Questions on RF Interference
 

I have a C&H Ignition on a large gas engine. The instructions with the ignition say not to use a metal throttle pushrod even if you use plastic clevis'. It also says to keep the everything including charge jack, related to the ignition, away from the receiver. I have a rather unique problem in that I need a very rigid straight pushrod between throttle servo and engine; and because of rewiring existing holes, the ignition battery charge jack is right next to the MPI receiver switch. A couple of questions:

(1) If I do range checks and everything is ok, am I OK or is this RF issue intermitten?
(2) I have been told a CF rod conducts electrical signals just like metal. Is this true or am I a little safer using a CF throttle pushrod than metal. I already have plastic servo arm and Hughs plastic clevis'.
(3) Even with a good range check, should I go to the trouble of relocating the ignition charge jack - removing, filling and repainting the old hole. The CDI unit/switch/battery are about 8 inches from the receiver and 5 inches from the receiver battery. Thank you.

RE: Questions on RF Interference
 

CH provides the caveat to avoid metal throttle rods in order to alert everyone that an issue with RF could occur in various situations. They also provide the direction that the user should do a complete range check to be assured there are no issues with RF. That range check should be done twice. Once with the engine running and once with the engine off. A difference in range of 10% or greater between the two checks would indicate that there may be a problem and should be looked into before flying the aircraft.

If there are no notable differences in range checks using a metal or carbon fiber pushrod, then you will be safe to fly providing you installed a break in the rod connections at both ends such as a plastic clevis or a ball link that is housed in plastic. I have been using both types of pushrods, C/F and metal, for years without issue, but the range check has always been an important part of the preflight.

Any of the better radios in use today should provide up to 150' or better in the range check with the engine running. If you are using a Futaba transmitter/receiver, ignore the manufacturer notes that a 50-75' range check will be adaquate. It's not and should be a lot greater.

Enjoy your plane,
Pat

RE: Questions on RF Interference
 

RE: Questions on RF Interference
 

You can never have to much seperation, shielding and never be to carefull installing an ignition

RE: Questions on RF Interference
 

I have always wondered if there was some kind of shieldingmaterial you could out over a long throttle rod or wires running from battery/switch?

RE: Questions on RF Interference
 

When doing a range check with the engine running, where in the rev range should the engine be, idle, mid throttle or WOT.

Karol

RE: Questions on RF Interference
 

All of them if you also want to locate any vibration induced RF issues.

RE: Questions on RF Interference
 

Hi,

The care you need to take with gas ignitions and rx installation is related to the ability of the rx to reject interference. All rxs are not created equal. Some rxs not only tolerate metal on metal but they will tolerate meshing metal gears under load on board the airplane without a glitch. Other rxs are very sensitive to any metal on metal.

If your rx is sensitive to ignition noise or metal on metal, maybe you should consider switching to a more tolerant brand or model

Hope this helps

Elson

RE: Questions on RF Interference
 

Elson,

In your experience which brand or brands Rx's are the most noise tolerant.

Karol

RE: Questions on RF Interference
 

Hi,

The FMA quantum is the most tolerant rx I have tested. It will tolerate a 1.5 400 mhz transmitter on board, and grinding metal gears under load (at the same time) to open and close nets without a glitch. This is a "naked" rx without the protection of a "faraday cage" and additional antenna filters. Most other rxs cannot tolerate this noise.

Elson

RE: Questions on RF Interference
 

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I know that you are deeply into RF, so my comments are not challenging your knowledge.

What do you mean by "open and close nets"? Edumacate me, please. <G>

RE: Questions on RF Interference
 

Hi Ed,

I use large RC planes for aerial sampling of migrating insects and other organisms in the research mode. Depending on the plane size, we have 18' to 29" dual nets mounted on the plane to sieve the air for insects. The mesh is about window screen size. There is a bit of added drag when these nets are opened aloft. We had to design a rugged but not too heavy gear box to open and close these nets when traveling at 60 mph.

Elson