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the twilight zone ?

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Old 06-07-2007, 09:12 PM
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Default the twilight zone ?

Hello all , I just got back from the field about 1 hour ago. A guy was experiencing some freekish interference. Please let me explain.

With his radio on , receiver on, him , me and four other guys was able to wave our hands over the radio which would cause one aileron to move to an up position. When the transmitter was in his hands, even with the antenna down , there was absolutely no interference. We fooled with this for about thirty minutes and the same results occured.

He is using a 5 cell RX pack, and a 11.1v lipo fopr the TX. The conclusion I came up with is the Lipo pack is sending a false signal to the channel of the aileron in question. When this interference happens the TX is about one foot away from the RX. He hovers close to himself and really needs to find out what is going on.

Thanks for all of your replies.

DJ
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Old 06-07-2007, 10:03 PM
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aussiesteve
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Default RE: the twilight zone ?

A couple of questions
Did it do it with the Tx further away (Maybe 1 metre or more?).
Was the set up under cover at the time?

I have a JR radio (PCM9X) that does some really weird things like that when it is right next to the plane - especially if it is under cover (a tin roof) or indoors. Can't explain it, The radio has been thoroughly checked out a couple of times and if it is a metre or so away it is never a problem. Luckily it's never affected the throttle channel but on one plane it affects the elevator and the other it affects the ailerons. I'm also running a regulated LiPo Tx pack in it so I'll be interested in the replies on this too.
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Old 06-07-2007, 10:11 PM
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Chris Moon
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Default RE: the twilight zone ?

I would bet that the problem is related to RF getting into the extensions. Had the same problem- even with a dual conversion receiver. It is like the Rf interferes with the signal that is sent from the receiver to the individual servo and makes it do funny stuff. Replaced the cheapie extensions with "genuine" gold plated connectors and the problem was nearly eliminated. Replaced the "genuine" extensions with twisted ones from AirWild and never saw the problem again. I think the problem is worse if you are using digital servos but in any case, the twisted extensions fixed it for me.
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Old 06-07-2007, 10:11 PM
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Default RE: the twilight zone ?

no it isn't under cover, and as soon as he grabs the radio the problem disappears. Remember , your body acts as an antenna like it or not . I have not tried this with my radio but I was using a lipo for a week or so until I left the radio on and that killed the lipo and the concept of using lipos. He is using a Fataba 9c. I thinkl the servos are digital , but if they are why does only one flip out ?
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Old 06-08-2007, 12:48 AM
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Default RE: the twilight zone ?

I think you body acts as the "ground" for the transmitter. Where was the Transmitter when this happened?. Was it on a wooden table?.
if so it was not grounded.

regards

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Old 06-08-2007, 01:08 AM
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Default RE: the twilight zone ?

Good Point Tom
Mine's only ever done it when the TX was on a wood table or indoors when I'm setting up a plane. Never made that connection before. (pardon the pun - it's unintentional).
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Old 06-08-2007, 04:06 AM
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Default RE: the twilight zone ?


ORIGINAL: TommyWatson

I think you body acts as the "ground" for the transmitter. Where was the Transmitter when this happened?. Was it on a wooden table?.
if so it was not grounded.

regards


This is quite agreeable , but why does only one servo move when we wave our hand over the TX ? And yes it is on a wooden table use for starting the engines.

DJ
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Old 06-08-2007, 07:15 AM
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Default RE: the twilight zone ?

Is it a PCM or PPM radio?. There may be some distortion of the signal or multi-path reception happening when you pass your hand over the ungrounded TX. I don't think PCM would do it but PPM and am might. I am no RF expert but someone else might know for sure.

I will try my PCM and PPM sets and see if I can duplicate the "Twilight Zone"

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Old 06-08-2007, 11:29 AM
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Default RE: the twilight zone ?

What happens when you plug that aileron servo into another channel?
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Old 06-08-2007, 07:51 PM
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Default RE: the twilight zone ?

Hello all , I just got back from the field and the guy wasn't there. I am not sure whether the radio is ppm or pcm but regardless this type of interference should not happen with either. Keep in mind the right aileron or left depending on how you look at the plane moves to it's futher end point and holds there until the hand waving over the TX is removed. This isn't just a little bit of flutter.

DJ
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Old 06-08-2007, 09:48 PM
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Default RE: the twilight zone ?

I've seen some wierd stuff with noisy servos. Example, PPM electric with 4 micro servos (Typhoon 3D standards, aka cheap) Terrible interference when I got 30 feet away. After eliminating every other thing (RX, crystal, motor and ESC) I noticed that I could get further away with every servo I unplugged. I ended up replacing them all with Hitec 55's, annd itis now solid as a rock.

I think you may have a bad servo, or the channel on the RX is funky. You could also be 'swamping' the RX. What happens when you do just a normal range check?
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Old 06-08-2007, 09:51 PM
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Default RE: the twilight zone ?

Range check is rock solid. I suspect the servo also because it is using a phantom signal to move .


DJ
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Old 06-09-2007, 12:45 AM
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Default RE: the twilight zone ?

sometimes, with a nicad battery, when the battery was fresh off the charger, tx batt that is, this same thing would occur when the tx antenna was too close to the rx.
it is called swamping.
i am betting that your lipo set up is giving enough more constant voltage above 9.6 to the system that it is able to overdrive the output of the rf board a tad.
would not worry about this, unless it continued even after moving the tx 2-3 ft from the rx.
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Old 06-09-2007, 05:57 AM
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Default RE: the twilight zone ?


ORIGINAL: mongo

sometimes, with a nicad battery, when the battery was fresh off the charger, tx batt that is, this same thing would occur when the tx antenna was too close to the rx.
it is called swamping.
i am betting that your lipo set up is giving enough more constant voltage above 9.6 to the system that it is able to overdrive the output of the rf board a tad.
would not worry about this, unless it continued even after moving the tx 2-3 ft from the rx.

the lipo battery was one of my guesses also. His voltage reading at the time was a rock solid 12vdc, and I told him to try a regular NiMhd or a NiCd battery to see if the houdini movement would stop.


DJ
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Old 06-09-2007, 09:13 AM
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Default RE: the twilight zone ?


ORIGINAL: mongo

sometimes, with a nicad battery, when the battery was fresh off the charger, tx batt that is, this same thing would occur when the tx antenna was too close to the rx.
it is called swamping.
i am betting that your lipo set up is giving enough more constant voltage above 9.6 to the system that it is able to overdrive the output of the rf board a tad.
would not worry about this, unless it continued even after moving the tx 2-3 ft from the rx.
Yes its called swamping.
As long as we are guessing have you made sure there is no UFO around somewhere? That make as much sense as some of the fixes mentioned here.
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