zope_pope

Is it a bad idea to run the Ignition Battery on top of the RX battery? Do i risk Rf noise to the receiver?

Meesh

My Feedback: (135)

Although I've never done it, it doesn't sound like a good idea.

I know for my PST Jet Turbine, the manual states that if the ECU and Rx battery must be together, you should mount them end to end and not stack them. Must be something to it.

Bob

Jake Ruddy

My Feedback: (40)

Well.... I don't really know what the correct answer is.. some people seem to think it's a bad idea.

I have them stacked with foam under and between the batteries to achieve my CG. I have 8 gallons of gas through my setup in the last 3 months like this. I dont know how many flights that translates to... but I usually use 16 oz per flight so if you do some math its a fair amount of flights . I have never once had a problem with this configuration.

I know several other people who have this setup as well with no issues.. one other guy had over 400 flights on his plane b4 it went in for a non related issue.

my 2 cents

Geistware

My Feedback: (16)

Putting the RX and Ignition packs together is not considered good practice.
I have done it successfully.
It all depends on the quality of your ignition grounds and the quality of your ignition unit.
If you are producing very low noise, it will work successfully.
You will never know until you test it.
Remember, if your range with the engine running is 90% of the engine off condition, then you should be OK.

AirWizard

My Feedback: (3)

I tried it using a DA50 and had RF problems. When I seperated the battaries the problem went away.

hardtop351

yes you will get rf noise cutting through your reciever. i have a 30% extra 300 that used to run a spark ignition engine. ive since removed the ignition system due to the pcm reciever suffering badly from noise. if you do want to run an ignition battery....keep it right up the front near the firewall. and as far from the radio gear as possible and keep anything wired to it like switches up the front too.

a good rule of thumb is to keep AT LEAST 12 inches of space between ignition system components and your reciever.

hope this helps

craig

zope_pope

Ugh, the stuff i didn't want to hear... I am running a da50, so I am guessing i'll have to just find another way to shift the cg aft. The only problem is, I just went out and replaced the wing and stab tubes with carbon ones and the airplane is more nose heavy than ever! Time to move the rx battery even further aft. I guess there is nothing to isolate the noise created by the battery to shield the interference. Any suggestions are welcome. Thanks!

zope_pope

How about this?

Placing the ignition and ignition battery side by side. Will this increase the amount of RF noise that the ignition system puts out? I am trying to get the longitudinal axis balanced by moving weight to one side. Thanks!

NM2K

My Feedback: (14)

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The engine battery does not create the noise that is the problem, in this instance. It is the wiring of the engine battery that runs to the nose of the aircraft that is acting as an antenna/transformer and is picking up and relaying the interfering electromagnetic waves to the vicinity of the receiver. Capiche?

The receiver operates in a noisey environment. There are many sources of electromagnetic radiation all around us at all times. The amplitude level of this noise in our environment is known as the "noise floor". This noise floor varies minute by minute in every location in the universe. For your receiver to "hear" your transmitter signal, the signal must be a certain amount louder than the noise floor.

Anything operating in your airframe that creates electrical noise, whether it be intermittent metal-to-metal contact, your servo motors sparking or your ignition (spark), will contribute to the level of this noise floor (it will increase, while your TX signal stays roughly the same). This means that the difference in signal level that your receiver has to work with (remember, there is a minimum level signal to which your receiver will respond) diminishes. This will decrease the system's range somewhat. Add enough signal noise, or enable the existing noise to reach your receiver, and you have an untenable situation in a hurry. Separate those batteries and keep any ignition wiring as far from any other wire in your flight system as you can. Distance is your friend.

So, you're at the field and the batteries are on top of one another and you're flying just fine. So what's the big deal? Well, Bill's dad has been restoring an old Fifties-something Ford bread truck. He just finished changing out the spark plug wires with nice, hot firing, solid copper ones. Boy, it sure starts quickly now!

Wait! There's Bill's father driving the restored Ford bread truck into the field's parking lot.

Someone yell's, "I ain't got it!" Is it your model?


Ed Cregger

ifshnee-RCU

My Feedback: (1)

If it crashes -- you shouldna done it!

pe reivers

Good post Ed, [sm=thumbs_up.gif]
Whatever the reason not to separate the components, it places the burden of extra risk on the shoulders of the guy that knowingly did it.

Rcpilot

My Feedback: (78)

Sounds to me like Zope Pope is trying to move his ignition battery back to get his CG right. The plane is currently nose heavy. Your one of the lucky ones. A nose heavy plane is 50 times easier to fix than a tail heavy plane.

Whats the ignition battery weigh? Couple ounces? Put that sucker up on the engine box as far from the RX and all RX components as possible. A couple ounces on the nose is EASY to fix.

Remember, generally, there is a 3:1 ratio on the plane. For ease of mathmatics, lets say you've got about 1 foot sticking out in front of the CG and 3' sticking out behind the CG. There's your 3:1 ratio. 3 ounces on the nose will cost you about 1 ounce in the tail--usually a lot less, but this is a "rule of thumb".

If the situation were reversed, and you had 3 extra ounces in the tail--it would cost you around 9 ounces in the nose to balance it. Thats why tail heavy planes suck to balance. It's darn near impossible to get 9 ounces of weight in the nose without adding lead.

Zope Pope has a nose heavy plane.

Put the ignition battery up front and away from your RX and RX batteries--where it belongs.

Did you use a pull-pull rudder? There's your fix. Put the rudder servo in the tail and use a short 4" linkage for a push/pull setup.

Already got the rudder servo in the tail? Then move your RX and RX battery back to the tail. This will not only solve your balance problem--but you won't have to worry about RF interference. Ed Cregger said, "Distance is your friend." He's right. That was an excellent post Ed.

Moving that ignition battery back to balance a nose heavy plane is the absolute LAST thing I'd ever do.

It's not that bad though. You are lucky. At least it's not tail heavy. [sm=thumbs_up.gif]

zope_pope

Alrighty, RCpilet is right. Nose heavy the plane is. To make it worse, I just got dumb and swapped the tail wheel for CF and the stab tubes. LOL. Now I have even more of an issue. Good news is I moved the Ignition battery up front on the outside of the engine box and then moved my RX battery about 4-6 inches back, and voila it is balanced. Unfortunately it is balanced at the stock recommended location, and the whole excercise was to try the model a little bit further aft, but atleast I now have a lighter airplane, that is balanced, with less chance of RF interference. It is a great flying airplane at the moment, but just a tad bit aft would make it perfect.

It all makes sense, the noise floor, etc. Thanks for the technical knoweledge guys. Hopefully I'll get to fly the model, but I just checked the winds and OUCH!! 24 gusting to 32. I wouldnt fly full scale in this weather and my model is about 160 times lighter. Hopefully weather is different at the field. See ya.

Rcpilot

My Feedback: (78)

Yank the CF tailwheel and put a steel unit back there. That will move your CG back a bit more. Save the CF for another plane.
[8D]

Tired Old Man

My Feedback: (1)

Although I've done it and gotten away with it, it's definately not the best idea. Why invite trouble if you don't need to?

Jake Ruddy

My Feedback: (40)

All valid points... like I said I didn't know the correct answer. So it appears we now have it

That plane is now sold.. so lucky for me I dont have to do a bunch of work to change my config and keep it tail heavy... already has a heavy tail wheel, servos in the tail, 3 stick on lead weights, CF Spinner, and batteries in the back half of the plane haha.

zope_pope

Holy Crap dude. Did you have twice the recommended engine size?

Jake Ruddy

My Feedback: (40)

Well truth be told now that I think about it... the plane does call for 2 rudder servos in the tail and I only used one good one... but yes I have a pretty big engine on it.

I also ran out of gas once right after I pulled off the end of the run way since my first rushed landing was too fast I needed to go around again. Needless to say I should have just stayed on the ground.. I broke the firewall and added some extra weight with the repair.

I could have easily moved the battery closer to the tail but I found a sweet spot with both batteries in one spot and didnt want to start changing things since my range checks were always fine.

lmoreira

How is the distance that you put???

captinjohn

AirWizard: How far apart did you place the battery pacs? Thanks from Imoreira and myself. Capt,n

Jezmo

Gotta love them Spektrums. I don't know what interference is anymore. Some guys with Spektrum radios are even using the same battery pack to power both the ignition and receiver with absolutely no problems. My cods aren't that big though. I am thinking I'll stick with seperate packs.

Bob Pastorello

My Feedback: (198)

I have THREE setups on JR/Spektrum 2.4 using the SAME battery for everything (A123's).... and I don't have big ones, either. It's easy to use after testing proves capability, and I did that before anything flew....

pe reivers

you are a brave man Bob. Knew it from the start.

crazyjoseph

My Feedback: (3)

I have done it with a zdz 80 lion batts over 400 flights no problems
Also DA 100 1 inch apart over 300 flights no problems