Mach1Latus

My Feedback: (3)

I'm Looking to put a light weight 100 twin in my 36% Katana. To balance it out I expect to put the throttle and choke servos on the motor box along with my receiver batteries. I have been told that modern grounded ignitions with bosch type caps and resistor plugs SHOULD not produce RF interference. I have witnessed a ZDZ 80 (single) and a DA 150 both experience RF interference problems.

My question is if I do have Interference problems what can I do to eliminate it, I would like to keep everything up on the motor box excluding the receiver?

Are the servo leads more likely to transmit noise to the receiver than the battery leads?

Will a power isolator like the i4C product block the noise?

Do those rare earth magnets work?

Thanks

Stephen

RTK

My Feedback: (1)

You should have no problems, I do it all the time. I use CF rod and ball links, keep everything tight.
I prefer this to nyrod because I "feel" it has less play and a more solid feel to it. This is just me, other will disagree.

I have never used any isolator, magnets,busses etc. and as of yet not had a problem. (knock on wood)

forgot the rx, I keep mine 8 + inches away for engine/ignition, 12 OR more if possible.

Mach1Latus

My Feedback: (3)

I know the ZDZ 80 was setup with gold ny-rods on the throttle and choke, so there was no metal to metal connection, but it did have RF noise. When the plane throttled up on the initial climb the plane was glitching all over the place. We throttled down and got control back.

Stephen

pe reivers

Every engine manufacturer recommends at least 8" distance from any ignition component, including battery, to any direct connected RC component. The modern all shielded ignitions are no exception. Also no wire or low electrical resistance pushrod that can pick up interference, and guide it to near the RC components, like pull cables or throttle control rods
This is not always possible, so either use chokes in your servo wiring, or tightly twist the servo wires. If you then with a paint stripper heat them up to the insulating sleeve melting point, the flat cables will melt together, and the twist will be permanent, thus forming a choke of some sort. This will prevent HF glitches from reaching the receiver.

Daryl Martel

My Feedback: (3)

I was experiencing interference on my CH Ignition converted G-62 powered Stinger a while back. I'd had the RX batteries and throttle servo too close to the engine. After moving them both further aft, approx 12 to 16" separation, the problem disapeared. I see in Model Airplane News on a few ocassions now where they've showed the throttle servos mounted up forward of the firewall. I cringe when I see a major magasine, or for that matter anyone here, condoning such a thing. While you may get away with it for a while, I suspect interference may crop up that'll bite you. Too me, it makes sense to try to maximise your RX reception ability (reduce potential for interference) by separating the engine gear and radio gear as much as possible. I also use a fibre optic kill switch - nice piece of kit!

Diablo-RCU

My Feedback: (1)

If you get radio interference when you throttle up your gasser, I would bet the problem is metal to metal vibration, and it doesn't have to be the throttle pushrod. It can be anywhere on the plane - like elevator pushrods using a metal clevis and no locknut. The radio pulse put out by the ignition has the same energy at idle as it does at full throttle - only the frequency will increase with rpm.

Tired Old Man

My Feedback: (1)

Stephen,

with all due respect to the others, I'd like to add some thoughts and experiences on the subject.

The worst offenders for actual RF are magneto equipped engines. The older versions being the worst by far. The reason for the italics will come later. Next in line for actual RF are ignition equipped engines that use 1/4" and 14mm plugs. Those are non-resistor type plgs, and breaks in the wire shielding can wreak havoc in a plane, regardless of component locations.

Best of the bunch are ignition equipped engines that use a resistor plug and Bosch shielded wire caps. If all the parts are in good working order, you can darn near stack the throttle servo, ignition battery, and the receiver on top of the ignition module and have no problems. I don't for a second suggest that, though.

Back to the italics. Far too many times I have seen someone pop up with an "ignition' problem that wasn't ignition at all. It later turned out to be a mechanical vibration problem. It has been a wire connector, a loose nut on a metal control rod (not to mention the one on the tx), a loose wire in a switch assembly, a bad solder joint on a battery, and many other things. The use of quality components that are carefully checked PRIOR to installation eliminates more "RF" problems that you can imagine. The re-use of older and previously crashed components have been a prime cause of "RF" noise. Gassers present vibration issues quite different from glow engines, and care has to be taken to prevent that vibration from having an impact on the components used.

There is no problem at all with using metal or carbon fiber rods for throttle linkage as long as you maintain some form of separation of the throttle rod to the carb lever. Usually the use of a simple ball link with a plastic housing or a nylon clevis is more than enough at both ends of the rod. Being certain that everything is tightly connected and the use of some form of thread locker on nuts and bolts to prevent things from coming loose helps a bunch.

With todays ignition systems, the condition, installation method, and quality of the components used have far more impact on "RF" than their location in relation to the engine.

RTK

My Feedback: (1)

Oh forgot to mention the receiver, mine is always 8" plus away from the engine/ignition.

and ditto the previous post.

JohnnyJ

My Feedback: (1)

I had a RFI problem with my G45 w/CH ignition in my Christen Eagle.
I installed a Bosch cap and had lots of separation between the ignition system and the airborne radio system.
I finally troubleshot it to a new futaba rx that had bad noise rejection. The second new futaba rx was the same.
I installed a Hitec Supreme and the problem went away.
It's been good ever since.

My next RFI problem was with my ZDZ40 equipped Texas Hurricane.
After much troubleshooting, I traced it to a bad throttle servo.
I installed a new servo and the problem went away.
I now have a free Futaba S3003 servo for anyone who will pay for postage!!!!

I will mount throttle servos fwd of the firewall if the engine has a fully shielded ignition system.
I am careful of the unshielded components.....switch harness, battery, and associated wiring as I believe that they emit some RFI.

Thanks
John

pe reivers

Silversurfer.

You may be right on many items in your post. This is common knowledge, and it does not harm to stress the importance of these causes for interference every once in a while.

Having said that, I find it unwise to even suggest the shortening of distance between ignition-bound components, and plane controlling components.
Whilst some makes of RC equipment may be less prone to Radio Interference than others, one may get away with using other brands for a period of time like another poster suggested. The receiver brand however was not subject of this topic. The subject is ignition generated RI in general, and safe practice to prevent it.
In this practice, I would stick to common known measures to prevent RI by ignition systems, without even differentiating between modern electronic ignitions and magnetos. A few main rules should be considered here, and from these rules, safe practice results.

Rule 1
every steep angled voltage transition is built up of many components, including radio frequency. These RF components, due to their nature, can be transmitted without the presence of any conductor.

rule 2
current conductors not only convey signals by direct current transfer, but also can act as aerials, to receive, or radiate Radio interference.

rule 3
Radiated (airborne) Interference's field strength deminishes rapidly with increasing distance, typically 6dB for each distance doubling. (6dB equals about 1/4)

So in order to eliminate, or avoid Radio Interference one should:
- Shield the interference source to the best ability (all rules), and ground the shield well.
- not use current conductors (metal pushrods or wires) leading from the interference source to the radio equipment. (rules 1) and 2) )
- provide maximum distance between interference source and Radio equipment (rule 3)
- prevent, that any RI radiated into servo or battery leads (rule 2) will reach the radio receiver by using chokes or twisted cables.

Mach1Latus

My Feedback: (3)

Thank you all for your feedback. The loose metal control rods were something I would not have thought of, I will keep that in mind. I do plan on keeping the receiver +12" away from the ignition system, and I will be using all new components for the build. I would like to push the heavier components, batteries and servos, as far forward as possible to help balance the plane.

A few people mentioned chokes, what are these? how effective are they in blocking RFI.

Thanks
Stephen

pe reivers

A choke is a coil. It has a high resistance to alternating current. The higher the frequency, the higher the resistance. Model shops sell servo extension leads with chokes in them. to improve properties, the coil is wound around a ferrite ring. Twisting the servo lead has a similar effect.

Tired Old Man

My Feedback: (1)

Also available from Cermark.com.

In reality, the location of the receicer is usually determined by the length of the servo leads. Where they all meet is where the receiver usually goes. 99 times out of a 100 it will be a good distance from the engine/ignition. Same holds true for ignition batteries and switches. The length of the wires is pretty much where they end up. It's almost a natural that they end up well separated.

Now, I'm not, nor have I ever professed to be, an engineer of any type, let alone electrical, so I don't try to over analyze designs or products. I just go with what always works. If I want to drive a nail, I hit the darn thing with a hammer. I don't attempt to determine how much kinetic energy and angular force is required in to set the nail.

If I was to seriously take a look at all the things that could go wrong with a radio controlled plane, I would like as not take up model railroading.

pe reivers

I totally agree,
Living in ignorance is easier.

Tri-stan

My Feedback: (1)

I have a question which really seems rather basic but has not been talked about very well. Does it really matter how far away your receivers and wireing are from the ignition if you have a secondary ignition failure such as a bad wire or imperfect connection of the end cap and plug? Since a lot of electromagnetic energy is caused by imperfections in the secondary ignition, I've always thought that distance does not matter when you have a secondary ignition problem. Interference is interference, no matter if your radio gear is 8 inches or 8 feet away from the interference source. I've seen installations where throttle servos are placed right next to the main ignition box, suxh as on one of the BME Aircraft Ultimates a friend of mine is building. Then the Composite-Arf models seem to encourage a very far forward location for the throttle servo as well, which is right against the back of the motor dome on their Super Extra. It just seems that if this was a really bad problem, the aircraft makers would not be recommending putting throttle servos there.

TM

Mach1Latus

My Feedback: (3)

Pat

I agree with you. Go with what works and be practical about the setup. I trust in my observations more than my analysis.

Stephen Latus, P.E.

pe reivers

See rule number tree in my previous post. Rephrasing that rule to omit dB: Signals are reduced in strength by the inverse cube of the distance. Meaning, that when a servo is 16"away, its radiation level is 1/16th of the servo placed at 4"distance radiation power level is:
(4/16)^2=0.0625 times. Quite a large reduction, giving the transmitter signal a fighting chance.

I do not know why some plane builders do not care where that nearest servo or receiver connected lead is.
I do know, that Engine and ignition manufacturers advocate as large a distance as is feasible.
From my own background and limited knowledge, I am very much biased to believe the ignition/engine manufacturers. There always will be exceptions to the rule, but that does not change best practice.

dirtybird

My Feedback: (5)

It just makes sense to keep your radio system as far as possible from the ignition system. However, I have to agree that if you have a brakedown of the shielding system you will not be safe if you are 8' away. That spark in your spark plug has as much RF energy as the transmitter and it is much closer than the trransmitter.

pe reivers

That is right.
In that case, the plane is too small. Good maintenance and protecting the shield will mostly prevent such a failure mode however.

I did have it on my first gas plane. In between being overruled, the receiver reacted sort of on my signals, and I was able to limp the plane in. That taught me once and for all how not to do it. A burnt child.....

ed42d-RCU

My Feedback: (13)

Just read through this thread and got me thinking about a cut in my wire on my BME 50 with CH ignition. I haven't been able to run the engine yet, so I'm not sure if there are any problems. I would like to know how I should fix this cut. Any suggestions? Thanks in advance.

Ed

min

Electric tape, lots of it.

Good luck

PaulBK

i would be very interested in knowing more about the ignition issues related to the DA 150. The DA ignitions are awfully quiet, and having been around them since their inception, i have never heard of anyone experiencing an RF problem with any DA engine - be it a 150, 100, or 50. not to say it isn't possible....just extremely unlikely.

i also seriously doubt that if you move the two servos back a bit it will have any real impact on your balance. the weight of a single (or two) servos is pretty insignificant in a 35% airplane. but the bottom line is that most of the pilots i know pay little or no attention to where things go - i have personally sat my ignition battery right next to my receiver and had three batteries within a couple of inches of the ignition module. i have friends that have throttle servos on motor boxes...no problems. a lot of so called "rules" are just rhetoric. the only "rule" that i personally subscribe to is the use of a PCM receiver in an ignition environment.

dirtybird

My Feedback: (5)

With a PCM receiver you don't even know if you have a problem.