Ignition interference
 

I have a model with a Titan SG 23 (zenoa) gas engine where the ignition severely interferes with the radio equipment. I have done anything I possibly can do to reduce possible problems with the installation but interference persist. The range is verry low when enginen is on. Maybe 1/5th of the normal range. I still have not flown the model due to this.

From tests I have concluded that the interference mainly comes from the servo wires (wich are a bit long). The next thing to try is electrical filters on all the servo wires. I’m looking for ideas on what to use here. I would be happy if I could get advice on both how to solder my own filters and what type commercial filters there are.

I understand the interference can come two ways. One is through the servo wires and into the receiver. The other is through the wire and directly to the servo causing the servo to have some stochastic behaviour. Should there perhaps be a filter in both ends?

I’m happy for any advice I can get.

/David

RE: Ignition interference
 

Reko, have you checked to assure you have a resistor plug?
Check the plug wire , is there any cracks or rub spots? Is the spark plug cap tight on the plug?
Is the ground wire tight.
I know you do not have any metal to metal connections, but do you have any metal that can vibrate against metal. I had a RF problem and it was a tail wheel assembly that drove me up the wall once.

Filters are good once you find the problem, but I would not rely on filters to eliminate the problem.
Good luck
Wayne

RE: Ignition interference
 

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I agree with Wayne.

Also, the state of tune of your receiver can play an important part in rejecting RFI. Is your receiver recently made? Has it suffered a crash or any type of failure? Have you substituted another receiver and suffered the same results.

Some folks today mount their receivers with thin foam tape. This is not a great idea. Yes, I know the heli boys do it, but that does not make it the best mounting method. The receiver should be suspended in loosely packed "foam rubber", not plastic foam.

Another thing that I look for, besides the points that Wayne has raised, is the type of receiver being employed. I worry that I am going to come across someone trying to use a micro receiver that is intended for close-in electric flying in a larger model. This could lead to disaster.

A tune-up never hurts. If you have a time of the year when you are not flying because of the weather, send the Tx module and the Receivers that are used with that Tx module back for a tune up. While most equipment these days will work fine for several years without requiring a tune-up, using this equipment in an ignition engine environment raises the bar of excellence that is required to function properly. Check your Tx antenna and make sure that is properly secured in your Tx. You would be surprised how many times I have discovered a modeler's radio problems was attributed to a loose Tx antenna attachment deep in the Tx case.

Good luck.

RE: Ignition interference
 

Get out your electric drill and twist those servo wires. Teh twist doesn't have to be a lot but twist them to get them to length and to maybe have one turn per 20mm. The second thing I would do is make sure the antenna is well away from the servo wires.

RE: Ignition interference
 

Hi. Thank you all for your suggestions. Unfortunately most of what you have suggested already is checked. The spark plug is of “R-type”. The ignition cable and plug cap is also shielded. I suspected there was be a bad connection somewhere in the plug cap, causing extra sparks, but I have checked this without finding any faults.

I have tested two different receivers. Both of high quality. On was ppm the other pcm. Same result [:o]
The antenna is directed away from the servo leads.

I feel I have tested everything but filtering the servo leads. Hence my question of filters. I should add that the airplane is not of the conventional type. It’s a canard wing where the engine Is placed in the rear. I have 4 servos in the wing and the receiver is placed in the fuselage. The cables to the wing mounted servos are long and passes about 12-15cm from the motor. Due to this unusual configuration I think filtering the servo cables is important.

So back to my original question. What type of filters are there that I could use? Home made or commercial. I know the power box from duralite is one possible solution but it’s a bit expensive, and it only filters the receiver from getting interference though servo leads. As I have heard, the servos them self might need filtering.

thanks
/David

RE: Ignition interference
 

REKO, I STILL say you need to find the problem before you go to filters. Take one lead at a time loose from your Rx until you find the problem, then use filters as a safe guard, not a solution.
Go to:

www.emsjomar.com/SearchResult.aspx?CategoryID=4

They have the best filters in my opinion.
Wayne S.

RE: Ignition interference
 

I doubt that filters on the servo leads will help you. Your receiver has bypass capacitors in it to remove any pick up in the leads.
Here is another test you can make:
Remove the spark plug from the engine but leave it connected to the plug lead. Wrap the spark plug with aluminum foil completely enclosing it.
Shut off the gas from the engine, turn on the ignition, and with the spark plug hole open spin the engine up to speed with a starter. It might be a good idea to remove the propeller,too.
If the problem goes away you have a vibration problem.

RE: Ignition interference
 

I know you disagree, but I still say to twist your servo leads.

RE: Ignition interference
 

David,
There are a list of things I do when installing a gas engine.
I think if one follows these steps then the chances are the radio noise/interference becomes much less.

*receiver batteries, all the switches and all the servos must be atleast 30cm or 12" from the engine, more fare back is better.
*a resistor plug and resistor plug cover must be used, or the metallic type as it was on the old 3w:s
*the ignition wire must be shielded or for R/C use or better wrapped all the way with copper/ aluminium tape
*the firewall should be covered with thin aluminum sheet or something similar
*every metallic joint should be fastened and glued so that it can not vibrate and cause the radio noise.
*excessive vibration caused by a unbalanced prop or prophub, or rough running engine can also cause radio noise

If nothing helps then I think a conversion to electronic ignition will do it.
I know CH ignition is great as I have used it but I have also heard very good things about Runtronic which is locally available in Sweden.

RE: Ignition interference
 

I had the same problem with a Great Planes Ultimate 160 with a BME 50. Like you, I tried everything. I finally sent the ignition box to CH and they put a billet type connector on the spark plug lead. Tried it again and the problem was cured. Hope this helps you.

RE: Ignition interference
 

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Good advice.