Light Aircraft Association

Hi

I'm getting airborne radio interference on my Rotax 912s Sportcruiser. I've had a couple of very knowledgeable avionics chaps take a look and they have helped me remove other noise but unfortunately neither have any experience of Rotax's and their ignition and charging systems.

The noise is heard as a sharp buzz when I raise the squelch on my Icom A200. This is a problem as the squelch needs to be set high to remove the noise and the result is poor reception. On my Yaesu handheld using the aircraft antenna I need to raise the squelch as well to remove the noise.

The noise is the same with either mag earthed and also with the charging wires removed from the regulator. I have been told that Rotax noise invariably comes from the charging circuit but I can't see why I am still getting it with the regulator inputs disconnected if that is the case.

I know that the noise is airborne as if I disconnect the radio from the aerial the noise disappears.

Does anyone have any ideas please. I would love to find an avionics engineer that is au-fait with Rotax but they all seem to come from a certified background. I am in the Gatwick area.

Thanks

John,

If you use your handheld with no external antenna connected (just the standard supplied stubby) are you still able to detect the noise?
Just a thought to completely eliminate any "installed wiring" issues.

You may even be able to use your handheld to detect where the noise is coming from.

Tony Nowak

Hi Tony

Yes I still get the interference with a hand held. I have been phoning around to try to find someone who knows about avionics and also Rotax ignition systems. They seem as rare as hens teeth. If you know anyone in the South East I'd love to hear.

thanks
John

I have zero knowledge of Rotax engines!
Perhaps try calling Airbourne Aviation at Popham (01256 398254) to see if they can offer advice or give you contact details of their maint. org. I think all their fleet of aircraft all use the Rotax.
Tony

Do you have a GPS, ipad or similar fitted?
Some GPS when plugged into the aircraft power give noise. It is something to do with the power voltage reduction switching that gives noise or interference. Somebody used to advertise a noise free USB charger for aircraft, perhaps they can advise more.
http://www.microlightforum.com/archive/ ... -5201.html Note that they were getting interference even when on batteries.

I have had a Garmin and a LED landing light that did the same.
If the noise doesnt vary with engine speed, it might not have anything to do with the engine.
Try it with everything else disconnected.

Best wishes
Glen

Check any USB Adapters you have plugged in. I had terrible interference in my vintage aircraft that has no electrical system, just a battery. Nothing could solve noise until I disconnected my iPhone 6 that runs SkyDemon from that adapter. Noise then minimal. I had been running a iPhone 4S on the same socket so can only think the newer iPhone dragged down USB Adapter.
I purchased a Charge 2 from http://www.sync-one2.co.uk/ (Just a customer!)
Works great and no interference.
BTW. You have fitted electrolytic capacitor as required?
Just an idea.
Regards
Gerry

hi

thanks for the advice re the usb chargers. They can give a lot of problems and it is not obvious. Often there is no noise but there is a loss of radio sensitivity. The noise that I have seems to be engine speed sensitive and quite a sharp sound. However disconnecting the alternator connections to the regulator makes no difference.
I am told that this eliminates the charging circuit from being the issue and so it must be ignition.

Have you got it sorted ?
Test run with the "P" or ignition kill wire disconnected at unit end, kill engine by turning fuel off and waiting.
If this stops the nose re rout the kill wires away from any radio power or aerial wire . There is about 40 V AC in those wire when running and it will cause EM interference.


Cheers
Kevin