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Radio Interference

Old 12-08-2003, 09:46 AM
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5 oclock charlie
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Default Radio Interference

What's the real deal with the Rx antenna passing by a servo. Does it (can it) cause radio interference in a glow engine setup? If so, how close is close.
I've gotten responses all over the map on this one. Help!
Old 12-08-2003, 11:37 AM
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michpittsman
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Default RE: Radio Interference

A current-carrying wire can cause interference if in close proximity to an antenna especially if laid parallel; crossing them at 90 degrees should negate this effect...JIM
Old 12-09-2003, 11:39 PM
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Live Wire
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Default RE: Radio Interference

Correct me if I am wronge, Electromagnetic injection or transformer effect.
Old 12-10-2003, 09:18 AM
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5 oclock charlie
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Default RE: Radio Interference

Hey Outlaw I think you've hit on something.

My question sort of ruled out the magnetic effect as I am interested in the effects of the antenna wire running by a servo not wound around it. Your thought of magnetic injection is closer to the point however this would come into play only if the routing of the wire produced some sort of coil in the antenna wire. Also "injection" in milivoltage systems may be too strong a term. "Rejection" may be closer to the point in this case.

I suppose what I'm really asking is "What is the electromagnetic effect on the antenna to recieve signals imposed by a current in parallel wires in close proximity to each other and how does this effect on the antenna vary as the distance between the two increases or decreases?"

I'd welcome your thoughts as you seem to have much experience in this area.
Old 12-10-2003, 09:47 AM
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Kaos Rulz
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Default RE: Radio Interference

I belive what you're refering to is "Inductive Reactance". This is where a small current can be transfered from a wire actively conducting, to another wire that is in close proximity. This transfere is most likely to happen if both wires are running close to each other in parallel. In the world of RC, this usually doesn't happen, however, it is still a good practice to route the antenna as far away from the battery and leads (most likely culprit), on/off switch (second most likely), servo and leads (least likely). If the antenna wire must cross another wire, cross at a 90 degree as michpittsman stated. I've seen more interference generated from metal on metal, than for misrouted antennas.
Old 12-10-2003, 04:19 PM
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onewasp
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Default RE: Radio Interference

The antenna wire is the cause of Inductive Coupling. Think of it this way; when an electric current is turned on and off and on etc. (A/C) a magnetic field is created (at 50/72/75mhz there is a whole lot of "on and off" going on. If too close to servo wires (within the created magnetic field), then an Inductive Coupling has been made and the results aren't real pretty on R/C craft.

Generally, the disturbance created can be picked up in a range check or if airborne you'll have less than precise control ----usually enough to get the plane down----.

It is real and it can happen. The reliability and tightness of today's radios has created many sloppy, self defeating, practices to get by, which in earlier days would have made the radio useless. I could list a few but the cry from the younger set would be -----"I do that all the time and have no problem" You ARE degrading radio performance through these actions you simply have enough performance enhancements now that generally you "get by". Sooner or later it will bite, so the best insurance is to go by the book.

The above is an oversimplification but the principles are correct.
Old 12-10-2003, 06:00 PM
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Live Wire
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Default RE: Radio Interference

Must have been thinking about the doctor!! It is inductive ,not injection. rapping wires in a coil , running side by side can have a reaction. Motors run on on the building up and breaking down of magnetic poles! so the further away from the part you can run wires the better. There is also capacitve discharge and reaction,which is way to complicated to discuss here.
Old 12-18-2003, 08:13 AM
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5 oclock charlie
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Default RE: Radio Interference

Thanks for your input fellas. It's given my some to think about.

And, Outlaw, get some sleep my friend. Doctors can't help.
Old 12-20-2003, 04:01 AM
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3DFanatic
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Default RE: Radio Interference

I've never had a problem running my antenna by servos (my 25% Suk26 features teh antenna running right through the middle of a cluster of 3 digitals) but when I put the reciever next to my rudder servo in my Laser3D, I almost lost it due to horrible glitching. I've since moved it about 3 inches away and have had no further problems.

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