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Radio Frequency Interference

Old 02-16-2007, 02:50 PM
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Sailplane
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Default Radio Frequency Interference

Hi,

What means can be used to reduce radio frequency interference that may come from sources outside (i.e. radio towers, cellular towers, other people flying at parks close to your club field, etc.) or from within your own model (i.e. electric motor, ECS, BEC, Rubbing electrical wires, etc.)? I fly 72 mHz. Aside from twisting the wires, some pilots have told me to rap aluminum foil around the receiver and/or to pass servo wires through ferrite beads (thoroids.) If this true, where can I purchase ferrite beads?

Thanks,
Ernie Diaz
Sailplane
Old 02-16-2007, 03:24 PM
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BarracudaHockey
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Default RE: Radio Frequency Interference

Get a DX7 or you can minimize the risk with PCM
Old 02-16-2007, 05:31 PM
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Rodney
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Default RE: Radio Frequency Interference

There is almost no chance of getting interferance from cell towers and other radio towers. Someone on your channel is not solvable, you can not guard against it other than flying at a field that has good frequency control. Yes, you can be creating your own problem with poor installation such as metal to metal contacts that are not tight (any vibration can cause a problem there) or, with ignition engines, poor wiring or grounding practices can be a problem. The bit about wrapping the receiver in aluminum, twisting wires and toriod coils seldom will do anything to prevent the problem, in fact can cause additional problems, especially the toriod coils.
Old 02-16-2007, 07:38 PM
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Default RE: Radio Frequency Interference


ORIGINAL: Rodney

There is almost no chance of getting interferance from cell towers and other radio towers.

I disagree with this. I live within a short distance of a radio tower (or possibly a TV tower- not sure) and I can't fly because of interference. I lost 2 planes because I didn't believe that the tower was the cause. Both planes had brand new RX's in them with new crystals. I could fly them around a little but I guess at one point the interference signal was stronger than my TX signal.
I may be wrong, but I believe the tower is the culprit. I have found another place to fly and haven't had any problems. Now I have an abandoned airstrip on my farm
Old 02-16-2007, 08:32 PM
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Villa
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Default RE: Radio Frequency Interference

Hi sowega flyer

At the time that you were having your interferance problems, were you an experienced R/C pilot? At our field there are occasional comments about interferance. They seem to come from pilots that do not exibit full control of their planes.
Old 02-16-2007, 09:49 PM
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Default RE: Radio Frequency Interference

DX6. DX7 period. Watch yours cares and worries drift away.
Old 02-17-2007, 12:43 AM
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Default RE: Radio Frequency Interference


ORIGINAL: sowega flyer


ORIGINAL: Rodney

There is almost no chance of getting interferance from cell towers and other radio towers.

I disagree with this. I live within a short distance of a radio tower (or possibly a TV tower- not sure)
I may be wrong, but I believe the tower is the culprit.
If it is an FM broadcast tower, the signal stength may overpower the entire band your Rx is on with 1st or 2nd order harmonics. Your best bet is what others have said, ditch the FM altogether and go to 2.4 GHz (Spektrum DSM).
Old 02-17-2007, 09:04 AM
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Default RE: Radio Frequency Interference


ORIGINAL: Villa

Hi sowega flyer

At the time that you were having your interferance problems, were you an experienced R/C pilot? At our field there are occasional comments about interferance. They seem to come from pilots that do not exibit full control of their planes.

To answer your question, I have been flying for one year. I know- not a lot of experience, however, I do know the difference between being out of control and having no control. I take full responsibility for the planes I have crashed due to lack of experience, but in these two instances that was not the case. Like I said before I was reluctant to believe the tower had anything to do with it, so I ended up with two crashed airplanes instead of just one.
Old 02-17-2007, 11:38 AM
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Default RE: Radio Frequency Interference

A few comments, for what they're worth...

Placing aluminum foil around the receiver sounds like a bad idea, and I would recommend against it unless you are an expert radio guru. The ferrite beads are also a mixed blessing and I would recommend against them unless you are solving a known problem, such as ignition noise on a gas engine.

Transmitters and receivers do go bad. A guy at our field lost several planes because of an intermittant transmitter problem. He had previously sent the transmitter and receiver to Futaba for checkout and Futaba did not catch the problem. Eventually in desperation he bought a new transmitter and the problem went away.

If you the problem is really related to overloading the receiver from nearby cell towers then there is not much you can do. I have never seen this happen first hand but I guess it is possible. 2.4 GHz may be the answer.
Old 02-17-2007, 12:00 PM
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Default RE: Radio Frequency Interference

Thanks to all that replied to: Radio Frequency Interference.

Ernie Diaz
Sailplane
Old 02-17-2007, 12:23 PM
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Sailplane
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Default RE: Radio Frequency Interference

Villa,

You might be correct; I'm just trying to cover all the bases. One learns most when questions are asked!
Regarding experience, I've seen flyers with 15 to 25 years of experience shouting: I've been hit, I've been hit!!!! Pilot error or interference? Who knows?

Many thanks for your comments,

Ernie Diaz
Sailplane
Old 02-17-2007, 01:20 PM
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Default RE: Radio Frequency Interference

I almost lost a plane (it did go down and got some damage but was repairable) recently after losing control momentarily for what was obviously lack of radio control. It was obvious that all controls went hard over on a base landing leg. I tested the radio gear in my test bed plane and it performed flawless.

Recently, another experienced flyer suffered a similar snap with full controls and suffered almost the identical pancake landing getting wings level just as the plane grounded. He also found no problem.

We did share a common installation detail... we had both run the antenna wires through a tube parallel and fairly close to pull/pull wire rudder linkages. I recently completed repairs to my plane and ran the antenna outside the plane to the vertical stab and have flown it with no problems... he did the same and has suffered no more problems. We both however, flew the original configurations many time with no problems... and I can't say if the proximity of antenna and wire linkages is a real issue or not but I suspect that it might be.

Here is my thought... the wire control lines are in the ball park of the length of our 72 mhz antenna and therefore will be resonate at a frequency near our receivers. If there are strong signals near our receiver frequency... resonate with those wire lengths... it seems possible that these might inductively couple with our antenna and provide a signal strength momentarily greater than the tuned circuit of our receiver's ability to reject over the desired receive signal.

I'd be interesting to hear if any one else suspects wire linkage and antenna proximity as a possible issue? Until someone tells me it simply can't be so... I'm not running any more antenna parallel and close to wire linkages.
Old 02-17-2007, 01:57 PM
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Default RE: Radio Frequency Interference

Hi!
Get a good radio(JR or Futaba) and you´ll have no problem!
Old 02-18-2007, 08:14 AM
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BillyGoat
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Default RE: Radio Frequency Interference

In my opinion one of the best guards against interference is to have your system checked over and tuned by a certified repair tech. The reasons are obvious if your Tx and Rx’s are a few years old but I have new systems checked as well. When manufactures build a system it is tuned, unfortunately with a different module or crystal than the one shipped.

Having a tech tune your system to the module that is installed will guarantee that it is operating at it optimum. I was having a brand new out of the box Tx tuned and the tech said it was barely within an acceptable range. I sat and watched the scope while he adjusted a few things, looked like a drastic change to me. Haven’t taken a Tx in yet that didn’t need at least a little tweaking.

Modelers flying gas or glow planes spend at least a few moments setting the needle valve to get maximum performance out of the engine. Why not do the same thing to the most important element in R/C?

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