I know I need to keep the engine and ignition 20" or so away from any servo/receiver/wire/etc, but.... Could I put the switch harness for the ignition battery right next to the ignition switch for the receiver?

No!

Suggest you keep the ignition switch on or forward of the firewall. The receiver, servos and rest of the radio gear can be kept minimum at 12" for all sources of ignition. I always wrap the servo and switch wires with alluminum foil and had no interference problems.

Wrapping anything with aluminum foil does nothing unless one end of the foil is grounded. If it's not it acts like an antenna and actuall collects static.

Oh all right, I'll put the ignition switch below the firewall....

Here's an outside thought.

Pick up an isolater from I4C or EDR. Both will RF isolate the servos, switches, and batteries from the receiver. It will also give you the ability to run your receiver on a standard 600ma battery for hours while you use higher rated battery packs for ignition and servo drives. It's your choice if you would want an amplified isolater or not.

The isolater also serves as a high current electrical bus and you will not be able to draw down the drive battery to a point that will cause the receiver to drop out of the loop due to low voltage, provided your using a separate Rx battery.

They're not cheap at around $80.00, but what they do can save an airplane. Especially an airplane using digital servos and a PPM receiver, which can be more susceptable to noise feedback from the servos.

Just a stray thought.

Pat

I am getting glitches in my radio system and am trying to figure out why. Ignition electronics are all at least 18 inches away from the reciever etc. I did notice that the spark plug wire has been rubbing on the cowl or something and has worn away most of the steel braided wire that covers it in a spot about a half inch long. How sensitive is the radio system to a small amount of the steel wire that is missing? Do I need a new wire or can I just put electrical tape over it? Also, I have the throttle servo mounted on the fire wall and the linkage consists of a ball link and a 2-56 steel rod. Will the nylon ball link and nylon clevis isolate the servo from interfereing with my system?
Thanks for any help
JLS

You can patch the hole in the insulation by laying on a thick coat of Pacer Technologies Zap-A-Dap-A-Goo.

The 2-56 steel rod is a bad idea, as it can bring any EMI into the radio compartment. Look for a nylon or plastic replacement.

Jim, our club members have used that method on servo wires upto 6 feet long !!!!!!!!!!! and had no problems whatsoever.

But still I would like to know how to ground the end of alluminum foil.

Lots of differing replies on this thread, but the simplest thing to do, is to mount the IGN switch on the side of the fuse right behind the cowl, and mount the receiver switches as far back as possible on each side of the plane. Keep ALL IGN related components as far away as possible from ALL radio related components. There is no magic number of inches for this. There is no 20" rule, no 12" rule. If you can separate these components 48" then do it. Obviously you wouldn't put everything in the tail to keep them away from the IGN, but as far apart as practically possible is a good rule. If this plane is an aerobat with a canopy like an Extra, I would mount them on the sides right where the canopy meets the turtle deck. Done this way, there would be no need for opto isolators or other trinkets that are not needed. Metal rods on throttles are a definite no no. I use Sullivan precision rods. They are a black CF impregnated nyrod with a white outer sheath. They do not expand and contract as much with temperature like standard nyrods do. They also do not contain enough CF in the plastic to transmit EMI or RFI. I also read about patches on high tension leads...not advisable...replace it...if the outer shielding is compromised it can lead to a crash. Replacing a lead is not that expensive, but a crashed model is. Ask yourself if it's worth the risk. When I look at my big gasser the answer I give to that question is definitely NOT! To keep the high tension lead from chafing wrap a small piece of the fuzzy side of some velcro around it. I separate all wires going back to the tail a minimum of four inches...don't bundle wires all together...that is asking for an EMI problem. EMI is electro magnetic interference, and it's caused by electrical (magnetic) current passing through the wires which create magnetic fields. Putting these magnetic fields in close proximity to each other can result in 'cross talk' between the wires. It is a rare occurrence, but it's just good practice to eliminate this possible problem from the equation. On long leads use 22 awg HD extensions. It carries current better, and generally this wire has thicker insulation which also guards against possble EMI. Like Jim said using metal 'shielding' does nothing unless it is grounded. With a well thought out radio installation that is neatly done, I can see no reason for shielding of the wires. Patience and time spent on the radio install pays big dividends with these planes. I spend almost as much time on a the planning and actual work on a radio install as it takes me to cover one, and that's a bunch of time. One last suggestion, if a problem is found with a wire on the radio system or a high tension lead on an IGN, it belongs in the trash, replace it...don't try to patch it, or rig something up...it's just not worth it. By throwing spent items in the trash and replacing them, it will keep you from bringing the trash can to the crash site. Hope this answers your questions.

A professor in electronics, living far from town wrote in a paper, how to make a good TV antenna, he wrote about reflector, director, 1/4 lambda spacing etc and ended up saying "my son defies that and have put all kinds of alluminum pieces, including kitchen utensils on the antenna and gets perfect TV reception with NO INTERFERENCE".

Moral of the story:

For an aeromodeller, practical, proven methods are better than the theory in text books.

With the throttle servo mounted on the firewall, a good conductor of interference exist via the servo wire. With the servo right in the area of high ignition noise, the throttle linkage won't have much effect.

You can cure this two ways. Use one of the available optical isolators that use fiber optics for the link or move the servo into the center of the plane and use a nyrod type of connection.

Thanks guys for the replies. I have done several things wrong with my setup. As always, I have learned more on RCU in a matter of minutes than I have over the last couple of years just "asking around"
Thanks again,
JLS

JLS,

Good Luck. If you put an opto-isolater in, I don't think the i4c product is what you want. It is basically a power buss separating servo and receiver power. The signal wire is not isolated like other products.

ML

ZM2000:

Grounding aluminum foil is practically impossible. I used that statement to show that no matter what a wire is wrapped in it does no good unless one end of it is taken to ground, ie, the engine case, If left ungrounded the foil acts as an antenna and can collect static. If you don't believe me ask any ham operator that knows anything about antennas.
Think about your antenna cable on your TV. It has a shield on it that is grounded on both ends so that it can be used as a conductor for the tv signal. If one end is left ungrounded, it acts as a shield to take away all RFI that is picked up, so therefore your tv would not receive very good signal if at all.

Hrm,
This is bringing up another concern for me, the smoke pump. I had thought I could place the pump way up by the engine, next to the smoke tank but since I need to run a wire from the receiver to the pump its sounding like I need to place the pump towards the center of the plane away from the ignition...?

JIM

Thank you very much for the grounding information. I will use it for advantage. Indeed one learns a lot from RCUniverse.

Thanks to all who write in this forum.

Definitely you need to do that.