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Unusual interference

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Old 04-27-2008, 01:33 PM
  #1  
gwheeler
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Default Unusual interference

I recently purchased and built an Aeroworks Edge 540t (46-61) which despite trying two totally separate crystals and receivers still experience unusual interference in the air. Initially there was interference on the ground, but the the antenna was rerouted outside of the fuselage (due to possible interference with the pull pull rudder system) and the ground interference ceased. The plane now seems to perform regular range checks (with the antenna collapsed at 100 feet from all angles) both with the engine on and off, but still goes wild in the air. After three thirty second flights (on separate days) I am left without any ideas on how to proceed.

[ul]
The receivers both have standard length antennas, one has been used in another plane before
The crystals are on channel 11 and 40, one has been used in another plane before
The transmitter works on both those channels
The plane is powered by a saito 1.25
There is no metal to metal contact other than the wheels collars to the axles (with the exception listed below)
The antenna does not touch any other wires and is routed straight to the end of the plane with no folds or knots
Other planes (even on the same channel) fly fine in the same area (which is outside of most city interference)
[/ul]

The only possible cause I can think of is the rudder/steering wheel assembly. There is aluminum to steel (which was assembled according to the ARF instructions). Is there any possibility of aluminum to steel causing interference?

Thanks,
Gary
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Old 04-27-2008, 02:35 PM
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Default RE: Unusual interference


ORIGINAL: gwheeler

I recently purchased and built an Aeroworks Edge 540t (46-61) which despite trying two totally separate crystals and receivers still experience unusual interference in the air. Initially there was interference on the ground, but the the antenna was rerouted outside of the fuselage (due to possible interference with the pull pull rudder system) and the ground interference ceased. The plane now seems to perform regular range checks (with the antenna collapsed at 100 feet from all angles) both with the engine on and off, but still goes wild in the air. After three thirty second flights (on separate days) I am left without any ideas on how to proceed.

[ul]
The receivers both have standard length antennas, one has been used in another plane before
The crystals are on channel 11 and 40, one has been used in another plane before
The transmitter works on both those channels
The plane is powered by a saito 1.25
There is no metal to metal contact other than the wheels collars to the axles (with the exception listed below)
The antenna does not touch any other wires and is routed straight to the end of the plane with no folds or knots
Other planes (even on the same channel) fly fine in the same area (which is outside of most city interference)
[/ul]

The only possible cause I can think of is the rudder/steering wheel assembly. There is aluminum to steel (which was assembled according to the ARF instructions). Is there any possibility of aluminum to steel causing interference?

Thanks,
Gary
I too am experienceing a similar problem with a newly launched GP Super SkyBolt and would love to hear someone answer Gary's problem as well as mine. I have a normal ground range check but when airborne have experienced several hard, elevator (Ch 2) down pulses. I have changed receivers and still experience the same problem. The transmitter works normally on all my other aircraft. The antenna is routed aft in a plastic tube that was pre-installed in the ARF. The receiver and battery are in the exact location as called for in the instruction manual. All pushrods are wire, including two for the evevator that are joined with two wheel collars per the instruction manual. My flying field is remote and I have not experience any interference on this channel in the past on all of my other aircraft. Frankly I am at a complete loss as to the source of the glitch. Ideas anyone??????
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Old 04-27-2008, 08:10 PM
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Default RE: Unusual interference


The only possible cause I can think of is the rudder/steering wheel assembly. There is aluminum to steel (which was assembled according to the ARF instructions). Is there any possibility of aluminum to steel causing interference?
Short answer: If two metal parts can move relative to each other to make-and-break contact, yes it may cause interference.

It's also possible that something else is causing your problem.
Some wild guesses:
Try routing the Rx antenna at an angle away from the fuselage (e.g. to top of vertical fin, or to tip of stab). It's best to avoid positioning the Rx antenna parallel to any other long wires.
If you have long (>10 inches), servo-extension wires, use wire-sets that are twisted together. Twisting the wires together can reduce EMI.
Tx antenna screwed on tight?
Clean off any grease, oil or debris on the collapsible antenna that might be causing intermittent electrical contract between the sliding antenna-sections.
Does your Tx have servo-reversing switches? If yes, you might try cycling the switches a few times to clean the contacts.
Bad/dirty Rx switch, or cracked wire in switch harness-wiring. (happens often)
Cracked/intermittent connection inside battery.

Good luck, hope you find the solution.
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Old 04-28-2008, 09:48 AM
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Rodney
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Default RE: Unusual interference

Do you have a non conducting throttle push rod and no metal to metal in the connection to the throttle arm? Are you using an onboard glow plug igniter? Either of these might cause a problem. I'd still suspect some metal to metal joint vibrating somewhere in/on the plane, especially if the interferance only occurs with the engine running.
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Old 04-28-2008, 10:19 AM
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Default RE: Unusual interference

This response should have been referenced to my own earlier post (3 above) as an additon to that post. Sorry for any confusion, but it seems my problem / question is similar to Gary's and thought someone could shed some light on it.

The throttle push rod is as provided by Great Planes with the ARF. It is steel wire with the supplied nylon clevis at the carb. arm and a brass screw-lock pushrod connector on the servo arm. The photos are from the assembly manual but my plane is set up exactly the same except that I used a new S3004 servo for the throttle and new S3010 servos for the rudder and elevators. I also have the battery and receiver in the reverse of that shown (battery nearest the throttle servo). It is hard to see, but the antenna runs out under the elevator push rods (the ones with the double wheel collars linking them). There must be hundreds of planes with this setup, but I have heard of none with my problem yet.
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Old 04-28-2008, 02:12 PM
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Default RE: Unusual interference

I have nylon clevises on both ends of the throtle linkage. The tail wheel assembly that comes with the plane has alumanum arms with springs that attach directly to the alumanum and a alumanum to metal pivot. I do have a remote glow plug attachment. Thanks for the ideas I will check them out.
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Old 04-28-2008, 04:52 PM
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Default RE: Unusual interference

One comment in your original post concerns me. Are you changing the transmitter crystals? And if so, is the transmitter being retuned after the change?
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Old 04-28-2008, 05:02 PM
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gwheeler
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Default RE: Unusual interference

Thanks for the concern. I have a futaba 9c with adujustable modual. It works fine with other planes that we have on the same frequencies.
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Old 04-28-2008, 10:33 PM
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Default RE: Unusual interference

Ah, ok, I understand. My thought was a poorly tuned transmitter would be putting out a weakened signal and thus could make the receiver more susceptible to any type of interference.
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Old 04-29-2008, 02:12 PM
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Default RE: Unusual interference

Is the landing gear aluminum? Is the receiver antenna routed between them? I had a plane once that I have the receiver antenna routed between the landing gear and experienced glitches in the air.
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Old 04-30-2008, 03:37 AM
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gwheeler
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Default RE: Unusual interference

The receiver and antenna are both behind the landing gear. Thanks for the idea though.
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Old 04-30-2008, 09:37 AM
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Default RE: Unusual interference

A couple more suggestions:

A Hobbico frequency checker is a worthy addition to any field box. Tower has them for $39. It showed me what my glitches were cause from. Looks like ch50 is a bad one at my field. It doesn't sound like it'll fix this problem, but still worth considering, at least you'll know.

I know it's a low wing, but is there a way you can exit the antenna wire immediately out the fuselage and tape it to the tail for testing? Maybe poke a 1/16" hole behind the canopy? Simple is good when your trying to troubleshoot something. Then you can go from there. That way it's parallel to nothing and as far from everything as possible.

Try a different battery and switching the elevator servo with the aileron or throttle servo. It MAY not be a radio problem.
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Old 05-01-2008, 09:49 AM
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Default RE: Unusual interference

Thanks for all of the great ideas. I will be trying them out this weekend when I can range check with the engine running. I an thinking that the remote golw plug or a faulty servo may be to blame at this point. Ken at Aeroworks was also a great help. Thanks to all that posted. I will post the cause when I figure it out.
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Old 05-02-2008, 02:35 PM
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Default RE: Unusual interference

Have you eliminated the Transmitter as a possible source of your problems?

In other words, have you tried another transmitter on a frequency and RX that you know works?

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Old 05-02-2008, 03:13 PM
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Default RE: Unusual interference

Hi gwheeler
I have read all of your posts. Could you please describe, in as much detail as possible, what the plane is doing at the time of the interference, and what it does as a result of the interference.
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Old 05-03-2008, 10:44 PM
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Default RE: Unusual interference

Thanks to all that have posted ideas. I felt that I had eliminated the transmitter as being part of the problem because it works fine with five of our other airplanes at the same field and in one case even with one of the same receivers installed in the plane in question. It is a Futaba 9c that is less than a year old. I have tried it both with the synthesized modual that I normally use and a normal modual with the same results.

When the plane is in the air it gets hit both on the elevator and the aileron surfaces as best as I can tell. So far only 4 flights of about 15 to 30 seconds each. Hits are severe enough to make one want to get back to the ground ASAP. During these brief flights throttle settings range from about half throttle to idle.

Tonight my son was home so we did some more testing on the ground. Removed remote glow adapter -same result. Removed rudder servo from receiver - still interference.
Changed back to channel 11 with RF127DF still glitchy on the ground. With the antenna extended only one or two segments we could not get a clean ground check even with the engine off at 80 to 100 feet.

Fourth week end trying to fly this plane with out success. I have been flying for over thirty years and have never had a problem like this. All of the equipment is new except the one RF127 receiver.

Aeroworks 540t 46-61
Saito 125
Futaba 9c
futaba RF127DF and RF168Df
Channels 11 and 40 both work on other planes at our field
hitec 5645 servos

Any further help would be greatly appreciated.

Thank you
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Old 05-04-2008, 01:30 AM
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Default RE: Unusual interference

Hi GWheeler,

Last stab.... Have you tried replacing all your servos and extensions?

Wouldn't hurt to substitute the battery as well.

Not fun, but it seems you've eliminated everything else.

Quite a mystery. Keep us posted.

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Old 05-04-2008, 06:16 AM
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Default RE: Unusual interference

I had the same problem with a ducted fan jet (BVM Ultraviper). The radio I was using was a Futaba 8UAFS with the standard 8 channel FM receiver.

I tried all, or at least most of, the suggestions already made to no avail. It was a big mystery to me and to everyone else that assisted in trying to solve the problem. Especially because the same receiver was also being used in another DF jet that had the exact same fan unit, engine, pipe, etc., with no problems whatsoever.

I never found what was causing the problem but when I switched to a PCM receiver, the plane flew fine and never experienced another glitch. Problem was undoubtedly masked by the change to PCM.
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Old 05-04-2008, 11:38 PM
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Default RE: Unusual interference

Have you tried a different reciver? some times there are fine cracks in the circut board or peices of trash inside that vibrate around.
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Old 05-05-2008, 12:29 AM
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Default RE: Unusual interference

Thanks to all that have posted ideas to help with my problem. Today I changed some of the servos, the receiver, crystal and used a different receiver and battery and transmitter. Same problem maybe worse. Put original gear back in and rerouted antenna out the top of the plane rather than the bottom and the problem seems to be better. Two successful flights before dark even though the wind was not in our favor. I have many other planes with the antenna routed out the bottom with no problems but if it fixed the problem i am happy.

Thanks again.
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