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Thor 45 Radio Interference

Old 02-02-2014, 04:47 AM
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yak86
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Default Thor 45 Radio Interference

I have a Thor 45, the engine runs awesome. starts second flip, idles just right, runs up fine. But its giving me radio inference; sometimes my one flap will jump or something odd like that.

I'm using a jr 9ch 2.4, I have everything separated in the plane. I was thinking about swapping out the ignition for a rcexl and see if that fixes it. But for 70 bucks I could put that twords a dle55 and call it a day. what do you guys think?
Old 02-02-2014, 06:05 AM
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earlwb
 
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Is your spark plug cap on tight? Most spark plug caps are a twist lock design, you need to push down on it, and give the cap a twist to lock it in place. A loose spark plug cap usually causes these problems. A worn out, damaged or broken spark plug cap can do it too.

Another thought is if you are using a resistor spark plug or not. I don't know if the Thor OEM ignition unit has a resistor built into the ignition unit or not, so it may need a resistor spark plug.

Then is the ignition unit grounded to the engine OK or not. Most modern ignition modules use a sheiled braid spark plug wire that grounds the spark plug to the ignition module. But the braid can become damaged or loose or broken away from the spark plug cap. Other older systems used a unshielded spark plug wire and a ground wire going to the engine.

Last edited by earlwb; 02-02-2014 at 06:09 AM. Reason: add more info
Old 02-02-2014, 07:49 AM
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dirtybird
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I seriously doubt that you have an interference problem.
I once ran an experiment. I drove an ignition unit with a function generator and held the exposed spark plug right next to the 2.4 system antenna. It showed no response.
When you bind the receiver sends a code to the transmitter. After that the receiver will only accept that code. The spark from your spark plug does not have that code. The only way the spark could interfere is if it completely swamped the band. Then you receiver would shut down.
Look for vibration problems.
Also look for reflections from metal objects. Reflections have the code.
The wavelength of 2.4G is slightly more than 10cm. A 1/2 wavelength is about 5cm or 2" So if your motor is about 2" from your 2.4 antenna, you could have interference. You will not notice this while flying because the angle is constantly changing. It has to be at the exact angle to cause interference

Last edited by dirtybird; 02-02-2014 at 08:01 AM.
Old 02-02-2014, 11:27 AM
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I think I would use the $70 as a down payment on a DLE. It will just be something else later on if you put a new ignition on it.
Old 02-02-2014, 07:33 PM
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ec121
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A cheap ignition can cause 2.4 interference. It happened to me until I made an ignition cover out of a tin can and grounded the cover to the engine with a wire. Use the magnetic type of can. My plane would almost jump inverted on 2.4 until I did that. After the shielding there was no more EMI. It was one of those cheap, blue plastic ignitions that came with the 50cc XYZ engines. Had it on a Kangke Extra.
Old 02-02-2014, 08:26 PM
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dirtybird
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It was one of those cheap blue ignitions I ran my test with.
You can get interference thru the servo leads.Direct to the servo.
Cheap servos do not have proper bypass systems.
Old 02-03-2014, 04:14 PM
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yak86
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The plug cap is tight on the plug. I might swap out the throttle servo, its the only part of the rx system thats close to the engine. Would a digital servo help?
Old 02-03-2014, 07:32 PM
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ec121
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Don't know about the digital servos. The signal decoder part of the servo is probably the same. Just the motor driver part is digital. I had a 3W 85cc twin ignition go bad on one side, and it burnt up the servos. I could even hang a loose servo on a servo tester and battery down beside the installed throttle servo and they would both jump. The bad ignition made the servos jump so much they quit. It finally went all the way out and I bought an RCEXL replacement to fix it.
Old 02-04-2014, 05:23 AM
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yak86
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Ill prob just change out to a RCEXL ignition, I think there like 75 bucks from valleyviewrc. Thanks for your help everyone.
Old 02-04-2014, 06:39 AM
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The signal decoder in a digital servo is in fact quite different than an analog servo.
I surely would try a digital servo before I bought a new ignition.
Old 02-04-2014, 11:22 AM
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Originally Posted by dirtybird View Post
The signal decoder in a digital servo is in fact quite different than an analog servo.
I surely would try a digital servo before I bought a new ignition.

Ill have to give that a try.

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