I have a very strange problem with a Spectrum receiver and a fuji 64 EI.
I seem to be getting noise when I start and run the engine.
I have isolated the throttle servo with 4in of nyrod the EI module is mounted on the engine block I have about 6.5 in. between the throttle servo and EI unit.
I have swapped out the EI with the same results.
I have the EI battery close to the receiver
Will moving the battery and and switch away from the receiver help?
None of my other planes have done this.
Also I have swapped out the receivers.

If you have the ignition battery near the receiver battery then you have the wires from both too near each other also. Just because it works in one situation does not make it right. Follow your radio manufacturer’s guidelines for the best performance. If you have one of the early Spectrums then this is particularly true. Here is a quote from the Futaba website. Dan.



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).

All the old 12" stuff coming from the early days of gas engines is pretty much not valid with 2.4GHz radios and things like the throttle servo and ignition battery being 12" away didn't even apply to a clean 72MHz setup. Throttle control rod isolation is still practiced but not much of anything else.

That said; the primary cause of ignition noise issues with 2.4GHz radios is loose ignition sparks, there isn't a radio system out there that can put up with 20,000 or so loose volts getting discharged in close proximity. That can come from say a system that requires a resistor sparkplug that the user has replaced with a non-resistor sparkplug. Loose connection between the sparkplug wire/cap and the sparkplug. Cracked ceramic on the sparkplug can also produce issues.

If you've already tried a different ignition module one would suspect that a loose connection between the cap and plug is probably not the issue, check for the others I noted.

Do you think I will have to move my battery and switch?
I am changing the EI module to one that has a shielded spark cable.

There's your radio interference source, especially if also using a non-resistor plug cable wire and spark plug. In a setup like that, the battery leads too carry full radio interference spectra, so the battery must have maximum separation from all radio gear.

v meek, Always follow your radio manufacturers’ advice. They understand best about what will make their equipment perform as advertised. Send them an email and ask them if comingling the receiver and ignition batteries and wires is acceptable. Dan.

I respect your opinion greatly, however I must make a point about modern radio/ignition component separation. I've posted pictures on this forum of my 40 size GP Super Sportster with it's converted SuperTigre 51 detailing the radio/ignition installation. The ignition used has been both the CH and an RCexl with equal results. The ignition box literally rests against the receiver, with a thin layer of foam between, which is a Spektrum AR7000. Both switches are within two inches of each other and the battery packs lay one on top of the other. The throttle control is by metal flex cable. This configuration has been flying for almost 4 years without a single glitch which I can now verify through telemetry while flying with my DX8. Never a single "hold" which is the same as saying a glitch. The frame loss has never exceeded 3 in a single flight and Spektrum says up to 20 is OK in a flight before needing to check things out.

I have little choice but to use this setup as putting an ignition system in a 40 size plane is a nightmare to say the least. I had to pretty much shoehorn it all in and getting anywhere close to a 10" separation much less 12 would have been physically impossible. Heck, just getting it all in was nothing short of a miracle. It sure is a fun little plane though as it easily exceeds 90 mph and gets close to 100 on a perfect day. 16 oz of gas lasts all day so it's cheap to operate.

I agree with the ignition lead needing to be shielded. Sometimes even if using a resister plug. The only time I have ever had ignition interference was using a Zenoah G26 with mag ign. After making my own plug wire shield, grounded at both ends, all interference went away. The plug used was the original type with resister but it still caused interference until the shield was added. My radio at that time was a 72mHz.

Jezmo. look at post number 4! The OP is using an unshielded ignition! Both CH and RCexl are very well shielded.

Fuji's with the unshielded cable were notorious for being noisy. We sold a lot of Bosch caps to Fuji owners. Now with Bosch being unavailable the best thing is a shielded ignition, next best would be a RCexl cap on the Fuji ignition.
Please note that the Fuji ignition is weak and that adding a resistor RCXL cap and shielding may reduce the spark to the point where it wont run

+1 to what Zeeb and Jezmo said.

12" is old school when talking about a modern and correct setup.

If you have no damage to the shielding that statement is true.
IF, IF

I have an XYZ ignition module. Since i read it is noisy I decided to test it. I put the CM-6 plug in it and connected the sensor lead to a function generator. With the function generator I can drive the spark at a speed up to the point where it stops working.
I sat an XPS 2.4 receiver next to the spark plug and turned it on connected to my transmitter via RF.
No matter what speed I drove that spark I could not get it to interfere with that receiver. The receiver was never more than 6 inches from the unshielded spark plug.
I am going to make a video and put it on Utube.

RFI RULE 1 Always do the most you can to prevent, NOT the least that will let you fly.

+1, though I am guilty at times.

The only thing that has really changed is the quality of the newer generation ignition units. Those of us that were running ignition 15 and 20 years ago had to go through lots of things to prevent interference. Please do not think that the 2.4 equipment is a fix all to the " Old school " rules. One would be foolish to install radio equipment close to ignition and ignition power sources. Even the IBEC units have filtering designed in to make sure noise dosen't get back to the RX. IMO unless one is very familliar with RF and antenna function he should not suggest against techniques that have been proven for the past decade.

How about 20 years working on radios, avionics, onboard computers, weapons systems, and radar systems on naval aircraft and teaching network cabling and troubleshooting at a major university?

I suppose I am at a loss as to how you can suggest placing a receiver or it's power source next to a high voltage discharge device. BTW the company I work for manufactures some of the equipment you have experience with. Not wanting to get in any type of contest here, lets just say we have a difference of opinion.

Do you know how to spell H.E.R.O. ?

2.4 ghz is in fact a fix all to all those old school rules. I read somewhere that systems operating above 300mhz are immune to RFI generated by ignition systems. I have not been able to verify that so I have been running tests to try to verify it. So far everything I have done indicated it is true.
Unfortunately 2.4 has other idiosyncrasies. One, everyone should know about by now. That is it contains microprocessors that are intolerant of low voltage.
Another is it is very susceptible to multipath.If you remember the TV with rabbit ears antenna,an airplane flying over would make the picture flicker.The signal that bounced off the airplane arrives at the TV with a different phase as it traveled longer. It subtracts from the main signal and causes a flicker.
The frequency diversity (Hopping)systems are less susceptible to this problem.

OK so let me see if i understand what you are saying here. 2.4 can have issues with signal reflection but if you have an ignition module with a bad ground leaking 10,000 volts the 2.4 RX dosen't care? According to this and what others are claiming, the OP's issue is immaginary.

The OP says he seems to getting noise. He apparently does not know what he has.
What do you mean by ground leaking 10000 volts? Its not like water pouring out of a hole.

The way I read the first post my understanding is that his radio seems to be working fine until he starts the engine. So i would take that as the ignition is affecting the RX. Leak is a fairly common term in the RF industry. If one was able to see radio waves, pouring out of a hole would not be that far off.


Rather then argue this to death like what usually happens here on RCU, lets see what the OP decides to try and what improvements he makes. My suggestion would be to seperate his ignition and ignition power from the rest of his electronics, this is a tried and true method of reducing ignition noise getting to the RX

Its interesting that in my 50+ years working in the RF field I never heard of an RF leak. I guess I will have to add that to my vocabulary.
The OP does not define what he is seeing. We don't even know what he is getting but several have jumped in and repeated the old school fixes none of which works.
There is another problem caused by a running engine. Its called vibration. It could be causing what he is seeing. But then we don't know what he is seeing so maybe we should not guess about that either.
Another problem with a running engine is the sound pressure it generates
When trying to fix a problem we should first identify what the problem is.

duplicate post

Just to throw my 2 cents in here - I used to fly my first gasser with an electronic kill switch installed. Radio and ignition curcuits were separated, the only interface was the kill switch. I had bad interferences when I was flying. On the ground everyting was working fine.
After relocating the batterys and moving the ignition away from everything else, I still got the problem.
That happened until I removed the kill switch, everything worked find, no jitters.
And this was on A 2.4 GHz radio, never had any problems with this before and after this incident.