REFLECTOR: Ignition Noise

Michael Watson mikewatsspg at gmail.com
Wed Jun 13 16:27:21 CDT 2007


Hi Ron,

I have been following this thread form the beginning,
Your problem does not seem to be a power or ground
induced noise. It seems that some harmonic of the noise
frequency generated by your EIS, is being picked up by
your antenna  and the  430 ANL circuits is not filtering
it out. ("IF I DISCONNECT THE COM ANTENNA, THE NOISE STOPS")
Your Microair 760 may be cheaper but has a better ANL circuit.

Where did you connect the portable antenna. directly to the rear of the
radio,
or the connector between the wing and strake ?

I would contact Garmin and find out if there is any way to increase the
sensitivity of their ANL circuit.


On 6/13/07, Ron Brown <romott at roadrunner.com> wrote:
>
>
> I have resumarized the problem and trouble shooting to make the reading
> (and your suggestions easier):
>
>  The PROBLEM:
>
> Spark plug noise on the Garmin 430 audio out to the headphones.  No noise
> on the #2 COM which is a Microair 760.  Noise increases in frequency (twice
> engine RPM) as engine RPM is increased.  Noise goes away when the Jeff Rose
> Electroair Electronic Ignition system is turned off.  Noise also goes away
> when the COM antenna is disconnected from the Garmin 430.  The noise
> continues when the PS4000 Intercom/Audio panel is turned off.  The noise is
> also evident on the Garmin's NAV Audio.  Spark noise can be heard on a Radio
> Shack portable scanner.  The noise has been there for quite a while - but in
> the past it always improved after a few minutes to the point it was not a
> nuisance after a few minutes of running.  But now the noise is continuous.
> By the way, the noise does not break the automatic squelch - but can be
> heard when a distant transmitter breaks squelch or the auto squelch turned
> off on the Garmin.
>
> Other info about the system.  Velocity with Lycoming IO 360 flying for 350
> hours.  Slick magneto and Jeff Rose Electroair Electronic Ignition.  The
> ignition power goes down the right duct with the other noisy wires such as
> the 4 ga main feed to the starter and alternator and the copper ground
> tubing vacuum line .  My headphone connections are in the keel behind the
> seats.  The headset jacks are grounded only at the Audio Panel.  My antenna
> wires run down either side of the fuselage just above the floor ducts.
>
> All of my instrument panel grounds are to a single point - ground bus bar
> which is connected to the negative side of the battery.  The avionics are
> fed off an avionics bus which can be fed off of the main power bus or
> directly from the battery (an implementation of Nuckolls essential bus).
> There is a diode between the main bus and the essential bus which prevents
> the main bus from dragging down the essential bus.
>
>
> The TROUBLESHOOTING:
>
>
>    1. Swapped COM Antennas, connected a portable antenna
>    2. Swapped headphones.
>    3. Installed balluns on the COM antenna wire.
>    4. Swapped Garmin 430's with a friend.
>    5. Installed new REM37BY Autolite spark plugs
>    6. Installed new radio resistance spark plug wires from Electroair
>    7. Powered the Garmin from a 2nd battery, installed a Radio Shack
>    noise filter (choke and capacitor).
>    8. Checked grounds (cleaned and retightened) at EI and central
>    ground bus at instrument panel
>    9. Checked grounds for the power going to the EI.  It was grounded
>    on both ends, lifted the ground at the panel - no effect.
>    10. Powered the EI via a twisted pair cable connected to a
>    2nd battery.
>    11. Installed a Radio Shack noise filter (choke and capacitor) on
>    the EI power input.
>    12. Replaced the direct fire coils (NAPA IC39SB - same as used on
>    Pontiac and Buick auto engines)
>    13. removed the EI timing head so that I could spin it and make
>    sparks while the engine was not running looking/listening for spark jumping
>    anywhere, none found.
>    14. Replaced one plug wire at a time then checked for noise while
>    spinning timing head.  No change.
>
> I can't think of anything else to try other than replacing the EI with a
> Slick magneto - ain't going to happen!
>
> Any and all ideas WELCOMED!!!!
>
> THANKS!
> Ronnie Brown
> Velocity 173 Elite RG Lycoming IO360
>
>
>
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-- 
Mike W.
1997 Velocity Elite RG
Franklin /IVO Electric CS
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