Hello, I installed a larger engine on my Wildhare extra and I'm going to place the battery pack for radio power in the tail for weight in the back to get proper cg. My question is, can I put the ignition battery in the back, but on the other side of the fuse away from the radio pack. It will be about 3 inches from the radio pack. The power wire from the ignition pack will pass about 1 inch from a servo as it's routed to the front. Only the battery will be back there, not the ignition module. Does the power wire to the ignition pack cause interference too? Doesn't seem like it would due to it being direct current dc rather than alternating current ac, and it is not the actual module and the plug wire that causes the interference, so what y'all think? If can put the ignition pack in the back, that will be a lot less parasitic weight added to proper cg the plane. Maybe wrap the power wire with something, any help please, thanks Randy

What Radio do you use 72mHz or 2.4gHz; I have been told that with 2.4gHz, battery placement is not as much of a problem as it was with 72mHz, hopefully others can offer other info as well.

According to Futaba and all the other R/C manufacturers keep all the ignition components as far away from the R/C parts as you can. Anything less puts your plane at risk. Dan.
http://www.futaba-rc.com/faq/faq-gas.html

They can be right next to each other, no problem, despite the antiquated advice you're likely to get from some on these forums on this issue.

Agreed, just like how Futaba use to recommend that we do not use lipos in our Transmitters.

Karol.

I use futaba 2.4 8fgh

It's not going to be a lot of extra effort to put them on opposite sides of the fuse (if you want to be super careful), not needed IMO though.
Don't forget to use heavy ext leads though, as you will get voltage drop.

groran, like Mr. Moderator says “Who are you going to listen to? The manufacturer of your R/C equipment or some one on RCU?�. Here are two emails I got from JR and Hitec. They both concur with Futaba’s recommendation. Don’t comingle the ignition and R/C equipment. Keep them separate. Well, who are you going to listen to? Mr Moderator or someone at Futaba? Dan.

I'd listen to Mr. Moderator; these manufacturers stay on the side of caution, Futaba tells us don't use Lipos in their Radios, yet hundreds of people do and never have a had problem, Futaba once said that there was nothing wrong with their 14 Channel 2.4 receivers, yet it was shown that they shut down when exposed to normal operating heat found in fuselages, and if there wasn't anything wrong with these receivers, then why did they start making them different, anyways, ask around and see what others have done.

Wikipedia says this The electric charge flows in a constant direction, distinguishing it from alternating current (AC). Well, if it flows in one direction from the battery, how can any other components be affected? The power is flowing from the battery to the ignition module, not back to it. So it's my understanding that the radio system will never see any interference this way. Now if the ignition module or spark wire was near, then yes, I can understand. Am I wrong on the theory of the dc voltage coming from the ignition battery? I'm not saying anyone is wrong, just reasoning on the matter, thanks Randy

Let me start off by stating two things here, well maybe three LOL . I have adressed this topic before and have disagreed with some there who have already responded. I currently am employed by a company that makes antennas for military aircraft. I have disussed this very thing with members of our engineering staff.. That being said this is the way I see this.

1. Running power leads longer then 12" is a bad idea to begin with. The power losses over 12" at the current our airplanes can draw is higher then we think, especially when using 20-22 gauge wire. I can't really throw a number up here because there are just too many variables.

2. By doing this I am going to assume the worse ( because it is the safest thing to do ) I am going to think that you are just connecting flat extensions together. Each connection is a power loss. Now the kicker, the extension still has a signal wire that is unused but does plug directly into the RX. Depending on signal strength, it CAN act as an antenna and transmit the noise directly into the RX. Un-twisted DC power wires can emit an EMF field that gets stronger the more power that flows through said wire.

3. Your rudder and elevator leads are most likely being thrown into the mix as well. Their long leads can pick up on noise. If you have pull pull for the rudder, steel cables and pick up on noise.

4. There are alot of guys who say the " Old School " install of seperating ignition components will claim to have not had any issues by just throwing their stuff in the airplane and I am sure they are being truthful. Last time I had a radio issue was 2006. About the same time I started learning more about how our systems work and what I should be doing differently. IMO that puts us on even ground as far as a track record goes. I like to err on the safe side and advise " Textbook" Installs. I wonder if anyone advising to just thorw the stuff in and don't wory about it would be willing to write out a check should you have an issue and loss of your airplane?

Randy, you’re doing the right thing by trying to figure this out while being bombarded by all of this excess rhetoric. My father spent a fortune paying to make me an electrical engineer. Unfortunately, I have forgotten more than I had learned. But here goes.
Your engine generates a spark around 100 times a second. Each one of those has the potential of containing radio frequency components that fall within the band that your radio is operating in. They radiate around the ignition system as an electromagnetic field and are conducted within all its wires going to and from its batteries and spark plug. By bringing the receiver and ignition components close together you violate all the advice from the radio manufacturer to isolate the radio components from the ignition system by eight to 12 inches or as much as possible. It is possible to pick up this RF through conduction and radiation. A lot of the guys ignore that by doing what is convenient or less expensive and get away with it. This gives them a sense of security that is very false. This is good because I hate to see guys go in but all you need is a few seconds of sparks that are on your frequency and you will lose control.

Randy, not an EE and no expert. But in my Top Flite 60 size Mustang I had to mount one battery all the way back in the tail, behind the tail wheel (ign.) and the other just behind the wing saddle (radio). I tried to keep the wires to the ignition battery as far away from the radio as possible but in that narrow fuslage, still close. Ing. modual is up front just behind firewall. Radio is towards the rear of wing. Using Futaba 2.4. 220 flights on the plane and no problems so far.

Its too bad your dad had to spend all that money. I got my education paid for by my uncle - uncle Sam that is.
But you don't need an engineering education to separate ignition wires from receiver wires. Common sense should tell you that.
That said your reference to the spark is off base I think.
The spark shorts the inductive pulse from the coil and makes it a square wave.
A square wave is defined as containing an infinite number of odd harmonics. But in our case its a finite number of odd harmonics. the lowest frequency contained is the fundamental of the square wave while the highest frequency is determined by the rise time of the square wave. We can control the rise time by adding resistance to the spark lead. That's why we can use an unshielded spark lead and not have it interfere with our receiver. But with 2.4 we don't even need that because the resistance of the line is enough to stop interference of the radio.

dirty,

I didn’t wait until I got drafted. As soon as my college deferment expired, I flunked out. I got a letter from the draft board inquiring if I was still living there. That did it. I joined the reserves. That was in 1957 and I got out in 1965. By that time I had finished college, thanks to dad, and got no GI benefits since reservists are not vets.

Back to the subject at hand. That method of radio frequency interference you are describing is one of them our receivers are subject to. The other one is what’s coming from the spark. One of these days I would love to have some one sniff around one of our models with the engine running, with a 2.4GigaHertz horn connected to a spectrum analyzer and just see what is there. I am sure there will be bursts of RFI every now and then. The best bet is to just stay away from it.

By the way, thanks for keeping us safe while you were in. I did nothing except pray that I would never get activated. I never did.

Dan.

Rule 1. Do ALL you can to prevent a RFI noise problem. NOT the minimum.
Because sooner or later the laws of physics are going to bite you in the butt if you cheated.

If you will have problems depends on a huge number of factors. Someone mentioned you are running DC through your ignition battery wires. That is true, but when your engine is running the ignition module draws with every spark a little pulse of energy from the battery.
This causes little voltage fluctuations in the circuit, now you have a pulsating Voltage, still DC but the pulsating part has the same bad habit as pure AC - nearby wires can pick up some induction voltage (that is how transformers work).
Now most ignition system have capacitors to keep the current flow more constant and there is little to none fluctuation.
To answer the question someone would have to do some extensive tests to see which engine/ignition system interferes with which radio system under different installation distances....
So some never have any problems running the ignition and radio off the same battery, others had problems with just using some metal push rod.
It is always a good practice to be on the safe side and do as much separation as practical. Get a helper to watch the servos while doing a range check with running engine and different rpm settings

To the OP
Given the small weight of ign batteries, you probably could locate it at the firewall, and just move your (presumably heavier) receiver batter back a few more inches. Because the receiver battery is farther from the CG than the ign battery, and heavier, you may not need to move it aft much further to achieve the CG you want.

"Mr Moderator" I love it

I'm not going to post my resume but I have enough experience in model and full scale aviation to tell you that you don't have to worry about an igition and reciever battery interfering with your radio, especially a 2.4 installation.

Do whatever makes you happy, it's your plane.

I have to agree with that.
In small gassers I use the same battery for the ignition and the receiver.
I sure would not have tried that when I used 72mhz.
Time and new techniques change things.

In my experience I've not encountered such problems with 2.4 radios. I do keep some separation ( a couple inches or so), and keep my wiring segregated, but mostly for serviceability. As well, my observation has been that you don't see many guys flying helis at 72mhz.. look at how close the gear is crammed into those canopies. To conclude, I wouldn't say mount everything on top of each other, but wouldn't lose sleep over some components being a bit close together either.

I'm one of those guys who flew helicopters on 72mhz and never had a radio problem that I was aware of.

X2!
When I first flew heli's I was on AM!

+1 I also have both my batteries mounted on top of the engine on a shelf. No problems what so ever. I also do a range check with engine on and also make sure I have my fail safe set for low throttle slight up elev. 2.4 airtronics, faultless for 3 yrs now. Lucky? Maybe yes maybe no. Short leads are a good idea and why everyonegoes through allkinds of conumdrumsto savea couple of ozs of lead is beyond me.??? just add the lead and be done with it. KISS

Cool.. am assuming some type of measures still have to be taken to diminish possible interference, no metal-to-metal, that kinda thing. Not a heli guy, just an observational comment, it certainly is a tighter area to fit everything in..