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  1. #1

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    Gas Engine interference

    Hi guys I am new to gas engine airplanes and I am having a little interference problem. I have a new Sig Arf Extra 300XS and I put in the recommended FPE 2.4 gas engine. This engine has the stock Igniton (Ridge) with the fixed timing. I have a separate 4.8 volt igniton battery and a Life battery for the receiver. I am using an RCXel opto-kill switch and a Spektrum AR7000 receiver and a DX7 Transmitter. My problem is that with the engine running the aileron servos go nuts and I have absolutely no control. The rudder and elevator servos are fine only the ailerons are the problem. I have the receivers more than 10 inches from the igniton and ignition battery I am using twisted extensions on the aileron and other servos and the throttle servo is approximately in line with the aileron servos and it is not glitching at all. All the servos are analog Hitec 645mg. I can't figure out why only the aileron servos are affected. Would changing the ignition to the RCxel igniton help with interference? I was hoping not to have to do that change right away but I can't fly this thing now anyway so if that is the answer then I guess I need to bite the bullet and get that done. Any help would be much appreciated.

  2. #2
    Moderator BarracudaHockey's Avatar
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    RE: Gas Engine interference

    How do you have the aileron servos hooked up to the receiver?

    Twisted extensions don't do anything for interference btw
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  3. #3

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    RE: Gas Engine interference

    The aileron servos are hooked up as flaperons using the aileron and flap channels on the AR7000. I used short 4 inch extensions at the receiver to make it easier to hook up the servos when installing the wing. Each servo also has a 12 inch extension on it to make it reach the fuse/ wing center. I am using HD 20ga. extensions from Taildragger RC. Again the same setup on the elevator and rudder servos with the exception of the length of the extensions.

  4. #4
    Moderator BarracudaHockey's Avatar
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    RE: Gas Engine interference

    Weird. Amplified Y harnesses and that are no-no's on Spektrum system but your setup should work. My guess, since 2.4 really doesn't react to "interference" like that is that you have a vibration problem. The first thing I would try is reseating the connections in the extensions.

    You also might try it with one at a time plugged in.
    Andy - Helicopter Forum Moderator
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  5. #5
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    RE: Gas Engine interference

    Try it without the kill switch. Where are the ignition batteries and ignition switch? They should both be as close to the engine as possible and as far away from any of the RC switches, batteries, wires, etc. Dan.
    Dan

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    RE: Gas Engine interference

    The ignition and ignition battery are under the cowl just behind the firewall but not in the fuselage. The switch and the opto-kill are in the fuselage but opposite side from the receiver switch. I couldn't find a way to mount a switch for the ignition any further away than that. Is it possible that the opto-kill switch could be causing the interference? the opto-kill is strapped to the servo tray area near the receiver battery. But if that were the cause why only the ailerons?

    When I get a chance I will try and run it again with one aileron unplugged to see if anything changes but I find it wierd that both ailerons are affected yet the throttle and the rudder & elevator servos (2) are not affected at all. I have full control of the ailerons without the engine running and absolutely no control with the engine running.

  7. #7
    Moderator BarracudaHockey's Avatar
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    RE: Gas Engine interference

    Yea, I wouldnt get too caught up in where the batteries and switches are, I doubt that's your problem.

    I dont buy the interference thing because everything else is working. I really think you have a vibration issue, a bad plug, bad extension or something of that sort.
    Andy - Helicopter Forum Moderator
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    RE: Gas Engine interference

    I wouldn't worry so much that you only have the problem on the ailerons as much as the fact that you have the problem at all. Mechanical problems and connections aside ( I'll assume they have been checked) I suspect the Ridge ignition and especially that coupled with the Rcexl opto-kill as the source of the problem. As others have said, try removing the kill switch and see if there is a change. From there, I'd replace the Ridge ignition in a heartbeat ... the engine will run better anyway as you'll gain an advance curve in the process. You'll have more power and a smoother idle!

    Of course I assume the obvious things have been checked such as a resistor plug is being used? Any shielding and grounds are connected properly, etc.

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    RE: Gas Engine interference

    Its not unusual at all for ignition noise to just affect one function. The problem could certainly be mechanical in nature though.

  10. #10
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    RE: Gas Engine interference

    suburban, That optical kill switch has brought the radio frequency noise that could be on the ignition line from the ignition battery in close proximity to your RC system. There is no isolation there. You may be coupling right in to your receiver. Remove your kill switch and all its wires and connect your ignition battery straight to the module. This one gives you the isolation you need. The other one does not.Dan.
    http://www.smart-fly.com/Products/Ignition/ignition.htm
    Dan

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    RE: Gas Engine interference


    ORIGINAL: BarracudaHockey

    Weird. Amplified Y harnesses and that are no-no's on Spektrum system but your setup should work. My guess, since 2.4 really doesn't react to ''interference'' like that is that you have a vibration problem. The first thing I would try is reseating the connections in the extensions.

    You also might try it with one at a time plugged in.
    I have to agree with you.
    Try changing the servos.
    It is extremely unusual to have interference on one channel and not the others.
    dirty old men need love too.

  12. #12
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    RE: Gas Engine interference

    Suburban, I think that some pictures would be of benifit but maybe I can add some things to think about. Back in '99 I had a D&B 5.1 twin that Ridge Machine was producing. I was amazed that the engine came with no plug caps at all. Not even rubber ones. What it did come with was silicon plug wires with simple clips ala Briggs and Stratton. So far in this thread there is no mention of plug caps or if you have a resistor plug. In my situation I was getting hit on all channels. I was making things even more difficult because I had set up the airplane with dual FM receivers. The fix was to call Dave Johnson at DA and ask if I could buy some plug caps and wires as at the time he had just released the DA 150. What he did was send me a fried 3W ignition free of charge. I pulled the wires off the Reichmuth ignition and installed the 3W wires and caps. I ran a ground wire fron the braided sheilding to the engine mount. This effevtively grovided grounding as the ignition was built into the mount. Worked like a charm. I don't know what you have but if there is not a metal plug cap could be same situation.


    Ok why you are getting it on the ailerons only. RF is funny stuff and I have seen PHD's get stumped so all I can do is venture an educated guess. Usually when there is RF spillage it is in some kind of pattern. My guess is that the radiating pattern is focused outward but getting larger the further out it gets. Your aileron servo's/leads could be in the radiating pattern. Barracuda looks to be correct that in this case your RX does not seem to be affected but that may be because it's just not in the RF pathway. What I think is happening is your aileron leads are picking up on ignition RF your RX is not affected but the servos are. Twisting wires is as BH stated not a fix but it is a step towards prevention and worth doing. Wrapping the signal wire with the ground wire does provide some shielding but obviously not enough in your case. A fun experiment would be to wrap the leads in aluminum foil and connect the foil to the ground plane of the servo. Before we get too carried away, I am interested in what plug cap you have and if you have a resistor plug or not.

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    RE: Gas Engine interference

    Good post Speedracer!

    I was thinking it but was too lazy to type it! I have seen individual servos be affected by ignition noise in the past. In some cases just moving your hand around the plane while it was running would make the interference come and go.

    And before I get the lecture from someone, yes I know 2.4 GHz. isn't supposed to get interference and I agree it won't from the antenna port. But ignition noise can sure get into the decoder and other slow speed electronics through the back door ..... servo and battery ports. I would suspect even some servos would be affected directly. If it were mine, I'd still replace the ignition even if it didn't produce interference. The engine will run better and total $ spent will probably be less than what the value of the time and $$ spent will be jacking around with a substandard ignition.

  14. #14
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    RE: Gas Engine interference


    ORIGINAL: BarracudaHockey

    Weird. Amplified Y harnesses and that are no-no's on Spektrum system but your setup should work. My guess, since 2.4 really doesn't react to ''interference'' like that is that you have a vibration problem. The first thing I would try is reseating the connections in the extensions.

    You also might try it with one at a time plugged in.
    Hi Andy i'm about to set up a similar ignition system and have never heard of amplified in respect to "y" leads.Is there a thread you could point me to for a good explanation about the ideal set up as i've only run glow engines before.Cheers
    Watch out for the ground eh?

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    RE: Gas Engine interference

    Thanks guys for all the help and information. I won't be able to get back to the plane for a couple of days due to work, family & weather. I will check and replace extensions, and disconnect the Opto kill switch and see if any of those things help. As far as the spark plug goes, I bought the engine used and am using the plug that was in the engine when I got it, so I am not sure if it is a resistor plug but I will replace it just to be sure. As far as the ignition goes it is one of those that does not have a spark plug boot just a silicone spark plug wire with the Briggs & Stratton type plug connector. The ignition does have a ground wire that is connected to one of the engine mounting bolts so it is grounded in that respect. I did ask about that type of ignition either here on RCU or somewhere else and was told that it would be fine but I still have my doubts. I will be upgrading to the RCXel ignition but that probably won't be till the winter now. At any rate thanks for all the responses and I will post back once I have a chance to work more on this issue and if I find anything. I probably won't fly this plane till I get the new ignition even if I find the problem. I am also planning on changing the receiver just to see if it might be something in there (bad solder joint or something).

    Thanks again for all the help.

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    RE: Gas Engine interference

    Amplified extensions are used for long runs of wire in the large airframes. They aren't needed in 99% of the planes. Especially now that people are running higher voltages and larger gauge wire, etc. They are suppposed to make up for signal loss and reduce cross coupling in the wires in long runs to the servos in 40%ers and the big gliders, etc. I've never used them.

  17. #17
    Moderator BarracudaHockey's Avatar
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    RE: Gas Engine interference

    Yes, reversing Y's and servo extensions with amplifiers are a no-no for Spektrum 2.4 installations.

    Twisting servo wires does nothing.

    Twisting pairs of communication cables is a different story but thats not applicable to what we are doing.
    Andy - Helicopter Forum Moderator
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    RE: Gas Engine interference


    ORIGINAL: BarracudaHockey

    Yes, reversing Y's and servo extensions with amplifiers are a no-no for Spektrum 2.4 installations.

    Twisting servo wires does nothing.

    Twisting pairs of communication cables is a different story but thats not applicable to what we are doing.

    are you saying these by futaba,Futaba SR-10 Dual Servo Reverse

    http://www3.towerhobbies.com/cgi-bin...?&I=LXANF2&P=7

    can not be used on a spektrum system?

  19. #19
    Moderator BarracudaHockey's Avatar
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    Andy - Helicopter Forum Moderator
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  20. #20

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    RE: Gas Engine interference

    Just a note and probably not the problem, but double check the balance of the prop both horizontal and vertical.

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    RE: Gas Engine interference

    Had a similar problem but I was on FM. I removed the kill switch and problem went away.

  22. #22
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    RE: Gas Engine interference

    Both JR and Spektrum specifically warn against using "Y"s and reversing Y's in the 2.4GhZ systems.

    Twisting wires does help with a number of RF issues. There may be some they don't protect against. That doesn't mean it isn't worth using them. Cover as many bases as you can.

    As Jim Rice used to say, "There are about a thousand things that can knock your plane from the sky. Once I've done everything I possibly can to prevent them, I figure I've covered about six hundred and fifty of them."

    I've seen RF noise affect ALL the servos, and I've seen it affect just one servo. I've helped solve the problems, and I've been there when we couldn't solve it.

    It's definitely one of the tougher things to troubleshoot. I do believe that a particular RF noise can emit a frequency specific to one channel. It's certainly possible.

    Though I've dealt with a fair amount of these problems, I'm no expert and I've been beat by it on occasion. I can only go on instinct here. I'm inclined to look at these things, in this order: 1 - remove the kill switch and try it (that's free). 2 - spark plug (cheap, quick and easy to change and check). 3 - spark plug cable and shielding (most likely the culprit, but considerably tougher to change than a spark plug).

    I hope this helps in some way.

    Good luck!

    ~ Jim ~[8D]
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    RE: Gas Engine interference

    (Both JR and Spektrum specifically warn against using "Y"s and reversing Y's in the 2.4GhZ systems.)

    AH, this is interesting, I have used 2 of them for years on my spektrum 2.4, I never read any warnings on the Futaba site about this, guess I looked under the wrong rock!

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    RE: Gas Engine interference

    Twisting leads is to suppress crosstalk between lines or to prevent Electra magnetic coupling (EMC). It is no help for RFI. Since there are no other lines near the aileron lines or the lines are not near a motor or generator, twisting is pointless.
    dirty old men need love too.

  25. #25

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    RE: Gas Engine interference

    Twisting looks nice! I guess that is a purpose.


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