REFLECTOR: Ignition Noise

Tue Jun 12 23:59:04 CDT 2007

Ronnie...

Two questions

Have you had the noise all the time or did it just crop up... And, can you 
move the EI unit off the firewall just for a test to see if it is just to 
close to the radio itself...???  2 amps X 25000 volts = 50,000 watts..... 
That's as much as some radio stations...  I think...

Best... Steve

----Original Message Follows----
From: "Ron Brown" <romott at roadrunner.com>
Reply-To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
CC: aeroelectric-list at matronics.com
Subject: Re: REFLECTOR: Ignition Noise
Date: Tue, 12 Jun 2007 20:56:00 -0400

Sorry, Brian, No Beer tonight!!!

I have worked all day chasing the noise problem on my Garmin 430:

Disconnected the shield for the power to the EI at the instrument panel (it
was indeed grounded on both ends), found a loose ground wire on the single
point grounding terminal block on the panel; ran the Jeff Rose EI off an
independent battery, using a separate twisted wire, grounded only at the
Electronic Ignition end; installed a big capacitor at the EI end of the
power wire, installed the Radio Shack inductive noise filter kit  swapped
out the direct fire coils (NAPA IC39SB); replaced one plug wire at a time,
removed the EI timing head so that I could spin it and make sparks while the
engine was not running looking for spark jumping anywhere, none found.

I'm tired - I think I'll drink the beer that I was going to send you - and
go to bed and sleep on it!!!  (and copy the Aeroelectric list and see if
anyone else has any suggestions short of replacing the EI with a Slick -
ain't going there!!!!)

ARRGGHHHHH!!!

Ronnie Brown
Velocity 173 Elite RG - IO360 Lycoming

----- Original Message -----
From: "michalk" <michalk at awpi.com>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Monday, June 11, 2007 3:21 PM
Subject: Re: REFLECTOR: Ignition Noise

"power for the EI is in a shielded wire"
"the EI is grounded on the firewall"

Do you mean that your power path to the EI is battery->panel switch->EI?
   And that this wire is a single conductor shielded wire?

How does your firewall ground return to the battery?  If you patch in a
battery to your EI and do not send this power down the duct, does that
solve the problem?

You have two problems.  First, your 430 is a receiver of this noise, and
second, your EI is generating this noise.

Fixing the noise generator usually makes other things work better, so
start there.  The EI may have a large dV/dT, meaning a large voltage
spike in a short time causes magnetic flux lines and electrical fields
to be coupled into other things.

If your shield is connected in two places, remove the one closest to
your instrument panel.  If the noise goes away, good, but you still have
a problem.  The EI sent current down that shield because its a least
path of resistance back to your battery.  Impedance goes up as frequency
goes up ... not just resistance.  Your EI will be much happier giving
you a stronger spark if you fix the root cause of your problem.  Look at
your ground path.  No need really for shielded wires.  The real need is
to have your power and ground wires twisted.  Shielding is for
capacitive noise.  If your power is balanced (no common mode noise) then
there is no energy to capacitively couple.  Most likely you are
magnetically coupling the noise.

Don't fix the symptom, fix the problem.  Use twisted wire, and if you
still want shielded, shield it at the EI(the radiator), not at the
instrument panel.  Try to not ground your EI power to the firewall.
Even if the ground is attached to the firewall, the electricity will
like that path better, resulting in lower noise.

I'll bet you a beer that will fix it.

Ronnie Brown wrote:
 > The headsets are grounded at the PS4000 intercom and no where else (but I
 > will verify)  The head set wiring is through the keel, EI is powered and
 > grounded through the right side duct.  Power for the EI is in a shielded
 > wire and the shielded wire is grounded at the mag - by way of the panel.
 > Now that I think of it, the EI shield is grounded twice!  Might need to
 > lift
 > one end.  Hmmm - thanks for the suggestions, Brian!
 >
 > The EI is grounded on the SS firewall as well as to the engine (but not
 > using a braided wire - wonder if that would help?)
 >
 > Ron
 >
 > ----- Original Message -----
 > From: "michalk" <michalk at awpi.com>
 > To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
 > Sent: Monday, June 11, 2007 2:12 PM
 > Subject: Re: REFLECTOR: Ignition Noise
 >
 >
 > It's not a high frequency coupling.
 >
 > I would guess that your antenna shield is a ground path for your EI.
 > Are your headset jacks insulated from the instrument panel?  Or, do your
 > headset wires share a common ground with your EI?
 >
 > Ron Brown wrote:
 >> Actually, I have been chasing a spark noise in my Garmin 430 for a
 >> several weeks.  It is only coming in the 430, it goes away when I turn
 >> off the Jeff Rose Electroair electronic ignition, it changes frequency
 >> with engine RPM, it does not come in to the #2 com which is a lowly
 >> Microair 760, it does not make noise if the antenna is disconnected from
 >> the 430.  Arrrggghhh!
 >>
 >> I have changed antennas from right to left, used a portable antenna,
 >> bought new plugs and plug  wires, connected the 430 to a separate
 >> battery, swapped 430's with a friend, removed ground wires, cleaned and
 >> retightened them, installed noise filters on the 430 and Electroair,
 >> removed and inspected new plugs and new wires.  Next I am going to
 >> remove the timing unit from the distributor hole, spin the unit and see
 >> if I can hear sparks, then try  replace one high energy coil at a time.
 >>
 >> We are planning to fly to Colorado next week and I sure would like to
 >> NOT hear sparking noises when I am receiving a far away aircraft or ATC.
 >>
 >> Any other suggestions from the collective???
 >> Ronnie

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