How to stop ignition interference on radio

Chook

Gold Supporter
Joined
Dec 1, 2019
Messages
40
Location
Perth Australia
Aircraft
Amax single, ELA 07s
So everyone can get an idea what Mosquito owners are up against and why so many have radio issues here is an overview of a common layout. Chuck can let us know how similar his machine is to this. (Chook might cringe when he reads about this layout).

There is no specified radio setup from the factory. Most owners go with a Sirio MD 118-137 antenna (to use without a ground plane) and mount it near the rear end of the helicopters fiberglass tail boom. The most convenient path for the coax cable is then to follow the tail rotor control cable which runs along the tail then down the left side of the engine (very close to the ignition coils) and through to the front of the machine.

For the ignition side the engine setup works like this (this is the XE285 setup, the factory are working on a very different layout they call an XE290). Its a 2 stroke 2 cylinder. The stator in the bottom of the engine is separated electrically into sections to power different functions (one section provides ignition power, another fuel injection power etc..) The unrectified power goes from the stator to the engine ECU (which the factory recommends mounting inside the cabin on the RHS). In the ECU power from each section of the stator (except one) gets separately rectified. The ECU then has built in CDI to drive the ignition coils. The engine has 2 sparkplugs for each cylinder, and has 2 coils per cylinder WIRED IN SERIES (yes, you read that right). The coils get mounted on the engine just below the head. The ECU wiring to the coils runs from inside the cabin on the RHS to the rear LHS of the engine. Its all low grade unshielded automotive wire.
oh shit!!!!
Thanks Grevis. This is not uncommon from manufacturers. Radio it seems is a black art for most.
It would seem there are a few Mosquito owners out there so this investigation could benefit a few which is good.
Also having you in NZ on a closer time zone (Im in Western Australia and not using daylight saving time) is helpful.

Regards...........Chook.
 

Chook

Gold Supporter
Joined
Dec 1, 2019
Messages
40
Location
Perth Australia
Aircraft
Amax single, ELA 07s
Thanks everyone. I printed out every ones suggestions. When the weather warms up a little I will head out to the airport and try one item at a time and log what I do.

I think the main problem might be the wiring. Which I did not do. The headphone jacks are mounted on the rear bulkhead. And the wiring appears to not be shielded.

But I will try Chooks idea first with my hand held from my Gyro. I have the adapter to plug my headset into it. Then I will start the engine with me in the seat and rev the engine. If I hear no noise in my hand held can I assume the problem is in the wiring to the radio.
Sorry no not yet. From what Grevis has just posted regarding his wiring it sounds like there are going to be multiple noise sources.
During your test take particular note of the noises and even background noises. Note their timing eg tick, tick, tick or tick........tick,tick.........tick.
be aware that the initial testing is only looking at the receive section. The transmit is a whole different story but we will do this in a progressive sequence. You may also find that these noises are louder in certain locations in and around your Heli. please make notes so that you are clear.
Oh and do you have the same model number as Grevis. This would be most helpful as he is experiencing good weather at this time.

Regards...........Chook.
 
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