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Interference: replaced everything and still there??

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Old 07-10-2005, 01:20 PM
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Eagle Flyer
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Default Interference: replaced everything and still there??

Running a gasser and all I can get for range test is about 30 feet antenna down and 75 feet up.
PPM
Transmitter works fine on other planes
Have either unhooked or replaced ALL (reciever,servos, switches, batteries, wiring,etc) electronics including the ignition system
replaced spark plug
removed smoke system
no metel to metal contact
nylon type throttle rod
plenty of distance between all radio and ignition components
antenna routeing good, tried different places also

I am currently installing a PCM reciever. I know some will say it only hides the problem, doesn't fix it. But other than changing out the engine I have no options left. Everything else has been done I can think of.

Has any one ever heard of the engine, not the ignition system, causing a radio problem?

Any other ideas???
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Old 07-10-2005, 01:47 PM
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BillS
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Default RE: Interference: replaced everything and still there??

Starter questions. Are you running 6v batteries? When does the interference occur and does it change with engine speed? What type of interference are you getting?

Bill
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Old 07-10-2005, 04:12 PM
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Default RE: Interference: replaced everything and still there??

Include information on what engine/ignition you are using. Pictures of your setup will help too.

We solved a problem on a plane today that had similar problems. It is a RV-4 running a Quadra on magneto ignition. The kill-switch setup was the cause. When we removed it, the problem disappeared. Often these simple things cause huge problems.

It could be that you have a non-resistor type plug or there is a high voltage leak somewhere. Make sure there is no spark leakage on you high tension components.

I had a similar problem with a Zenoah GT80 and CH ignition. The one plug cap was not connected solidly to the spark lead. Once I had replaced the cap the problem was gone.

Spark leakage can often be seen if you run the engine in the dark. Beware of the spinning prop. Have someone helping you when you do these tests.

Hope this helps.

Safe Flying!
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Old 07-10-2005, 04:50 PM
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Default RE: Interference: replaced everything and still there??

I have totally replaced the ignition system, switch,battery, wiring and a complete different ignition unit and resistor plug.
Has a shielded plug cap on both systems. One ignition system came from another plane that had no problems.
All the radio components have either been unhooked or changed out.
I would rather not mention the engine or ignition brand at this time as I don't know if that is the problem or not.
$4.8 battery setup.
Muffler tight.
Removed all unneccessary stuff.
Control linkage has no loose metal on metal hookups.

Just got back from trying the PCM setup. Problem seems to be gone.

I did not remove all the servos. Just unplugged them. Except the throttle I did try a different one on. Can a servo give trouble even though it is unplugged from the reciever?
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Old 07-11-2005, 09:53 AM
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Default RE: Interference: replaced everything and still there??

I had the same sort of a problem. I changed everything and never did find the problem. I put in a PCM receiver and had three times the range with the engine running than I did with the engine not running and the PPM receiver. I went ahead and flew. Yes the problem is still there and I would like to know what it is but PCM lets me go ahead and fly. I don't fly it when there is a lot of people around.
An unplugged servo can't do anything if its not banging up against the receiver or something under vibration
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Old 07-11-2005, 10:14 AM
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Default RE: Interference: replaced everything and still there??

It will be IMPOSSIBLE for us to suggest anything without knowing your setup, make of engine, ignition module, type of switches, length of servo extensions, what airframe, etc. Every combo has its issues, some are apparent, some are not. If you changed "everything" but the engine, then you have found your problem but don't want to see it.


Without complete data we are just poking in the wind.

All other issues aside, if you have any long servo wires running in parallel to your antenna or pull-pull wires, you will have to choke them to reduce RFI. In 100% of the range problems I have seen that did the trick.

That of course is a guess as not knowing anything about the airplane, it can literally be ANYTHING.

DP
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Old 07-15-2005, 09:26 PM
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Default RE: Interference: replaced everything and still there??

It is in a 1/4 scale plane with 605s and 645s in the tail. Long leads, twisted, and with MPI choke extensions. But I did unplug them from 2 different recievers and that didn't help. Still in the plane though. Did not have the wings on so no aileron servos involved. Just the y connector for them which was unplugged from the reciver. I never did remove the tail surfaces servos, except for the throttle that I changed out. The antenna lead has been routed in several ways away from the servo wiring. All switches were unhooked and batteries plugged directly into the reciver and ignition unit. Tried several different battery packs on the radio and ignition. Air frame is a standard wood type arf with Monokote. A very proven model. I did replace the ignitin switch but not the radio switch, though I did unplug it from thr reciever. Maybe it still has a vibration problem on the contacts or in the servos? Maybe I will find time this weekend to remove the last few items and try it again.
But here is the real kicker. It never did range check as good as I thought it should even with the engine off and all of the above mentioned procedures done.
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Old 07-15-2005, 10:48 PM
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Default RE: Interference: replaced everything and still there??

How is the ignition system grounded to the motor? Are there multiple ground connections?

What brand engine?

What radio system and Rx's have been tested?

What is the range, engine off and what height is the antenna during the ground test?

Is the range similar with either Rx?

Have you tried another Tx?
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Old 07-15-2005, 11:16 PM
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Default RE: Interference: replaced everything and still there??

The ignition is grounded by the shielded plug and external braid back to the ignition box. No extra grounds. Mounted in foam. The braid isn't rubbing on anything.
Engine brand, I would not rather say at this time, I don't want to slam a name brand as I can't say yet that the engine is the problem. Same goes for the ignition brand. But both are extremely popular and sucessful.
So far I haven't been able to make any corralation between the problem and RPMs.
I have swapped the whole ignition system out with a known good one. At least it worked on another plane with the same type of reciever, switch,battery etc.
Has had Futaba and Hitec recievers in it. All worked well in other planes.
Transmitter is a Hitec Eclipse with a Spectra module on a known good channel. I have used this TX on a lot of planes and setups before.
Range with the engine off I can't remember for sure. But it should have been more I can say. Antenna all the way down. Even all the way up wasn't good, with the engine off.
Range was the same with different RXs.
The PCM set up is with a new Futaba 9C I just got. Up grading for more model memory. But the Hitec Eclipse has NEVER given me a problem. Actually it has a couple features I like the 9C doesn't have. I upgraded to the 9C with the intention of not needing several TXs I have.
Thanks for the input so far.
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Old 07-15-2005, 11:42 PM
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Default RE: Interference: replaced everything and still there??

To be completely clear the shielded metal plug cap grounds the sparkplug internally and it is grounded to the ignition module only? No other ground connections exist?

Try the Futaba Tx with a PPM Rx, you never know…

It’s unlikely the engine is the problem, especially if it’s an electronic ignition system. The ignition is always a consideration, but today’s modern stuff is good and you mentioned trying a second unit.

Sounds like you have eliminated and or replaced everything? Has any component always been present in the model electrically?

Always run the model up with the wings in place, the wings dampen the engine considerably.
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Old 07-16-2005, 08:50 AM
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Default RE: Interference: replaced everything and still there??

Correct on the ignition. There are no other grounds added. Even though they may help sometimes I realize, they shouldn't be needed if all works correctly. I work with a lot of electronics and know that bad, weak or intermittent grounds can cause all kinds of real weird things to happen.

I may try the Futaba with a PPM if I get time.

Only things always present were the tail surface servos (605s and 645s) and the radio switch. But they were unplugged from the reciever. ???????????

Wings do dampen the plane, but never helped eleviate the troubles.


I think it has Gremlins
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Old 07-17-2005, 02:11 PM
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Default RE: Interference: replaced everything and still there??

Eagle Flyer,

Apparently the interference exists in a complex and expensive airplane and you have considerable effort invested in troubleshooting.

It is a lot of work but I would mount the engine on a test stand. Then I would start removing components from the airplane one at a time and mount on the test rig. Each time a component was moved I would retest. Sometime during the process the problem will be discovered. If the problem is not discovered when finished you might as well be flying the 2 by 4 test rig.

Something about having all the parts out of the airframe often makes the problem easier.

Good luck.

Bill
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Old 07-17-2005, 02:43 PM
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Default RE: Interference: replaced everything and still there??

If I were to add some extra grounds where would you recommend? Alligator clips for temporary testing may work but they in themselves could cause trouble not being tight. And vibrate around or off.
I heard of people adding extra grounds on the ignition system. I think it was from engine frame to battery negative, not sure though.
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Old 07-17-2005, 04:24 PM
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Default RE: Interference: replaced everything and still there??

Additional grounding is undesirable… One ground from the base of the sparkplug to the ignition module housing is best. Multiple grounds are problematic, thus my original inquiry.
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Old 07-17-2005, 04:32 PM
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Default RE: Interference: replaced everything and still there??

As far as I can tell you have thoroughly tested everything. My only suggestion is to return the airplane to the manufacturer and take up R/C boats
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