I have a 31% Aeroworks Extra that’s powered by fairly new a ZDZ 80 single / Falkon Ignition. I get one radio glitch / bump every 2-3 minutes or so. The interference will make one of the surfaces / channels twitch. Sometimes I can hear it in the throttle. Sometimes, it takes 5-7 minutes for the glitch to occur. It only occurs in the air and above idle. The problem has existed since I first began flying the new plane. The engine now has about 5-6 gallons through it.

I’ve changed the spark plug and used dielectric compound, changed the receiver, switched transmitters, on/off switches, and added an I4C servo isolator. I routed the antenna outside the plane and the problem seemed to get a bit better, but not much. There’s nothing loose on the plane. I’ve tapped around on the battery packs (2 nicad packs) and switches. The distance from the RX to the closest ignition component is about 11 inches. The choke and throttle servos are Hitec 5645’s and mounted inside the engine box. The choke and throttle pushrods are Sullivan nyrods with no metal-to-metal connections.

Ground range test is great. I can’t get the problem to occur on the ground, and it’s very intermittent in the air. We used a scanner at the field, and there wasn't anything else on my channel when this happens. Can an ignition unit cause something like this? I’ve been using an FM receiver. I read where using a PCM receiver might mask the glitch, and I do have one PCM receiver in the drawer at home. I sent one slightly twitchy HS5945 back to Hitec for them to look at, and I was quickly charged 20 bucks for a new replacement servo. All servos are fairly new. I’m to the point where all I can do is keep replacing components or try the PCM receiver. This is getting expensive and ridiculous. Any ideas from you guys? I’ll be glad to try your ideas, but my common - money sense is telling me to stop buying new parts and try the PCM receiver. I’ve been flying R/C for 24 years, this is my 5th gasser, and I fly mostly glow.
Getting disgusted,

JW

Hey John,i know of basicaly only 2 things that could cause the problem you described. 1 is that the plug u are using isent a resistor plug such as the Champion RCJ8. People will tell you that all plugs are resistor plugs now a days,but they aren't! The second thing that could cause ur problem is a bad or weekly insulated ignition kill switch. The kill switch woent show any signs of trouble on the ground,but once the plane is airborne and forward progress is achieved. The ignition system forms magnetic loops that the plane is passing through,these loops will affect the switch and cause radio interference. I had the same trouble with a sach's 4.2 about 3 years ago. Pulled my hair changining everything till i changed my kill switch,then no more troubles.

Hope this info helps you out,good luck.

Art

Hey Art You DA man!

Hi Art, the plug I'm using is an NGK BMR6F, which is supposedly a resistor plug. The previous plug was the same model number. I'll look into the ignition switch. When you indicated it could be a poorly insulated switch, do you mean something internal about the switch or the way it might be installed?

Thanks,

JW

John, I had a problem with a Goldberg Sukhoi ( not a gasser) that was a pain in the ***** to figure out. After trying just about everything including a PCM reciever I finally realized that the hub on my tail wheel was metal and I had also used a metal washer for a spacer on my main gear. After replacing the tail wheel and switching to a plastic washer my problems went away. The PCM receiver helped to lessen the interference but it still happened occasionally. Don't know why some of these companys use a metal hub without some kind of non-metalic bushing.

John, I know i'll get flamed for this, but definitely go PCM. I resisted it in spite of problems, but on a landing approach, a glitch can be a crash.

A loss of control for a second should not be masked with a PCM receiver, but a few milliseconds control loss is no big deal.

On another note, nothing interferes more than ignition EMI. I found the spark plug clip inside the boot was a teeny bit lose. The rattling around, ever so slight, of that connection gave me an intermittant glitch just like you describe. Squeeze that baby down till it is really hard to get on and off.

I talked to the Radio South people about my problem before I went to PCM. I was advised to go PCM. They called FM russian roulette.

When I told them I knew scads of people besides me flying FM without problems. They said they knew plenty of people who played russian roulette successfully for a long period of time, before they blew their heads off.

I have now acquired enough PCM receivers for all my gassers, and each time a buy a reciever, gas or glow use, I go ahead iwth PCM. Yes, it costs twice as much, but receivers last forever.

As for masking problems, here's what I do. When I range check, I set the idle down switch for low idle. Then I set the throttle stick up a couple of clicks so that the difference in RPM and sound are significant. If I glitch on range check the engine throttles back, because I have the fail safe set for low idle. This is working for me, something to think about for you.

Hope this helps,

The thing to look for for interference is not the receiver location as much as the closest any component connected to the receiver is to the ignition. Servos in the motor box is asking for trouble. I know that lots of people get away with it, but I've also seen lots that didn't.

I put servos in the motor box, but I optically isolate them by at least 12 inches from the ignition. One day I wondered just how necessary that was. After all, I was using a PCM receiver, the DA ignition is very well shielded, and my receiver was nearly three feet from the ignition. So I removed the isolators and connected the servos directly to the receiver. My ground range check went from 300' to about 100'. That was all the proof of interference I needed.

I agree with going PCM. For 10 years I flew half of my planes on PCM and half of them on FM. I've never had an FM receiver that didn't glitch at least rarely. I've never had a PCM receiver for which I've had any kind of a glitch at all. I figured 10 years was enough testing, and now everything I fly is PCM.

I'm going to try flying it with the ignition switch out of the loop and the ign. batt. hooked directly to the ignition. Wind was 20-30 today, so I couldn't fly. My throttle servo is routed to the isolator, not the receiver. I found the choke butterfly was kinda loose and rattling. I set things so it wouldn't to that anymore.

I get a kick out of the PCM / gasser guys that say in my situation, "don't try PCM". Ask them if they ever took their PCM receiver out of their gasser, and put an FM receiver in to see if there's RF noise in their planes, and usually you get, "all I fly is PCM."

Thanks for the input and I'll keep you posted when the wind dies down.

JW

John it could be as simple as a bad servo also.

I've had interference problems several times and troubleshot them to two bad futaba receivers(they were both new too!), a bad throttle servo, and a chaffing ignition pick-up wire.
Engine vibration sure causes its own share of problems.

Thanks
John

I have a similar problem with a ZDZ 80. I changed everything - receiver, battery pack. switches everything. I removed the spark plug and turned over the engine with the starter. With the spark plug out in the open and sparking away there was no interference with the receiver.
I installed a PCM receiver and am not comfortable with that solution even though I now have twice the range with the engine running than than I had with an FM receiver with the engine not running. There is still something there that is causing radio interference. PCM gets around it but it still should be fixed.
I am wondering if there is something in the Falcon ignition that causes interference under vibration and does not when there is no vibration.
I have a C&H ignition and will try that if I can figure out how to hook up the spark plug lead.

Dont' know what kind of isolators you're using, but unless they provide a large physical separation of wires they don't do much good. E.G. chokes and "optical isolators" that are in a little box don't help much.

Unless your isolator provides you with 12" of separation with no copper, it's not doing as much good can be done.

Here's a link to the I4C Isolator: http://www.i4cproducts.com/the_isolator.htm

It may eventually turn out to be the servos, but I'm still in the elimination phase with other components. What do you do with 9 basically new 90 dollar servos? If I send them in to be checked, they get replaced with new ones for an additional 20 bucks each ($180.00??), and I won't even know if the old ones were defective. That's not what I'm planning on doing. I'm simply not going to spend like a rich guy just to keep a 31% plane.

This FM receiver is the 3rd one in the plane. I don't think it's the problem.

Had to work today and couldn't get out to fly it.

JW

RFI is the level at which the ever present RF in the vicinity of an RF producing source causes a problem that is noticeable. The stray RF is always there. If a PCM receiver eliminates a noticeable glitch, that's good enough for me. I wouldn't want to fly with a predictable glitch masked by a PCM receiver. If it doesn't completely eliminate the problem with extensive range checking the problem is not really solved yet. On the other hand, an occasional minor glitch kept reliably out with PCM dosen't concern me. Of course you do all you can to isolate and eliminate the source, but it is not always possible.

Dirty Bird, I consider your RFI problem effectively solved, if you are not getting a glitch in the air. Engine-running range now double the engine-off range as you stated, is success. I don't blame you for continuing to experiment, maybe you'll get lucky. RF is very elusive and the interacting factors are probably in the thousands.

Technically, PCM radios are no more immune to RFI than FM radios. They are both FM but react to RFI differently. As I understand it a PCM receiver will not process a signal that doesn't fit within it's specifications, and waits until it gets a signal which fits the bill. Of course you have no control during this wait. If you can notice the slightest pause in control, your problem is definitely unsolved. An FM receiver will send the servos whatever it picks up without discrimination, and the results are chaos instead of delay.

Boy do I sympathize! Had the exact same problems on a couple of my first gassers.

Two different engines and ignition systems (BME & DA) and the same intermittant glitches that drove me nuts. Won't argue PPM vs PCM because that will not solve the problem. Check the simplest things first: On one airplane I had the ignition battery pack too near the alum. wing tube trying to set the CG - moved the pack two inches and success. On the other, the antenna was outside the fuselage, on the bottom, and the loose end would flap against the tailwheel bracket - moved it to the top and all glitches were gone.

These might sound obvious but my attention was diverted by all the advice from "experts" who looked 'em over and said I needed PCM, isolators, chokes, new servos, new receiver, twisted extensions, shielded extensions...yadayadaya.

OK, I flew it today and I know where the problem area is. I unplugged the ignition on/off switch and ran the ignition battery wire directly to the falkon ignition unit, and...no more glitches! I reconnected the switch and the glitches came back. Disconnected again and flew 2 tanks with NO problems

Now I need to figure out if the MPI switch is arcing inside or what the heck is going on. I wish I knew of a good quality switch to replace it with. Anyone know who makes a good switch for ignitions??

Thanks!

JW

Do you have an ignition cut off (i.e. RCATS or Smart-FLy, etc) ?

If so, you can rid yourself of the problematic on/off switch on ignition. I hard wire my cut-off switch to the battery and directly to the ignition . When the RX is off, so is the cut off so the battery is out of the circuit. I have a 2-leaded battery made up (fromeco) - one lead is a standard JR charge lead and one is a 18 gauge pigtail that is wired into the cut-off relay.

I have not used ignition switches for a long time. Also - cut-offs will soon be mandatory for IMAC.
DP

I don't have one of those. Hard wiring it like you did sounds like the thing to do.

JW

There is nothing wrong with the MPI switches for ignition or anything else there designed for. Was the switch new? If so you were unfortunate and got a bad one, every manufacturer has one or two come out bad. Bad solder joint, piece of trash (plastic shaving or solder) in the switch. If it was not new, well there are a lots of reasons and things that could make it go bad.

Glad you found your problem. We had a member pull his hair out with a small intermittent glitch and tracked it down to an inboard wheel collar being loose and turning on the axle.
Never know what can cause that little Glitch Monster to come out.

The switch was new. I use MPI products in other planes with no problems. For the purpose of putting this issue to rest, I'm hoping it is a bad switch. I think I'll try a different brand this time.

Thanks,

JW

i build all my own switchs for gas ignition,go get a locking toggle and wire it up your self using heavy duty servo leads and you will have a good setup for your ignition.i don't know what setup zdz uses for plugs but maybe a 3w switch will work

Pardon my ignorance, but what's a locking toggle? [sm=confused.gif]

Thanks,

JW