



I have worked with all of the companies you have listed.  I will try and

keep this brief.  A quick note, I find that the best way to figure out

what you need it to start with the systems that have the functions you

want and then start sorting out the weaker ones.  Do a pro / con list.



Advanced Flight Systems, they make very good products.  I have only

worked with their AF-2002/AF-2500 engine monitor.  It's a great product,

very stable, and most importantly the people are great to work with.

For example, one system we were installing had a power problem and the

AFS folks worked with us until we figured it out.  They were ready to

send a new unit if that's what it took.  Every time I speak with them

it's a great experience.  I have seen their EFIS unit and chatted with

them about it but have not installed or flown behind one yet.  If it is

like their other products it should be great.



Dynon, I was one of their first customers back in the D-10 days.  The

company was small and the product very new.  I had some minor problems

and they were very quick to fix address them.  Since that time I have

worked on some installations with the newer units and find the product

much improved from version one.  The people there are easy to work with

and know their product well.  I have only experienced one failure and

that was a new unit that would not boot properly and Dynon repaired it

in record time.



Grand Rapids Technology, I have two GRT EIS systems myself and have

installed many of their ADC units on the crossbow Chelton EFIS systems.

Their stuff isn't the most glamorous, but it works very well and I have

not seen one fail yet.  I have chatted with them many time at various

shows and for tech support and they are always very knowledgeable and

helpful.  As far as the EFIS system goes, I have only flown behind one.

I have not personal installed one.



If you have more questions, email me at mlas(at)cox.net.  I will be away

until March 18th.



Mike Larkin

--

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