Radio interference question(s)...
 

It's been a little while since I actually started I thread, so I thought I'd have at it....

Just kidding! :)

Maybe Terry and/or Ralph can help out with this one. The rule of thumb is to keep your radio equipment 12" away from the engine and ignition system right? Well then why is it that every time the magazines do a gas engine airplane, they get away with mounting the throttle servo on the firewall? Are they just chancing it and getting lucky? Is this something that could work for a while, then cause sudden problems later? It sure would be easier doing throttle linkage this way if a person knew it was safe.

Thanks for any input,
AV8TOR

RE: Radio interference question(s)...
 

In a few words, Modern Radios.
The "rules" were developed when we flew AM and ignition.
There many things that will reduce the safe range of your plane. You can fudge a few, but sooner or later you will be some place and the "fudges" are going to gang up with other things and plant your plane. The idea is to make the safest installation to give you the most headroom and keep you flying durning those times when the forces of evil gang up on your plane.

RE: Radio interference question(s)...
 

Thanks Terry. I was thinking along those lines. The area I am presently flying in is known for radio interference issues. Even with a new radio and a "tight" installation I get an ocassional little glitch from time to time, so I better play it safe and not take chances.

Take care,
AV8TOR

RE: Radio interference question(s)...
 

Here is a new case:
A friend is flying my own design ultimate with 70" wingspan and a DA 50cc.
The engines is great, the radio equipent is located away of the ignition and engine components. During the first flight we noticed that when any stick is moved in the Tx the response will delay as long as 1 second or more when the engine was running. The first flight becomes a nightmare...you will imagine..
But once on the ground we checked the radio and everything was OK. We went up to 6 volts. and the problems persist...

So there is no a problem of power from the servos, ( 2.400 Mha) , is a interference problem that occurs when the engine is running. The notorious thing here is that there are no glitches or strange movements, only a loooong delay in the rx to do what you mean with the Tx.

So much, that finally you moved the sticks and the servos almost do not move, but once the engine was switched off, the movements becomes as natural as ever.


After 2 days of inspection I passed by the workshop of my friend and discover he used a loooong wire from the servo to the throttle, thinking that the little plastic link at the end will seal the interference.

is this so???
I don`t think so, so now we are changin to a complete plastic pushrod. besides that there is no other thing that could affect the reception in the plane, there are no pull pull, no long wires along the fuselage, no wing wires, etc.

The strange thing is that I never saw that kind of behavior in a plane because of interference.

What do you think??

Tatolazo

RE: Radio interference question(s)...
 

It sounds like your friend might be using a PCM radio. The PCM radios will wait until they receive a "good" signal. Until they do, they will maintain whatever setting the last good signal was. PCM radios are generally not used with gas engines because they can mask an interference problem until it is too late. Please let us know if this is the case.

Good luck,
AV8TOR

RE: Radio interference question(s)...
 

So what about the gasser helis? All the electronics are pretty much packed in close to the engine. Go to the Century site and look at the Predator Gasser.

Steve

RE: Radio interference question(s)...
 

Simply put, you want to keep electronics that inherently generate noise away from those that can pick up noise. RF is fundamentally transmitted two ways - radiated emissions (given off in air), or conducted emissions (traveling through the wire between electronics). Think of it this way - ANY wire is basically an antenna. If RF is present (radiated), it can be picked up by that wire and then travels to the equipment that it is connected to. The electronics may be good enough to reject the noise, or it may wreak havoc. Energy can also be transmitted through a wire (conducted), say if your electronic ignition is connected to your receiver for some reason and the ignition is noisy. What usually happens on r/c aircraft is there are long leads (maybe a throttle servo up front) or in the wings, that RF is picked up by. It travels down the leads and causes interference with your receiver. This lead might just be the proper length to optimally pick up that frequency, or darn close.

RF energy falls of at the square of the distance in free space (air), so the further you get away, the better off you are.

Now, electronics can be pesky at times. :eek: Over time, wires flex, conductors fail, etc. A loose connection can cause rf to be emitted and hence a new problem arises. A spark plug cap's shielding may break down, etc.

Electronic equipment is getting better on all fronts, so that is undoubtedly the reason that more and more equipment is being seen placed all over airframes.

Michael

RE: Radio interference question(s)...
 

Good answer(s) and thank you.

RE the "antenna effect"... Yes, and the length could be 1/4 wave, 1/2 wave, etc. Then 1st order modulation problems, second... Tricky things those electrons. Guess I won't mount my throttle servo on the firewall!!! :)

Thanks again and take care,
AV8TOR

RE: Radio interference question(s)...
 

Most of the gasser Helis use the Bosch sheilded cap.

RE: Radio interference question(s)...
 

tatolazo
The first paragraph of your post, brought a smile. The time delay thing is not exclusive to RC Radio equipment! Seems like it is happening much closer to home[>:][>:]

RE: Radio interference question(s)...
 

We replaced the metal rod from the throttle servo to the engine for a dubro plastic pushrod...As it should be from the begining...and voilá...the plane is flying great.

He didn´t tell em he used the metal rod. I would never use one of them. Only told me that, after we switched from 4.8 to 6 v., later added a 2nd. pack, etc. but as soon as we take out the metal rod...the problem gone!!!

Those magazine articles were right this time!!!!

Thanks all.

Tatolazo

RE: Radio interference question(s)...
 

I was playing around a lot with the ignition I made. With the ignition running on the bench I tried to put a Futaba FM Reciever (Dual Conversion) and a GWS Naro (Single Conversion) at any place, even at 3cm of the ignition box, the spark plug wire or the spark plug and there is no interference at all. I tried to put the antena in the spark, no interference. I have done these tests on the bench using R spark plug.
With convencional spark plugs I can't use my phone and the calculator near to the bench makes sounds and print some numbers! :) (maybe messages from other planet)

RE: Radio interference question(s)...
 

Hi there lads, it seems to me as if there is a very well kept secret about ignition systems and radio interference . Just about everyone goes on about CDI as if there was nothing better..........well there is . It's called TCI, better known as inductive discharge ignition. So why is is it better? Well for a start you dont need screened leads. What, you say, then the voltage must be low with a small spark. Not so, as a well designed TCI system with ultrafast switching is every bit a match for CDI. I run 342cc weslakes with my system which have TWO 18 inch HT leads and are completely unscreened. They just have resistor plugs fitted...essential in any ignition system and if you can imagine a half size bipe flying a mile away and with the transmitted signal looking down the end of the aerial then that is a pretty good test. Well now why is it safer to run TCI than CDI? Consider How the ignition coils are actually made to produce their high voltages. With CDI the capacitor is charged up to at least two hundred volts and this is suddenly switched onto the ignition coil primary winding and you have a spike of voltage that initially shoots so high that the radio interference that it creates must be controlled. This first oscillation of the coil is so short that it contributes little to the resultant high voltage produced by the exponential decay of these oscillations in the coil. With TCI The voltage of the battery supply 6v or so, is just sitting on the ignition coil for a short period and then simply turned off. You still get the oscillations as the field decays but there is not the problem of the first oscillation going through the roof voltage wise. You could almost call it a soft start. The spike that I have been talking about is also more of a problem in the low voltage wires of a CDI system and this is a source of danger that you ignore at your peril. Anyway this old limey has been spouting long enough so I'll finish by saying that I have been designing the things for the last 22years and the proof of the pudding is in the eating. I have a quarter scale Stampe which has been flying since 1980 and is still going strong, although it now has the Quadra with my MK 10 ignition system fitted with ignition advance control.
I am a member of the Large Model Association of Great Britain and we are controlled by the Civil Aviation Authority and we have an excellent saftey record. Now I wonder if I can convert a few more of those chaps over TCI!!!!!!!!

Happy new year to you all and SAFE FLYING.

Codger.:):):):)

RE: Radio interference question(s)...
 

Ignitions systems in good condition do not have to emit radio frequency, but engines that has magnet and coil like captors can sometimes do it, magnet and Hall sensor are but safe. Never use metal wires from the engine to the model interior. In a big plane the better thing is fiber optic extensions or wire of stereophonic microphone. Good Luck:)
www.hpignitions.com.ar

RE: Radio interference question(s)...
 

Codger back,

Where in the hell did I get TCI from? Sorry I meant TDI.......Transistorised Discharge ignition. Just had a senior moment I'm afraid.

I use high power mosfets driven from Cmos Schmitt outputs, very effective. Runs on 6 - 8volts 40 kv and 1inch spark on the 342 weslakes using a honda coil and nearly half inch at 6volts on the modelectric coil which has been in my Stampe + quadra without trouble for many years.
There has been much spoken about inductive systems ie kettering system on these forums and you know what they say ,....a lttle bit of knowledge can be dangerous....... which means that most of the kettering systems spoken about have only come up with very basic circuits that leave a lot to be desired.
If the screening breaks down on CDI you are in big trouble and I have seen some VERY large aircraft at the La ferte Alais airshow in France which have shown signs of that before they came to grief. You know the symptoms, Throttle high --- control problems, throttle low and we have control again.
A WELL designed TDI system means reliability AND more to the point SAFETY.
There, thats put the cat amongst the pigeons........see you all.

Codger.:eek::eek::):):D:D[sm=thumbup.gif][sm=thumbup.gif]

RE: Radio interference question(s)...
 

To the Roland who E-mailed me, my reply to you is being returned as your address is not working. Maybe you typed in an error, try again.
Codger.