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fvalarm(at)rapidnet.net
Guest

Posted: Mon Apr 11, 2016 10:39 pm Post subject: RF Interference

Here's a challenge for the brains.   

Suddenly my fuel pressure indication has become the victim of RF interference.  I've had the airplane off-line for some mods and upgrades and during this time has come down with a severe case of RF-itis.  

Symptoms:   

When I push the PTT, the fuel pressure indication steadily climbs as a rate of about 5 psi/second as long as it's maintained all the way to 60 PSI (engine and fuel pump off).  This occurs with either comm radio (each has it's own antenna, feed line and routing), although one radio only gets the error up to about 30-40 PSI.  A handheld has a similar effect but to a lesser degree presumably because it has less transmit power.  

Note;  ATC has no problem hearing my transmissions with either radio.   

Things that I have changed since taking the airplane off-line when everything had been working fine:   

A) Replaced one comm antenna (bent whip on fuselage bottom) with a new straight antenna installed on the rear turtle deck.  This required extending the coax with BNC and RG400 cable.  This is the radio/antenna combination that has the lesser effect on the fuel pressure reading.  The other radio/antenna system was not modified in any way. This radio has the larger effect on the fuel pressure reading.  

B) Added a VHF tracker radio which transmits a "bread-crumb" every 120 seconds.     

C) The engine monitor was sent to the factory for a software upgrade that wasn't needed after all and therefore nothing was done and re-installed.  

Equipment:   

A) The fuel pressure sender is GRT's HPS-SS-01 which has three wires and a 4th (shield) not to be connected.  Details here...  

http://www.grtavionics.com/documents/EIS/100%20psi%20SS%2012V%20Pressure%20Sensor.pdf   

I suspect this transducer has some electronics inside that are possibly affected by RF in turn sending an erroneous reading out to the engine monitor.  

B) Engine monitor is GRT's EIS 4000.   

What I have done so far...   

A) Installed ferrite cores (6 so far) around all the wires coming out of the sender, at the sender.  This has caused the RF interference to be dramatically reduced to a 4-6 PSI change (depending on which radio) while in the hangar, but in the air, the interference still steadily climbs with application of PTT.  The output voltage on the signal wire (disconnected from the engine monitor) sits idle at 1 volt but climbs steadily to over 4 volts with PTT/RF.  The ferrite cores hold the voltage rise to about 200 mV.  

B) I spoke to tech support at GRT today.  They said if anything, put the ferrite core around just the sender's signal wire where it goes into the engine monitor.  I installed one ferrite core there today (leaving all the others in place) and this had no noticeable effect in the hangar.  I think the RF is affecting the sender, not the monitor.  

C) The problem occurs whether the VHF tracker is turned on or not.  I even took the fuse out so this system has nothing connected to the power bus.  I have not removed the antenna however to see if it is somehow coupling the comm's RF into the airframe via the ground wire.  Is this possible?  The radio that has the largest effect has it's antenna closest to the tracker antenna on the fuse bottom.  The VHF tracker works as advertised.     

Questions:   

What is going on here?     

Is it likely to be a sender has suddenly gone bad?     

What about that shield wire that comes out of the sender that is not to be connected to anything?  What good is it if not connected to anything?  The wiring is not shielded between the sender and the engine monitor.  The sender's wiring was not modified in anyway during the aircraft's upgrades.  

Is the Tracker's antenna feeding RF back into the airframe?   

Any other ideas?

 

 Bevan

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Apr 12, 2016 7:33 am Post subject: RF Interference

B) Engine monitor is GRT's EIS 4000. 



 What I have done so far... 



 A) Installed ferrite cores (6 so far) around all the wires coming out of the sender, at the sender.  This has caused the RF interference to be dramatically reduced to a 4-6 PSI change (depending on which radio) while in the hangar, but in the air, the interference still steadily climbs with application of PTT.  The output voltage on the signal wire (disconnected from the engine monitor) sits idle at 1 volt but climbs steadily to over 4 volts with PTT/RF.  The ferrite cores hold the voltage rise to about 200 mV.



     EMI interference mitigation with the

     ferrite cores is a bit iffy . . . it's

     also dependent on what kind of ferrite.

     Ferrite for radio frequency inductors and

     transformers is optimized for minimum

     losses while ferrites for converting stray

     energies to heat are designed to exhibit

     losses.



     High quality ferrites can be components

     of a filter network of an inductor and one

     or more capacitors.



 B) I spoke to tech support at GRT today.  They said if anything, put the ferrite core around just the sender's signal wire where it goes into the engine monitor.  I installed one ferrite core there today (leaving all the others in place) and this had no noticeable effect in the hangar.  I think the RF is affecting the sender, not the monitor.

   

     Good supposition. 



 C) The problem occurs whether the VHF tracker is turned on or not.  I even took the fuse out so this system has nothing connected to the power bus.  I have not removed the antenna however to see if it is somehow coupling the comm's RF into the airframe via the ground wire.  Is this possible?  The radio that has the largest effect has it's antenna closest to the tracker antenna on the fuse bottom.  The VHF tracker works as advertised.   



 Questions: 



 What is going on here?  



 Is it likely to be a sender has suddenly gone bad?  

    

    Not likely . . .



 What about that shield wire that comes out of the sender that is not to be connected to anything?  What good is it if not connected to anything?  The wiring is not shielded between the sender and the engine monitor.  The sender's wiring was not modified in anyway during the aircraft's upgrades.



   

 Is the Tracker's antenna feeding RF back into the airframe? 

  

    Probably not. Can you tell me who makes

    the pressure transducer and what its part

    number is?



    I may have a 'fix' but I need more data before

    I can recommend it with any confidence.

 

   Bob . . .

fvalarm(at)rapidnet.net
Guest

Posted: Tue Apr 12, 2016 8:42 am Post subject: RF Interference

Hi Bob,

  

 I believe this is the sender...

  

 MSP 300-100-P-4-A-1   see...

  

 http://www.mouser.com/ds/2/418/MSP300-769580.pdf

  

 Thanks.  

  

 I'm going out to the hangar to remove the VHF Tracker  antenna and re-test to try and rule out that path back into the aircraft.   Will report back soon.

  

 Bevan



   From:  owner-aeroelectric-list-server(at)matronics.com  [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert  L. Nuckolls, III

Sent: Tuesday, April 12, 2016 8:32 AM

To:  aeroelectric-list(at)matronics.com

Subject: Re: RF  Interference

 

B) Engine monitor is GRT's EIS 4000. 



What I have  done so far... 



A) Installed ferrite cores (6 so far) around all the  wires coming out of the sender, at the sender.  This has caused the RF  interference to be dramatically reduced to a 4-6 PSI change (depending on which  radio) while in the hangar, but in the air, the interference still steadily  climbs with application of PTT.  The output voltage on the signal wire  (disconnected from the engine monitor) sits idle at 1 volt but climbs steadily  to over 4 volts with PTT/RF.  The ferrite cores hold the voltage rise to  about 200 mV.



    EMI interference mitigation with  the

    ferrite cores is a bit iffy . . .  it's

    also dependent on what kind of  ferrite.

    Ferrite for radio frequency inductors  and

    transformers is optimized for  minimum

    losses while ferrites for converting  stray

    energies to heat are designed to  exhibit

    losses.



    High quality  ferrites can be components

    of a filter network of an  inductor and one

    or more capacitors.



B) I spoke  to tech support at GRT today.  They said if anything, put the ferrite core  around just the sender's signal wire where it goes into the engine  monitor.  I installed one ferrite core there today (leaving all the others  in place) and this had no noticeable effect in the hangar.  I think the RF  is affecting the sender, not the monitor.

  

     Good supposition. 



C) The problem occurs whether the VHF tracker  is turned on or not.  I even took the fuse out so this system has nothing  connected to the power bus.  I have not removed the antenna however to see  if it is somehow coupling the comm's RF into the airframe via the ground  wire.  Is this possible?  The radio that has the largest effect has  it's antenna closest to the tracker antenna on the fuse bottom.  The VHF  tracker works as advertised.   



Questions: 



What is  going on here?  



Is it likely to be a sender has suddenly gone  bad?  

   

   Not likely . . .



What  about that shield wire that comes out of the sender that is not to be connected  to anything?  What good is it if not connected to anything?  The  wiring is not shielded between the sender and the engine monitor.  The  sender's wiring was not modified in anyway during the aircraft's  upgrades.



  

Is the Tracker's antenna feeding RF back into the  airframe? 

 

   Probably not. Can you tell me who  makes

   the pressure transducer and what its part

    number is?



   I may have a 'fix' but I need more data  before

   I can recommend it with any confidence.

 

  Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1925
Location: Riley TWP Michigan

Posted: Tue Apr 12, 2016 10:12 am Post subject: Re: RF Interference

It is common practice to connect a shield at one end only, however follow the manufacturer's recommendation.  Assuming that the sender's wires have been extended, here are some suggestions:

1. Twist the extension wires together.  An easy way to do that is to chuck the wire ends in a drill.

2. Use shielded extension wire with the shield grounded at one end only.  Do not connect the two shields together.

3. Loop the wire at the sender end with the loop going through a ferrite bead.

_________________
Joe Gores

fvalarm(at)rapidnet.net
Guest

Posted: Tue Apr 12, 2016 11:20 am Post subject: RF Interference

Ok,  Just got back from the hangar.



Just now I removed the VHF Tracker antenna, disconnected all new wires going

in/out of the tracker and hit the PTT.  No change.  I'm still getting a 5

PSI rise in fuel pressure (engine and boost pump off so pressure should

remain at zero).  I still have the ferrite cores installed at the fuel

pressure sender.  Without them, the pressure would climb to 60 PSI if I held

the PTT long enough.  I feel I can now rule out the tracker.



Just to recap, the high fuel pressure anomaly has not been a problem for the

first 40 hours of flying.  It has come on suddenly since I put the airplane

down for maintenance/upgrades (tracker install, new comm antenna/location

for comm 1, New OAT sender and location, plus a few other non-electrical

items).



I will focus on the OAT sender next.  It was a plastic jobber inside the

wing root.  I never should have put it there in the first place.  I just did

as suggested.  I have moved it to under the wing on the first inspection

panel.  It is now a SS version which protrudes through the skin.  It feeds a

signal back to the engine monitor (EIS4000).  It has a ground wire and a

signal wire.



Bevan



--

user9253

Joined: 28 Mar 2008
Posts: 1925
Location: Riley TWP Michigan

Posted: Tue Apr 12, 2016 12:02 pm Post subject: Re: RF Interference

Where is the fuel pressure sender grounded at? It should be grounded at the display unit, not locally.

_________________
Joe Gores

fvalarm(at)rapidnet.net
Guest

Posted: Tue Apr 12, 2016 12:20 pm Post subject: RF Interference

The sender is grounded where it always has been, at the forest of tabs,

single point ground point.



Thanks.



Bevan 



--

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Apr 12, 2016 1:34 pm Post subject: RF Interference

MSP transducers are generally pretty EMC robust. It's still

 a mystery as to what might have changed . . . but

 here's an experiment you can run to help divide

 and conquer.



 Take an AA alkaline cell and solder some 'pigtails'

 to the + and - terminals. Disconnect the tranducer

 at the engine end of the wiring and hook the

 aa battery + to white, - to black leads running

 back to the panel.



 Take ferrites off if convenient . . . 



 See what your EIS system reads . . . should

 be on the order of 50 pounds. The key a transmitter

 to observe effects.  If the readings are now steady,

 then the interference is upsetting the transducer.

 If the problem persists, then the real victim

 is the EIS panel box. 



 I can send you an itty-bitty filter that wires into the 

 transducer leads within short distance of the

 victim as identified by experiment . . .



 

 [img]cid:.0[/img]



 What are the wires between the EIS panel connector

 and the transducer? It would be good if they were a

 twisted trio with all panel end wires terminated

 at the EIS connector.



 

   Bob . . .

136d3db1.jpg

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fvalarm(at)rapidnet.net
Guest

Posted: Tue Apr 12, 2016 2:23 pm Post subject: RF Interference

Those are excellent ideas Bob,

  

 I will do the AA thing and report back.  Hold off on the  filter for now.

  

 Regarding the wires between the EIS and  sender...

  

 The EIS powers the sender.  Red wire.

  

 The sender gets it's ground from the forest of tabs nearby so  the red/black are not twisted the whole way but this has not changed since day  one.

  

 The white signal wire is twisted with the mix all the way back  to the EIS.

  

 What is the proper way and position to input the ferrite cores  (cylinders)?  Currently I have the cores at the sender with all three wires  going straight through some of the cores, and several times through  others.  6 total.  Each ferrite core reduced the effect an  approximate equal amount from 60 PSI down to 6PSI.  Adding one more  just around the signal wire at the EIS did nothing more.

  

 Bevan



   From:  owner-aeroelectric-list-server(at)matronics.com  [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert  L. Nuckolls, III

Sent: Tuesday, April 12, 2016 2:33 PM

To:  aeroelectric-list(at)matronics.com

Subject: RE: Re: RF  Interference

 

MSP transducers are generally pretty EMC robust. It's  still

a mystery as to what might have changed . . . but

here's an  experiment you can run to help divide

and conquer.



Take an AA alkaline  cell and solder some 'pigtails'

to the + and - terminals. Disconnect the  tranducer

at the engine end of the wiring and hook the

aa battery + to  white, - to black leads running

back to the panel.



Take ferrites off  if convenient . . . 



See what your EIS system reads . . . should

be on  the order of 50 pounds. The key a transmitter

to observe effects.  If  the readings are now steady,

then the interference is upsetting the  transducer.

If the problem persists, then the real victim

is the EIS panel  box. 



I can send you an itty-bitty filter that wires into the  

transducer leads within short distance of the

victim as identified by  experiment . . .

[img]cid:468541322(at)12042016-1608[/img]



What are the wires between the EIS panel  connector

and the transducer? It would be good if they were a

twisted trio  with all panel end wires terminated

at the EIS connector.



 

  Bob . . .

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ceengland7(at)gmail.com
Guest

Posted: Tue Apr 12, 2016 3:16 pm Post subject: RF Interference

 	  Quote: 	
		  I've got a vague memory of guys with top-mounted antennas having 

'issues' with various components in their instrument panels, including 

erratic autopilot behavior. No way to know from here what was actually 

wrong, but it does raise a couple of questions.



Have you tried moving the comm ant feed back to the belly antenna?

(Improperly shielded components in the instrument panel can see a lot 

more RF energy through the canopy than the belly skin.)



Have you verified continuity of the shield on the antenna coax all the 

way to the new antenna, and verified that the shield is properly bonded 

to the skin?

(IIRC, there have been issues with some a/c when the shield didn't get 

properly bonded at the antenna location; basically turned the entire run 

of coax into an RF radiator & gave multiple electronic devices within  

the a/c fits.)

Charlie 	
       

       

       On 4/12/2016 5:21 PM, B Tomm wrote:

     

      	  Quote: 	
		                       Those are excellent             ideas Bob,

        

       I will do the AA thing             and report back.  Hold off on the filter for now.

        

       Regarding the wires             between the EIS and sender...

        

       The EIS powers the             sender.  Red wire.

        

       The sender gets it's             ground from the forest of tabs nearby so the red/black are             not twisted the whole way but this has not changed since day             one.

        

       The white signal wire             is twisted with the mix all the way back to the EIS.

        

       What is the proper way             and position to input the ferrite cores (cylinders)?              Currently I have the cores at the sender with all three             wires going straight through some of the cores, and several             times through others.  6 total.  Each ferrite core reduced             the effect an approximate equal amount from 60 PSI down to             6PSI.  Adding one more just around the signal wire at the             EIS did nothing more.

        

       Bevan

       

                         From:           owner-aeroelectric-list-server(at)matronics.com (owner-aeroelectric-list-server(at)matronics.com)           [mailto:owner-aeroelectric-list-server(at)matronics.com (owner-aeroelectric-list-server(at)matronics.com)] On             Behalf Of Robert L. Nuckolls, III

           Sent: Tuesday, April 12, 2016 2:33 PM

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

           Subject: RE: Re: RF Interference

         

       

       MSP transducers are generally pretty EMC robust.         It's still

         a mystery as to what might have changed . . . but

         here's an experiment you can run to help divide

         and conquer.

         

         Take an AA alkaline cell and solder some 'pigtails'

         to the + and - terminals. Disconnect the tranducer

         at the engine end of the wiring and hook the

         aa battery + to white, - to black leads running

         back to the panel.

         

         Take ferrites off if convenient . . . 

         

         See what your EIS system reads . . . should

         be on the order of 50 pounds. The key a transmitter

         to observe effects.  If the readings are now steady,

         then the interference is upsetting the transducer.

         If the problem persists, then the real victim

         is the EIS panel box. 

         

         I can send you an itty-bitty filter that wires into the 

         transducer leads within short distance of the

         victim as identified by experiment . . .

         

         

         

         

       What are the wires between the EIS panel connector

       and the transducer? It would be good if they were a

       twisted trio with all panel end wires terminated

       at the EIS connector.

       

                

  Bob . . .

fvalarm(at)rapidnet.net
Guest

Posted: Tue Apr 12, 2016 4:05 pm Post subject: RF Interference

That's a very good point Charlie.  I have not checked  continuity of the shield.  However, Comm2 has it's antenna also on the  bottom, and was not changed in anyway during the upgrades.   It has the largest effect. 

  

 I don't think the antennas contact the aircraft skin.   There's a rubber gasket between the skin and the antenna that came with the  antennas.  Further, my aircraft is wrapped in vinyl (since day one) and the  vinyl was applied with the antennas off so that's in between there  too.

  

 Bevan



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

Sent: Tuesday, April 12, 2016 3:47  PM

To: aeroelectric-list(at)matronics.com

Subject: Re:  Re: RF Interference

 

 I've got a vague memory of guys with top-mounted  antennas having 'issues' with various components in their instrument panels,  including erratic autopilot behavior. No way to know from here what was actually  wrong, but it does raise a couple of questions.



Have you tried moving the  comm ant feed back to the belly antenna?

(Improperly shielded components in  the instrument panel can see a lot more RF energy through the canopy than the  belly skin.)



Have you verified continuity of the shield on the antenna  coax all the way to the new antenna, and verified that the shield is properly  bonded to the skin?

(IIRC, there have been issues with some a/c when the  shield didn't get properly bonded at the antenna location; basically turned the  entire run of coax into an RF radiator & gave multiple electronic devices  within  the a/c fits.)

Charlie

On 4/12/2016 5:21 PM,  B Tomm wrote:



  	  Quote: 	
		        Those are excellent ideas Bob,

    

   I will do the AA thing and report back.  Hold off on    the filter for now.

    

   Regarding the wires between the EIS and    sender...

    

   The EIS powers the sender.  Red    wire.

    

   The sender gets it's ground from the forest of tabs nearby    so the red/black are not twisted the whole way but this has not changed since    day one.

    

   The white signal wire is twisted with the mix all the way    back to the EIS.

    

   What is the proper way and position to input the ferrite    cores (cylinders)?  Currently I have the cores at the sender with all    three wires going straight through some of the cores, and several times    through others.  6 total.  Each ferrite core reduced the effect an    approximate equal amount from 60 PSI down to 6PSI.  Adding one more    just around the signal wire at the EIS did nothing more.

    

   Bevan



         From: owner-aeroelectric-list-server(at)matronics.com (owner-aeroelectric-list-server(at)matronics.com)    [mailto:owner-aeroelectric-list-server(at)matronics.com (owner-aeroelectric-list-server(at)matronics.com)]    On Behalf Of Robert L. Nuckolls, III

Sent: Tuesday, April 12,    2016 2:33 PM

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

Subject:    RE: Re: RF Interference

MSP transducers are generally pretty EMC robust. It's still

a    mystery as to what might have changed . . . but

here's an experiment you    can run to help divide

and conquer.



Take an AA alkaline cell and    solder some 'pigtails'

to the + and - terminals. Disconnect the    tranducer

at the engine end of the wiring and hook the

aa battery + to    white, - to black leads running

back to the panel.



Take ferrites off    if convenient . . . 



See what your EIS system reads . . . should

be    on the order of 50 pounds. The key a transmitter

to observe effects.     If the readings are now steady,

then the interference is upsetting the    transducer.

If the problem persists, then the real victim

is the EIS    panel box. 



I can send you an itty-bitty filter that wires into the    

transducer leads within short distance of the

victim as identified by    experiment . . .

[img]cid:328085723(at)12042016-160F[/img]



What are the wires between the EIS panel    connector

and the transducer? It would be good if they were a

twisted    trio with all panel end wires terminated

at the EIS    connector.



   

  Bob . . .

ATT01778.jpg

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158.97 KB

Viewed:

9292 Time(s)

Kellym

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

Posted: Tue Apr 12, 2016 4:27 pm Post subject: RF Interference

Normally com antennas ground via the mounting screws, so it doesn't 

matter if the skin under the antenna is painted, gasketed or whatever. 

Only the counter sink in the antenna and the nutplates and doubler on 

underside need good grounding.



On 4/12/2016 5:01 PM, B Tomm wrote:

 	  Quote: 	
		   That's a very good point Charlie.  I have not checked continuity of the

 shield.  However, Comm2 has it's antenna also on the bottom, and was not

 changed in anyway during the upgrades. It has the largest effect.

 I don't think the antennas contact the aircraft skin. There's a rubber

 gasket between the skin and the antenna that came with the antennas.

 Further, my aircraft is wrapped in vinyl (since day one) and the vinyl

 was applied with the antennas off so that's in between there too.

 Bevan



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

 *From:* owner-aeroelectric-list-server(at)matronics.com

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

 *Charlie England

 *Sent:* Tuesday, April 12, 2016 3:47 PM

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

 *Subject:* Re: Re: RF Interference



 I've got a vague memory of guys with top-mounted antennas having

 'issues' with various components in their instrument panels, including

 erratic autopilot behavior. No way to know from here what was actually

 wrong, but it does raise a couple of questions.



 Have you tried moving the comm ant feed back to the belly antenna?

 (Improperly shielded components in the instrument panel can see a lot

 more RF energy through the canopy than the belly skin.)



 Have you verified continuity of the shield on the antenna coax all the

 way to the new antenna, and verified that the shield is properly bonded

 to the skin?

 (IIRC, there have been issues with some a/c when the shield didn't get

 properly bonded at the antenna location; basically turned the entire run

 of coax into an RF radiator & gave multiple electronic devices within

 the a/c fits.)

 Charlie

 On 4/12/2016 5:21 PM, B Tomm wrote:

> Those are excellent ideas Bob,

> I will do the AA thing and report back.  Hold off on the filter for now.

> Regarding the wires between the EIS and sender...

> The EIS powers the sender.  Red wire.

> The sender gets it's ground from the forest of tabs nearby so the

> red/black are not twisted the whole way but this has not changed since

> day one.

> The white signal wire is twisted with the mix all the way back to the EIS.

> What is the proper way and position to input the ferrite cores

> (cylinders)?  Currently I have the cores at the sender with all three

> wires going straight through some of the cores, and several times

> through others.  6 total.  Each ferrite core reduced the effect an

> approximate equal amount from 60 PSI down to 6PSI.  Adding one more

> just around the signal wire at the EIS did nothing more.

> Bevan

>

> ------------------------------------------------------------------------

> *From:* owner-aeroelectric-list-server(at)matronics.com

> [mailto:owner-aeroelectric-list-server(at)matronics.com] *On Behalf Of

> *Robert L. Nuckolls, III

> *Sent:* Tuesday, April 12, 2016 2:33 PM

> *To:* aeroelectric-list(at)matronics.com

> *Subject:* RE: Re: RF Interference

>

> MSP transducers are generally pretty EMC robust. It's still

> a mystery as to what might have changed . . . but

> here's an experiment you can run to help divide

> and conquer.

>

> Take an AA alkaline cell and solder some 'pigtails'

> to the + and - terminals. Disconnect the tranducer

> at the engine end of the wiring and hook the

> aa battery + to white, - to black leads running

> back to the panel.

>

> Take ferrites off if convenient . . .

>

> See what your EIS system reads . . . should

> be on the order of 50 pounds. The key a transmitter

> to observe effects. If the readings are now steady,

> then the interference is upsetting the transducer.

> If the problem persists, then the real victim

> is the EIS panel box.

>

> I can send you an itty-bitty filter that wires into the

> transducer leads within short distance of the

> victim as identified by experiment . . .

> Emacs!

>

> What are the wires between the EIS panel connector

> and the transducer? It would be good if they were a

> twisted trio with all panel end wires terminated

> at the EIS connector.

>

>   Bob . . .

>

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

toaster73(at)embarqmail.c
Guest

Posted: Tue Apr 12, 2016 6:24 pm Post subject: RF Interference

Bevan,

I have an RV-10 with SL30 (archer wingtip antenna), GNS 430 (belly whip), GRT EIS 6000. I experienced the same effect with my fuel pressure. The 430 only bothered the reading a couple of psi, so I decided that was not giving me a problem. The SL30 shot it up out of limits, so I started chasing the problem. I was able to use one ferrite at the sender in the engine compartment with 2 maybe 3  loops (don't recall exactly) of wire going through the ferrite. I also re-crimped the sl30 coax and reaffirmed the archer antenna connections out on the wing. This seems to have solved my problem to only a few psi on the sl30 transmit and virtually none on the 430. I decided I don't talk long enough for the pressure to rise and grab my attention.

-Chris

N919AR

fvalarm(at)rapidnet.net
Guest

Posted: Tue Apr 12, 2016 7:02 pm Post subject: RF Interference

Thanks Chris!  I have hope.

  

 Bevan



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

Sent: Tuesday, April 12, 2016 7:22 PM

To:  aeroelectric-list(at)matronics.com

Subject: RE: RF  Interference

 

  

  

Bevan, 

I  have an RV-10 with SL30 (archer wingtip antenna), GNS 430 (belly whip), GRT EIS  6000. I experienced the same effect with my fuel pressure. The 430 only bothered  the reading a couple of psi, so I decided that was not giving me a problem. The  SL30 shot it up out of limits, so I started chasing the problem. I was able to  use one ferrite at the sender in the engine compartment with 2 maybe 3   loops (don't recall exactly) of wire going through the ferrite. I also  re-crimped the sl30 coax and reaffirmed the archer antenna connections out on  the wing. This seems to have solved my problem to only a few psi on the sl30  transmit and virtually none on the 430. I decided I don't talk long enough for  the pressure to rise and grab my attention. 

-Chris 

N919AR

bob.verwey(at)gmail.com
Guest

Posted: Tue Apr 12, 2016 9:03 pm Post subject: RF Interference

So is there some archive material which expounds on the use of ferrites and the identification of the correct wire / protagonist (as Bob N likes to refer to it!)

On 13 April 2016 at 04:22, Chris <toaster73(at)embarqmail.com (toaster73(at)embarqmail.com)> wrote:

 	  Quote: 	
		  

Â 

Bevan,

I have an RV-10 with SL30 (archer wingtip antenna), GNS 430 (belly whip), GRT EIS 6000. I experienced the same effect with my fuel pressure. The 430 only bothered the reading a couple of psi, so I decided that was not giving me a problem. The SL30 shot it up out of limits, so I started chasing the problem. I was able to use one ferrite at the sender in the engine compartment with 2 maybe 3 Â loops (don't recall exactly) of wire going through the ferrite. I also re-crimped the sl30 coax and reaffirmed the archer antenna connections out on the wing. This seems to have solved my problem to only a few psi on the sl30 transmit and virtually none on the 430. I decided I don't talk long enough for the pressure to rise and grab my attention.

-Chris

N919AR



	




-- 

Best...Bob Verwey

fvalarm(at)rapidnet.net
Guest

Posted: Thu Apr 14, 2016 12:38 am Post subject: RF Interference

OK,

  

 I have disconnected the output wire at the sender and  connected the positive end of an AA battery to the signal wire going  off to the engine monitor, and batt neg to ground.  I get the appropriate  reading for fuel pressure and NO interference from either  radio.

  

 This tells me that the interference is happening at the  sender.  Still not sure if the interference is arriving at the sender via  the power or ground wires, or just directly through the air.  The  instructions say not to connect directly to 12V as this may damage it. So not  sure how to test for this.

  

 Still puzzled as to why this happened  suddenly.

  

 A new sender has been ordered.  BTW, Mouser.com has them  for half the price of GRT.

  

 Bob, Do you think that the RF filter you offered is  still a valid option?  Is it to protect the sender from failing (where the  sender becomes sensitive to RF as mine appears to have) or just mitigate the RF  from playing games with the senders  electronics?

  

 Bevan



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

Sent: Tuesday, April 12, 2016 10:02 PM

To:  aeroelectric-list(at)matronics.com

Subject: Re: RF  Interference

 

  So is there some archive  material which expounds on the use of ferrites and the identification of the  correct wire / protagonist (as Bob N likes to refer to it!)



 

 On 13 April 2016 at 04:22, Chris <toaster73(at)embarqmail.com (toaster73(at)embarqmail.com)> wrote:

  	  Quote: 	
		           

    

Bevan,   

I    have an RV-10 with SL30 (archer wingtip antenna), GNS 430 (belly whip), GRT    EIS 6000. I experienced the same effect with my fuel pressure. The 430 only    bothered the reading a couple of psi, so I decided that was not giving me a    problem. The SL30 shot it up out of limits, so I started chasing the problem.    I was able to use one ferrite at the sender in the engine compartment with 2    maybe 3  loops (don't recall exactly) of wire going through the ferrite.    I also re-crimped the sl30 coax and reaffirmed the archer antenna connections    out on the wing. This seems to have solved my problem to only a few psi on the    sl30 transmit and virtually none on the 430. I decided I don't talk long    enough for the pressure to rise and grab my  attention.   

-Chris   

N919AR



	




 



-- 

    Best...  Bob Verwey

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Apr 14, 2016 7:38 am Post subject: RF Interference

At 12:01 AM 4/13/2016, you wrote:

  	  Quote: 	
		  So is there some archive material which expounds on the use of ferrites and the identification of the correct wire / protagonist (as Bob N likes to refer to it!) 	


   Actually, it's the antagonist . . . but no . . .

   I'm unaware of any document that leads one

   through the process of adding ferrites to

   system wiring in airplanes.



   These situations illustrate the value of doing

   the homework fo system designers. Here's a

   rough illustration that peeks into the risks

   for living in the wild and wooly world of

   electromagnetic noise.



 [img]cid:.0[/img]



   In aviation, the diagram can be quite simple . . .

   perhaps only three v/a blocks. In a J-3 with no

   electrical system, two of the blocks would be

   a magneto, the third block might be a hand-held

   transceiver. The magnetos would never be victim,

   the hand held never antagonistic. But swap out

   the mags for electronic ignition systems and they

   too are at risk from VHF emissions.



   In the Hawker 4000, there were no doubt hundreds

   of devices. Each one representing the potential for

   being victim, antagonist or both.



   The 'fire walls' are critical components of any

   design intended to thrive in a hostile/vulnerable

   environment. This is what DO-160 testing is all

   about. DO-160 is only one of hundreds of qualification

   protocols . . . each one tailored to a specific

   application.



   Just last week I encountered a toe-stubber

   in my mini-van. My EMS hand-held listens on 463.750 mHz.

   When I got into the car, the receiver squelch opened

   up. The hand-held THOUGHT it was hearing our

   local EMS repeater. After some switch-flipping and

   poking around in the car, I determined that the FM

   radio had a spurious output very near the 463.750

   frequency of interest. It was present no matter

   what mode the radio was in. Turning it completely

   off was the only remedy.

   

   In this case, the propagation mode is clearly

   radiated and a band-aid remedy is probably more

   taxing of time and dollars than to simply replace

   the radio. I'll be installing a panel mounted EMS

   radio in the car pretty soon . . . the radio will

   have to be changed out.



   The replacement radio may also offer unfriendly

   radiations . . . but likelihood of them being

   right on 463.750 are small . . . we shall

   see. At least I can test it on the bench before

   I put it in the car.

   

   Here's a very well executed video on the functionality

   of ferrite beads in the management of hostile

   energy . . .



  https://youtu.be/81C4IfONt3o



   He touches on the use of ferrites on cables

   EXTERNAL to a product . . . I've never seen one on

   a mouse . . . THAT is a really startling example

   of designer malfeasance . . . how hard is it to

   put the fire-wall INSIDE the mouse? I've most

   often seen cable ferrites on VGA monitor signal

   cables. Again, how hard would it be to put the

   fire wall inside the monitor? What's to prevent

   a user from picking up another cable with the right

   connectors with no ferrite bead and suffering

   some EM-Incompatibility effect?



   In the laboratory environment, one expects the

   designers and qualifiers of products to have

   test equipment like that in the video to explore

   vulnerabilities and spurious emissions . . . and

   then add the necessary components to suppress

   undesirable effects to acceptable levels. Often,

   the effect is not driven down to ZERO . . . it's

   just reduced to levels insignificant to reliable

   use of the system.



   This illustrates the small but real risks for

   buying a perfectly good device (like a fuel

   pressure transducer) intended for a low-tech

   terrestrial application only to find that it

   gets fussy when bathed in radio frequency energy

   from an aircraft comm radio.



   The short answer: It's useful to know which fire-wall

   is too short . . . or non-existent. Is it the

   transducer, the panel instrument or perhaps

   both? Then, is there some error of installation

   that compromises the fire wall(s). A common error of

   installation is a disconnected shield in the

   antenna coax of a transmitter that causes the

   feed line to radiate the whole cockpit with RF

   energy that exceeds the height of some system's

   fire wall.



   Fixing the coax shield is easy. But adding height

   to or building a new fire-wall into an already

   installed system is not so easy.



   The ferrite slipped over a wire does what it's

   intended to do . . . put an 'impedance lump'

   in the conductor. As the video showed us, if

   one bead is good, two is better . . . or better

   yet, multiple passes through the ferrite is 

   better still. Inductance goes up as the SQUARE

   of turns.



   The down side of beads-only attempts to fix

   is rooted in the unknown value of a paralleled

   SHUNT effect downstream of the SERIES effects.



 [img]cid:.1[/img]



   In the sketch above, view -A- illustrates the effect

   of adding series impedance on a wire where shunt

   impedances are at best unknown or worst . . . insignificantly

   small.  This is often the case where adding the

   ferrite 'helps a little'.  Ideally, we'd like to see

   a combination of series/shunt effects like -C- or

   even -B-.  The itty-bitty filter I illustrated earlier



 [img]cid:.2[/img]



   has TWO circuits like -B- above with values

   unlikely to upset purely DC signal or power

   paths. However, one would not want to put

   this device in a USB or serial data line . . .

   the components would have deleterious effects

   on the desired signals.



   The nagging unknown about the case under discussion

   is "what changed?"  Knowing that answer would

   probably provide the short-path to a solution.

   Two separate comm systems PLUS a hand-held

   will disturb the victim to varying degrees so

   a broken coax shield ground can be ruled out.



   Given that the affected system was not modified,

   then we're encouraged to explore spontaneous

   changes within the affected system . . . difficult

   to do.  Conversely, we're left with the selection

   and application of band-aids. From a user's

   perspective, a band-aid cure that reduces effects

   to zero meets an operational goal. From an

   engineer's perspective, not knowing the exact

   antagonist->propagation->victim configuration

   is frustrating.



   As I've mentioned before, I've encountered only

   one A>P>V configuration I couldn't fix. Some

   were easy, some rather difficult. In the bureaucratic

   management of solutions within the world of TC

   aircraft, none were very satisfying in that they

   often required a band-aid as opposed to a real

   fix. 



 

 

   Bob . . .

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jluckey(at)pacbell.net
Guest

Posted: Thu Apr 14, 2016 8:59 am Post subject: RF Interference

BobN,



That post is perhaps one of the best primers on EMI I have ever seen.  



Short and sweet with block diagrams & schematics - terrific! 

Thanks for the continuing education

Jeff Luckey



 PS - re your itty-bitty filter:

1. how big is it? perhaps put a penny in the picture

2. when you designed the filter, what frequency are you trying to filter?  I'm guessing it's somewhere in 110-140 MHz but what about harmonics?

3.  are those tiny surface-mount components an inductor & a cap? (or is  it the case that: "you could tell me but then you'd have to kill me?"  







    On Thursday, April 14, 2016 9:16 AM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com> wrote:

     At 12:01 AM 4/13/2016, you wrote:  	  Quote: 	
		  So is there some archive material which expounds on the use of ferrites and the identification of the correct wire / protagonist (as Bob N likes to refer to it!) 	
   Actually, it's the antagonist . . . but no . . .   I'm unaware of any document that leads one   through the process of adding ferrites to   system wiring in airplanes.   These situations illustrate the value of doing   the homework fo system designers. Here's a   rough illustration that peeks into the risks   for living in the wild and wooly world of   electromagnetic noise. [img]cid:.0[/img]   In aviation, the diagram can be quite simple . . .   perhaps only three v/a blocks. In a J-3 with no   electrical system, two of the blocks would be   a magneto, the third block might be a hand-held   transceiver. The magnetos would never be victim,   the hand held never antagonistic. But swap out   the mags for electronic ignition systems and they   too are at risk from VHF emissions.   In the Hawker 4000, there were no doubt hundreds   of devices. Each one representing the potential for   being victim, antagonist or both.   The 'fire walls' are critical components of any   design intended to thrive in a hostile/vulnerable   environment. This is what DO-160 testing is all   about. DO-160 is only one of hundreds of qualification   protocols . . . each one tailored to a specific   application.   Just last week I encountered a toe-stubber   in my mini-van. My EMS hand-held listens on 463.750 mHz.   When I got into the car, the receiver squelch opened   up. The hand-held THOUGHT it was hearing our   local EMS repeater. After some switch-flipping and   poking around in the car, I determined that the FM   radio had a spurious output very near the 463.750   frequency of interest. It was present no matter   what mode the radio was in. Turning it completely   off was the only remedy.      In this case, the propagation mode is clearly   radiated and a band-aid remedy is probably more   taxing of time and dollars than to simply replace   the radio. I'll be installing a panel mounted EMS   radio in the car pretty soon . . . the radio will   have to be changed out.   The replacement radio may also offer unfriendly   radiations . . . but likelihood of them being   right on 463.750 are small . . . we shall   see. At least I can test it on the bench before   I put it in the car.      Here's a very well executed video on the functionality   of ferrite beads in the management of hostile   energy . . .  https://youtu.be/81C4IfONt3o   He touches on the use of ferrites on cables   EXTERNAL to a product . . . I've never seen one on   a mouse . . . THAT is a really startling example   of designer malfeasance . . . how hard is it to   put the fire-wall INSIDE the mouse? I've most   often seen cable ferrites on VGA monitor signal   cables. Again, how hard would it be to put the   fire wall inside the monitor? What's to prevent   a user from picking up another cable with the right   connectors with no ferrite bead and suffering   some EM-Incompatibility effect?   In the laboratory environment, one expects the   designers and qualifiers of products to have   test equipment like that in the video to explore   vulnerabilities and spurious emissions . . . and   then add the necessary components to suppress   undesirable effects to acceptable levels. Often,   the effect is not driven down to ZERO . . . it's   just reduced to levels insignificant to reliable   use of the system.   This illustrates the small but real risks for   buying a perfectly good device (like a fuel   pressure transducer) intended for a low-tech   terrestrial application only to find that it   gets fussy when bathed in radio frequency energy   from an aircraft comm radio.   The short answer: It's useful to know which fire-wall   is too short . . . or non-existent. Is it the   transducer, the panel instrument or perhaps   both? Then, is there some error of installation   that compromises the fire wall(s). A common error of   installation is a disconnected shield in the   antenna coax of a transmitter that causes the   feed line to radiate the whole cockpit with RF   energy that exceeds the height of some system's   fire wall.   Fixing the coax shield is easy. But adding height   to or building a new fire-wall into an already   installed system is not so easy.   The ferrite slipped over a wire does what it's   intended to do . . . put an 'impedance lump'   in the conductor. As the video showed us, if   one bead is good, two is better . . . or better   yet, multiple passes through the ferrite is    better still. Inductance goes up as the SQUARE   of turns.   The down side of beads-only attempts to fix   is rooted in the unknown value of a paralleled   SHUNT effect downstream of the SERIES effects. [img]cid:.1[/img]   In the sketch above, view -A- illustrates the effect   of adding series impedance on a wire where shunt   impedances are at best unknown or worst . . . insignificantly   small.  This is often the case where adding the   ferrite 'helps a little'.  Ideally, we'd like to see   a combination of series/shunt effects like -C- or   even -B-.  The itty-bitty filter I illustrated earlier [img]cid:.2[/img]   has TWO circuits like -B- above with values   unlikely to upset purely DC signal or power   paths. However, one would not want to put   this device in a USB or serial data line . . .   the components would have deleterious effects   on the desired signals.   The nagging unknown about the case under discussion   is "what changed?"  Knowing that answer would   probably provide the short-path to a solution.   Two separate comm systems PLUS a hand-held   will disturb the victim to varying degrees so   a broken coax shield ground can be ruled out.   Given that the affected system was not modified,   then we're encouraged to explore spontaneous   changes within the affected system . . . difficult   to do.  Conversely, we're left with the selection   and application of band-aids. From a user's   perspective, a band-aid cure that reduces effects   to zero meets an operational goal. From an   engineer's perspective, not knowing the exact   antagonist->propagation->victim configuration   is frustrating.   As I've mentioned before, I've encountered only   one A>P>V configuration I couldn't fix. Some   were easy, some rather difficult. In the bureaucratic   management of solutions within the world of TC   aircraft, none were very satisfying in that they   often required a band-aid as opposed to a real   fix.       Bob . . .

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ceengland7(at)gmail.com
Guest

Posted: Thu Apr 14, 2016 9:33 am Post subject: RF Interference

I've got a question about substituting       a battery for the sender's output.

       

       In my (somewhat dim past) experience, the impedance of the line in       question had a major effect on its vulnerability to noise induced       on it. So.... is this a valid test? I'd assume that the internal       impedance of even a AA battery would be much lower than any       electronic sensor normally used around an engine.

       

       On 4/14/2016 3:37 AM, B Tomm wrote:

     

      	  Quote: 	
		                       OK,

        

       I have disconnected             the output wire at the sender and connected the positive end             of an AA battery to the signal wire going off to the engine             monitor, and batt neg to ground.  I get the appropriate             reading for fuel pressure and NO interference from either             radio.

        

       This tells me that the             interference is happening at the sender.  Still not sure if             the interference is arriving at the sender via the power or             ground wires, or just directly through the air.  The             instructions say not to connect directly to 12V as this may             damage it. So not sure how to test for this.

        

       Still puzzled as to             why this happened suddenly.

        

       A new sender has been             ordered.  BTW, Mouser.com has them for half the price of             GRT.

        

       Bob, Do                 you think that the RF filter you offered is still a                 valid option?  Is it to protect the sender from failing                 (where the sender becomes sensitive to RF as mine                 appears to have) or just mitigate the RF from playing                 games with the senders electronics?

        

       Bevan

       

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

           Sent: Tuesday, April 12, 2016 10:02 PM

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

           Subject: Re: RF Interference

         

       

                So is there           some archive material which expounds on the use of ferrites           and the identification of the correct wire / protagonist (as           Bob N likes to refer to it!)

       

       

         On 13 April 2016 at 04:22, Chris <toaster73(at)embarqmail.com (toaster73(at)embarqmail.com)>           wrote:

            	  Quote: 	
		                                               

                  

Bevan,                 

I have an RV-10 with SL30 (archer wingtip                     antenna), GNS 430 (belly whip), GRT EIS 6000. I                     experienced the same effect with my fuel pressure.                     The 430 only bothered the reading a couple of psi,                     so I decided that was not giving me a problem. The                     SL30 shot it up out of limits, so I started chasing                     the problem. I was able to use one ferrite at the                     sender in the engine compartment with 2 maybe 3                      loops (don't recall exactly) of wire going through                     the ferrite. I also re-crimped the sl30 coax and                     reaffirmed the archer antenna connections out on the                     wing. This seems to have solved my problem to only a                     few psi on the sl30 transmit and virtually none on                     the 430. I decided I don't talk long enough for the                     pressure to rise and grab my attention.                 

-Chris                 

N919AR               

             

           	
         

         

                  

         

         -- 

                                                Best...                                    Bob Verwey

yellowduckduo(at)gmail.co
Guest

Posted: Thu Apr 14, 2016 12:03 pm Post subject: RF Interference

I'd guess that the simple battery test confirms it is worth trying the 

filter. The filter might actually have even lower impedance to the 

frequencies of concern.



FWIW I have a plastic body honeywell SS sensor wired with very small 

diameter commercial cable. I don't remember for certain but I think it 

is shielded cable. The cable runs in a bundle with injector and primary 

ignition wires, past the back of my VHF to an EIS4000. I was curious as 

I don't think I've ever watched the pressures while transmitting but I 

just confirmed that transmitting has no effect on either of my SS 

pressure sensors. FWIW I also run the Byonics APRS and have never 

noticed any associated problems with it. I'm delighted with that APRS 

transmitter.  It is probably the only electronic item in the aircraft 

that has run perfectly with no issues at all.



Ken



On 14/04/2016 1:34 PM, Charlie England wrote:

 	  Quote: 	
		   I've got a question about substituting a battery for the sender's output.



 In my (somewhat dim past) experience, the impedance of the line in 

 question had a major effect on its vulnerability to noise induced on 

 it. So.... is this a valid test? I'd assume that the internal 

 impedance of even a AA battery would be much lower than any electronic 

 sensor normally used around an engine.



 On 4/14/2016 3:37 AM, B Tomm wrote:

> OK,

> I have disconnected the output wire at the sender and connected 

> the positive end of an AA battery to the signal wire going off to the 

> engine monitor, and batt neg to ground.  I get the appropriate 

> reading for fuel pressure and NO interference from either radio.

> This tells me that the interference is happening at the sender.  

> Still not sure if the interference is arriving at the sender via the 

> power or ground wires, or just directly through the air. The 

> instructions say not to connect directly to 12V as this may damage 

> it. So not sure how to test for this.

> Still puzzled as to why this happened suddenly.

> A new sender has been ordered.  BTW, Mouser.com has them for half the 

> price of GRT.

> Bob, Do you think that the RF filter you offered is still a valid 

> option?  Is it to protect the sender from failing (where the sender 

> becomes sensitive to RF as mine appears to have) or just mitigate the 

> RF from playing games with the senders electronics?

> Bevan

>

> ------------------------------------------------------------------------

> *From:* owner-aeroelectric-list-server(at)matronics.com 

> [mailto:owner-aeroelectric-list-server(at)matronics.com] *On Behalf Of 

> *Bob Verwey

> *Sent:* Tuesday, April 12, 2016 10:02 PM

> *To:* aeroelectric-list(at)matronics.com

> *Subject:* Re: RF Interference

>

> So is there some archive material which expounds on the use of 

> ferrites and the identification of the correct wire / protagonist (as 

> Bob N likes to refer to it!)

>

> On 13 April 2016 at 04:22, Chris <toaster73(at)embarqmail.com 

> <mailto:toaster73(at)embarqmail.com>> wrote:

>

>     Bevan,

>

>     I have an RV-10 with SL30 (archer wingtip antenna), GNS 430

>     (belly whip), GRT EIS 6000. I experienced the same effect with my

>     fuel pressure. The 430 only bothered the reading a couple of psi,

>     so I decided that was not giving me a problem. The SL30 shot it

>     up out of limits, so I started chasing the problem. I was able to

>     use one ferrite at the sender in the engine compartment with 2

>     maybe 3  loops (don't recall exactly) of wire going through the

>     ferrite. I also re-crimped the sl30 coax and reaffirmed the

>     archer antenna connections out on the wing. This seems to have

>     solved my problem to only a few psi on the sl30 transmit and

>     virtually none on the 430. I decided I don't talk long enough for

>     the pressure to rise and grab my attention.

>

>     -Chris

>

>     N919AR

>

>

> -- 

> Best...

> Bob Verwey

>

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