It was originally used to minimize the effects of gas engine ignition on the servos. It was widely used, and it didn't "do nothing." It often worked. It was also used to minimize outside effects, and for that it didn't "do nothing." It often worked for that as well.

And just about as often on both, it didn't.

Now, with the 2.4GhZ, RF noise problems have become relegated to being obscure, even rare problems. It takes something pretty "Messy" RF noise-wise to get past it. But in this world of a bajillion (technical term) electronic signals (many, MANY of them being 2.4 GhZ - even our remote home phones are now 2.4GhZ), there are enough to find their way in upon occasion.

~ Jim ~[8D]

Bingo!

Well it makes your runs longer as well.

I had the exact problem with an FPE 2.4. I'm sure it's not what you want to hear but I sent the ignition to C&H and had them replace the plug wire with a metal cap. Problem solved.

I have had the same problem, JBA 15 cc with Rcexl ignition and Rexl optical kill switch.
After disconnecting the kill switch the interference went away.

The shielded wires and the metal caps seem to make a huge difference.

~ Jim ~

Having just had a similar problem with a gas engine and read what the OP has said it looks to me like the problem is he does not have a shielded HT lead or cap. I would suggest he replaces his ignition module with one that has a shielded lead and cap preferably one designed for an NGK plug. I replaced the cap on mine after having terrible problems getting the engine started and then to have the elevators go to full up when the engine did run, I fitted the new cap and soldered the braided sheath to the cap to make sure the earth path was complete. I found that tip on Just Engines site under replacing the 1/4 sparkplug caps. Hope this helps, by recently I mean first start Sunday replacement cap fitted Tuesday and flown yesterday.
Jim.
BTW I fly on 35mhz and after the cap change no interference at all.

Myself and another had the same problem using the HS 645mg servos.  We replaced them with HS 5625mg digital servos and it solved the problem.

Interesting. I just decided NOT to use two HS645MG servos, because I'm fond of JR servos, and I had enough JR ST126MG servos to go around this project. I'm glad I did.

~ Jim ~[8D]

OK I want to thank all for there help. I just now pulled the RCxel Opto kill switch out of the circuit and the problem went away. I don't understand why but it works. Can anyone explain why the opto kill would cause interference? Well at any rate that was the problem so I will probably just do without till I can upgrade the ignition to the RCxel ignition and then I will try the opto kill switch again.

Thanks to all who responded I knew that I would get all the help I needed here on RCU.

I Love this Hobby not only because it is great fun but because there is always someone willing to help someone who is having trouble or who is new to the hobby.

KEEP UP THE GOOD WORK GUY'S YOU'RE THE BEST!

Great to hear!

Another problem bites the dust. Something else to remember to solve this problem in the future.

You never get too old to learn something new.

~ Jim ~

Suburban, there’s a good reason that optical kill switch caused the problem. Take a look at it. One set of wires goes to the ignition battery. Another set goes to the ignition module. Those two sets of wires could be contaminated with radio frequency components that are in the 2.4 Gigahertz range or some other range. Those wires are very long and can act like a perfect antenna transmitting the RF just like the antenna on your transmitter. The third set of wires goes right in to your receiver. They would conduct any contamination in to your receiver. You have two things going against you, radiation and conduction. The Smart-Fly kill switch has a transmitter and receiver that are separated by a lengthy optic fiber line. This will give you the isolation all the radio manufacturers recommend. Always make sure that all your ignition components and radio components are separated from each other as far as possible and I mean always. Thanks for posting the solution. It’s a good thing you found it. By the way, there is nothing wrong with the carburetor cut off. It was satisfactory for years and still is. Dan.

I'll give my IBEC a try first. It'll kill the engines in a variety of ways, under a variety of conditions. Without a switch, if the radio reception fails.

I can always kill the engine some other way. From what I see out there, for all the IBECs out there, very few have any issues.

This is my first IBEC. I'm going to give it a chance.

~ Jim ~[8D]

Dan,

After your lengthy objections to these IBECS, I'm going WAY out on a limb here, without actually asking anybody first (that wouldn't be fair.), but you wouldn't by any chance have anything to do with, say, the actual MANUFACTURING or SALES of the Smart-Fly, would you?

Reading your post, I just couldn't resist asking this. If I'm off-base, I apologize.

~ Jim ~[8D]

Suburban,

Before you spend any real money, ask one of your flying buddies if you can plug in HIS Opto-kill and try to run it, and see what happens. If it replicates the problem, borrow an ignition and try that instead. If it stops, reinstall your Opto and you probably will still have good results (this would mean it was the ignition and not the Opto).

Identify the bad part this way.

If an electronic component goes bad in a certain way, it can send a sort of noise through the ground wire to the system. It doesn't happen often, and switching out the part solves it. The problem may not be your Opto-kill switch, it may be your ignition. Whichever it is, once you identify it and switch out the offending item, you probably won't have any issues like that again. It can happen from an opto-switch, a servo, anything with a PC board.

I hope this helps some.

~ Jim ~[8D]

Good question Jim. The answer is no. I've been in RC since 1952 and it was the reason I became an electrical engineer. My father spent a fortune on me so I could accumulate all my degrees. Luckily I speciallized in radio frequency engineering including the microwave region. I don't claim to know what I am talking about but I may be ahead of the doctor, lawyer, plumber or someone else that did not get his brain shrunk trying to memorize all that stuff for six plus years. Notice, I said "stuff" instead of something else because all I wanted to do was past the tests at that time. I probably forgot more than I learned by now but I can help the guys in this great hobby of ours a tad more than someone else. Experience does count but it's a tough way to learn. You never want to defy the laws of physics because you will never get away with it in the long run. And that usually happens when we are flying. Suburban is lucky. He found his problem before he got off the ground. Dan.

Why do I get the feeling I wasn't actually answered?

Lol

~ Jim ~[8D]

If you are an electrical engineer you should spend some time on the way a spread spectrum system system works. Then you will realize your explanation is impossible.
Then spend a little time on why a resistor in the spark plug stops RF interference then you will realize there cannot be any RF generated in the 2.4GHZ domain by the spark plug.
Even better get a good spectrum analyzer and you will see for yourself.
BTW I am also an EE with many years of RF experience.

OK. If you don't agree with me, you can at least listen to the RC manufacturers. Maybe they know what they are talking about. Here is Futaba's advice:
Guidelines for setting up gasoline engine models.
All ignition equipment, including an electronic kill switch, must be mounted at least 12", and preferably 14", away from all radio equipment, including throttle servos, etc. Ignition kill switch should always be on opposite side of fuselage from radio kill switch. All pushrods going to anything related to the engine must be non-conductive (just nonmetal clevises is not sufficient).

I'll attach a couple of emails I got from JR and Hitec. Dan.

I know what dirtybird is saying, and I agree with him.

Aside from what he said, it's plain that everything is not so black and white as you say, Dan. There are a hundred shades of gray in there, what with all the different radio brands, different types of batteries, servos, receivers, voltage regulators, Opto-kill switches, Opto-Kill switches WITH voltage regulators and adjustable voltages; and I'm sure I forgot plenty of other items.

There's more than one way for an electronic item to fail, and before you go into another soliloquy about your background, I should probably point out that there are many others in RCU with backgrounds in digital proportional electronic controls. Planes aren't the only things controlled by them, and aren't the only things affected adversely at times.

Most of the items you just mentioned aren't being contested, and they're mostly gas engine installation 101 items, and have been for many years, and most of them were developed for 72MhZ, including the spark plug reference. Though admittedly, I still look at the plug first if there's an issue, more out of a knee-jerk reaction than conscious troubleshooting policy.

And there's always something new to learn.

~ Jim ~[8D]

So why did the OPhave this problem in the first place? According to this nothing form the ignition should have gotten in but it did. Theory is all fine and good and I wish I could tell you where my practical experience came from but I simply can't. Let's just say it's DOD related and move on. Time and time again I have worked on prototypes that in theory should work just fine. Rarely is that the case, things usually hit the targeted specification on the third try or so. Unexpected things happen. If the ignition is spilling enough power it can effect any frequency maybe not directly but it can affect the <span class="st">paripherials </span>such as a cut off switch. IMO removing the cut off simply took the component out that was being affected. It did not remove the unwanted RF. Sheilded plug caps and wires is still my reccomendation. Being that the RCXL units are so inexpensive that is the route I would go.

It should be a clue that it was not an RF problem because the other servos were not affected.
I can't say why the kill switch caused the problem. There is not enough information there to analyze it.
My guess is there was a coupling thru the power supply. There is some problem with the kill sw. that overloaded the power source. But I don't know. I have no information on the kill sw.
Keep in mind when you write to the manufacturer you usually don't get an answer from the technical people. Some tech writer usually answers your letter.
If you would like to know how SS works and why a resister in the spark plug stops RF PM me and I will write an explanation. I have been out of school to long to explain it mathematically so I have just tell my impression so it wont be hard to understand.

Part of the problem was those were written when 8 tracks were in vouge. The kill switch may or may not have been the problem, I agree that further testing is warranted. I use the RCExcel's in all of my gas planes, they work just fine w/o interference, though like recievers and servos, anything can go bad or be bad out of the box; it happens.

The RCEXL opto kill switch created a problem for me until it was removed.
On 12/2/2011 I posted my problem with the RCEXL opto kill switch in Post #139 on page 6 in the "Has anyone tried the new PTE36R ?" thread http://www.rcuniverse.com/forum/m_10..._6/key_/tm.htm
Preceding that post there were a number of posts in which people were trying to help.

Post #142 and Post #150 followed my post and may be of some interest.

Barracuda, I sent you a PM about a different subject. Dan.

Did you use a non-conductive throttle linkage? A conductive throttle linkagehas beenknown to"feed" ignition noise into the throttle servo and back to the receiver. Also, if you are using ganged Aileron servos (i.e. two on each wing): On my 33% Extra 300L, I separated the ganged aileron servos using smartfly's Equalizer II. Theyacted erratically w/o the Equalizer in between the AR9210 receiver and the servos. I could not just use Ys on ganged digital servos.</p>