REFLECTOR: Ignition noise
Brian Michalk
michalk at awpi.com
Wed Jun 13 22:04:31 CDT 2007
Okay. This is new information.
When you take the rubber ducky off the RG58, the noise stops.
This sounds like electromagnetic coupling. I could be wrong as I'm
thinking to myself, but what else could it be?
Rubber Ducky ... no ground plane.
If you point it right at the EI, does the noise level go down? Right
out the top of the antenna should be a low gain area.
If you remove the Rubber ducky, then short across the center conductor
to shield, does the noise go away? If yes, then it's definitely coming
in through the antenna. If no, then it is probably getting coupled to
the shield somewhere.
I forgot you mentioned you have an oscilloscope.
There are several things you could do.
1) Make a dipole antenna like rabbit ears. Use that as a probe to try
and locate the source.
2) Make a coil and connect each end to your scope. Kinda like a
microphone. Use that as a probe.
If the noise is coming from plug wires, and your system is wasted
spark: For testing, run the first cylinder and the third firing
cylinder (one compression while other on exhaust) plug wires right next
to each other and also make sure the bases of the plugs are electrically
connected. This should minimize radiation from the wires. If you still
have noise, this is not where it's coming from. These two plugs fire at
the same time. As I previously explained, the current goes down one
plug wire and back on the other.
You already mentioned installing resistance wires. I'm running out of idea.
You can also use your scope in the same manner as the DVM test. Maybe
you'll see your voltage drops with a coupled waveform.
Ron Brown wrote:
> I can disconnect the antenna from the back of the 430, or disconnect
> at the wing - both cases the noise goes away. If I connect the
> portable antenna with a length of RG58, I get the noise. If I take the
> rubber ducky antenna off the RG 58 the noise stops, so it is
> definitely coming in the receiver of the 430 and not getting trapped
> out like it does with the Microair.
>
> Today I went up to the hangar to verify the grounding. Sure enough,
> although my DVM shows a very low resistance, 0.1 ohm, it showed a 60
> milivolt difference between battery ground and the 430's case or the
> ground bus which is next to it. I cleaned terminals and got this down
> to 11 mv and I thought - OK this is it! But cranked her up and still
> clicking - just keeps on clicking!
>
> Tomorrow I am going to check grounds from nose to tail using Brian's
> suggestion - looking for voltage drops and trying to clean each one
> up. I have improved one problem - occasionally I would get a low
> voltage alarm -11.5 volts when the gear was being retracted. Most of
> the time, voltage only drops a few tenths.
>
> Still looking!!!
> Ronnie
>
>
> ----- Original Message -----
> *From:* Michael Watson <mailto:mikewatsspg at gmail.com>
> *To:* Velocity Aircraft Owners and Builders list
> <mailto:reflector at tvbf.org>
> *Sent:* Wednesday, June 13, 2007 5:27 PM
> *Subject:* Re: REFLECTOR: Ignition Noise
>
> 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
> <mailto: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
>
>
>
> _______________________________________________
> To change your email address, visit
> http://www.tvbf.org/mailman/listinfo/reflector
> <http://www.tvbf.org/mailman/listinfo/reflector>
>
> Visit the gallery! www.tvbf.org/gallery
> <http://www.tvbf.org/gallery>
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> <http://www.tvbf.org/pipermail>
> Check old archives:
> http://www.tvbf.org/archives/velocity/maillist.html
>
>
>
>
> --
> Mike W.
> 1997 Velocity Elite RG
> Franklin /IVO Electric CS
>
> ------------------------------------------------------------------------
> _______________________________________________
> To change your email address, visit
> http://www.tvbf.org/mailman/listinfo/reflector
>
> Visit the gallery! www.tvbf.org/gallery
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives:
> http://www.tvbf.org/archives/velocity/maillist.html
>
>------------------------------------------------------------------------
>
>_______________________________________________
>To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>
>Visit the gallery! www.tvbf.org/gallery
>user:pw = tvbf:jamaicangoose
>Check new archives: www.tvbf.org/pipermail
>Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>
More information about the Reflector
mailing list