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Interference and 2.4GHZ

Old 08-19-2014, 10:04 AM
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dirtybird
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Default Interference and 2.4GHZ

For the purpose of this thread I am going to make an outrageous statement
It is impossible for the ignition of a gas motor to interfere with 2.4 GHZ system.



I know a lot of you don't believe that but it's true. Well maybe not completely impossible but it is so close to impossible that it can be considered impossible.
I am going to make two points..

First consider the way to spread spectrum system works.
In the transmitter or receiver there is a mathematical formula to develop what is called a pseudorandom number. It is pseudorandom number because a computer cannot produce a true random number:
during the binding process the number is transferred to the other device, receiver or transmitter depending on where it has been generated.
This number,now called the code, is used by the transmitter to determine what frequency to transmit on. The Receiver looks to see if the series of frequencies agrees with the code that the two devices agreed to use during a binding process. If it does not agree the receiver rejects the message. That is why your friend transmitting on exact same frequencies does not interfere with you. His receiver is looking for different code.
Now I ask you a question. If your friend, transmitting a on the same exact frequencies, does not interfere with you why would you expect the ignition noise that is completely random to interfere with your system?
My next point:
It is said that the ignition spark contains all of the frequencies in the spectrum. True. It contains all of frequencies from zero to above the frequency of light. So why doesn't it completely wipe out the band and completely block your system? Well perhaps it does. But consider this:
A motor running at say 6000 RPM produces a spark every 10 ms. But that spark only lasts for less than 1 ms. That leaves 9 ms for the transmitter to send the data to the receiver. 9 ms is a very very long time considering the electronics we have today, and the bandwidth available on 2.4. So the band gets wiped out one 1ms out of 10 ms. The receiver would just reject the noise and continue to get updated nine times out of 10 ms. With the bandwidth available on 2.4 you could easily update all the channels in 1 ms.


You are still not convinced?
Try this:
Remove the spark plug from your engine. Remove propeller and spinner.
Insert the spark plug in your high tension lead.
Install the spinner on your engin without the propeller, turn on the ignition, and the receiver and transmitter, and use the starter to spin the engine. Have someone else operate the controls and hold the sparking plug as close to the receiver antenna as you can.
You will find that your system will operate normally.


If you have a situation that looks like an RF problem, its not. You had better find what the cause truly is, or it would likely come back and bite you later.
Old 08-19-2014, 10:17 AM
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....

Last edited by Truckracer; 08-19-2014 at 09:18 PM. Reason: contribution to this thread not wanted or needed
Old 08-19-2014, 10:35 AM
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But Futaba says be sure all your receivers and servo's are 12 " away....... Better get your flak vest and helmet on
Old 08-19-2014, 11:00 AM
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Rodney
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I have to dissagree when you say it is impossible for 2.4GHz to be interupted by ignition noise. There is still one way it can happen, if the noise is so intense or heavy that it blanks out all (or most all) of the incomming correct data packets. I have seen this happen only one time but, while highly unlikely, it can happen as I have witnessed it. Up until that time, I also thought it was impossible and did hours of experiment in testing trying to prove it was some other cause without success. Finally, replacing the ignition module removed the problem.
Old 08-19-2014, 11:30 AM
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Maybe Futaba doesn't know what they are talking about. Only kidding. Dan.
Old 08-19-2014, 11:38 AM
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dirtybird
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Originally Posted by Rodney View Post
I have to dissagree when you say it is impossible for 2.4GHz to be interupted by ignition noise. There is still one way it can happen, if the noise is so intense or heavy that it blanks out all (or most all) of the incomming correct data packets. I have seen this happen only one time but, while highly unlikely, it can happen as I have witnessed it. Up until that time, I also thought it was impossible and did hours of experiment in testing trying to prove it was some other cause without success. Finally, replacing the ignition module removed the problem.
See point 2
Old 08-19-2014, 11:41 AM
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I sell and make parts for ignition every day and the one most common call I get for support is when I sell a G62 electronic conversion.

Customer says ignition works great but the servos on there plane go crazy, I tell the how to install the plug cap.


Some will call back and tell me it solved the problems and other I never hear back from.


Install your plug cap down to just where it touches the hex on the spark plug and crank the engine and see what happens.

Milton
Old 08-19-2014, 11:45 AM
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dirtybird
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Originally Posted by Truckracer View Post
Hi there dirtybird!

Can't disagree with anything you say here dirtybird. It just doesn't go far enough to explore possible interference with servos, etc. that are all low frequency devices that are still controlled by an analog pulse. These devices could care less whether the front end of the radio is on 2.4 GHz or any other frequency.

Not sure I agree with just having the plug in its cap for a test. This is almost like radiating the spark energy from an isotropic point. I would think the loose cap test would produce a better radiated signal.
I cant argue with the low frequency stuff. I am thinking I will convert to Sbuss system. It should be more resistant. I will get mine from FR sky though, Its just as good as Futaba and a lot cheaper.. They have an all metal digital servo for $40
Old 08-19-2014, 12:04 PM
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dirtybird
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Originally Posted by BadAzzMaxx View Post
I sell and make parts for ignition every day and the one most common call I get for support is when I sell a G62 electronic conversion.

Customer says ignition works great but the servos on there plane go crazy, I tell the how to install the plug cap.


Some will call back and tell me it solved the problems and other I never hear back from.


Install your plug cap down to just where it touches the hex on the spark plug and crank the engine and see what happens.

Milton
First of all did you ask what frequency they were on?
Many, many Zenoah engines were sold with no shielding of any kind. All they used was a resistor spark plug.
I have a G-62 that was converted to electronic ignition by Ralph. It does not have any shielding. I flew it a lot of times several years ago. Even on 72mhz.
How did you manage to screw that up?
Old 08-19-2014, 12:10 PM
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Originally Posted by dirtybird View Post
First of all did you ask what frequency they were on?
Many, many Zenoah engines were sold with no shielding of any kind. All they used was a resistor spark plug.
I have a G-62 that was converted to electronic ignition by Ralph. It does not have any shielding. I flew it a lot of times several years ago. Even on 72mhz.
How did you manage to screw that up?
The first thing I ask is what system they are using, All the ignitions I sell are shielded ignitions.

Now take that G62 that is not shielded and do the same test as I posted above, Put the boot on the plug just enough to hold it but do not lock it on the plug and crank the engine.

Milton
Old 08-19-2014, 12:42 PM
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Sorry dirtybird, but yours sounds like a layman's understanding of 2.4Ghz operations; just enough knowledge to get into trouble.

My brother was an electronics tech, and we would experiment for fun with different devices, from synthesizers to radar jammers. One predicate I learned in HS electronics is that ANY frequency can be jammed/swamped if one has enough power (wattage). I found this to be the case with police radar when it was first introduced.

Heli fliers on another popular site first noticed the odd phenomenon years ago. When their smart phones rang while on the flight line, and nearby helis would get suddenly skittish, they put 2+2 together and banned cell phones on the flight line. It seems that phones put out the strongest signal when making or ending a call. It wouldn't happen every time, but enough to give notice. Keeping cells off the flight line, or back inside the car, seemed to be the solution.
Old 08-19-2014, 01:27 PM
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dirtybird
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Originally Posted by eddieC View Post
Sorry dirtybird, but yours sounds like a layman's understanding of 2.4Ghz operations; just enough knowledge to get into trouble.

My brother was an electronics tech, and we would experiment for fun with different devices, from synthesizers to radar jammers. One predicate I learned in HS electronics is that ANY frequency can be jammed/swamped if one has enough power (wattage). I found this to be the case with police radar when it was first introduced.

Heli fliers on another popular site first noticed the odd phenomenon years ago. When their smart phones rang while on the flight line, and nearby helis would get suddenly skittish, they put 2+2 together and banned cell phones on the flight line. It seems that phones put out the strongest signal when making or ending a call. It wouldn't happen every time, but enough to give notice. Keeping cells off the flight line, or back inside the car, seemed to be the solution.
e

Well Eddie I dont have any relatives that are electronic techs but I happen to be an electronics engineer with more then 40 years of experience, some of it testing spread spectrum systems. now I dont know the exact implementation of the current systems. Would you care to enlighten me and point out where I am wrong?
Yes you can wipe out any system if you have enough jammer power but did you read point 2?
Old 08-19-2014, 01:37 PM
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dirtybird
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Originally Posted by BadAzzMaxx View Post
The first thing I ask is what system they are using, All the ignitions I sell are shielded ignitions.

Now take that G62 that is not shielded and do the same test as I posted above, Put the boot on the plug just enough to hold it but do not lock it on the plug and crank the engine.

Milton
I would like to do your test but I just had a pacemaker inplanted and am not to do much of anything for the next 4-6 weeks.By that time I expect you will have forgotten about it.
Why don't you do the test and post it on ytube?

And one more thing: To make sure you are not getting coupling to the servo leads. remove the servos and put a scope on the pulse outputs of the recaiver

Last edited by dirtybird; 08-19-2014 at 01:59 PM.
Old 08-19-2014, 02:21 PM
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Originally Posted by dirtybird View Post
I cant argue with the low frequency stuff. I am thinking I will convert to Sbuss system. It should be more resistant. I will get mine from FR sky though, Its just as good as Futaba and a lot cheaper.. They have an all metal digital servo for $40
Would that work, I thought Sbuss wasn't a high frequency digital signal with a decoder at the end but just serial pulse signals sent through one line and then "split" by the Sbuss servo unit (i.e. send pulse no Y to channel X) or Sbus servo which is looking for pulse number Y, so any noise on this system would be similar to individual servos plugged direct to the Rx.
Old 08-19-2014, 02:22 PM
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I don't know if the problem is in the servos, servo leads or the receiver and really do not care, I am posting real world facts that I have seen and have had customers tell me they had.

I am no way a electronic expert, just know what will happen.

Milton
Old 08-19-2014, 02:32 PM
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All Day Dan
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Dirtybird, be sure to tell your doctor that you fly RC and use an engine that requires a spark. There have been several guys in my club that had to give up ignition engines because it was interfering with their pacemaker and they felt it. Not having one I don’t know what the symptoms were but they avoid the gasoline engines now whenever there is one running nearby. By the way, they also had to bring their transmitter in to the doctor’s office to have it on while the pacemaker was being monitored. No problem there.Dan.
Old 08-19-2014, 03:09 PM
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Yes you can wipe out any system if you have enough jammer power but did you read point 2?
dirtybird, I respect your 40 years as an EE. As for point 2 and a spark lasting but 1ms, that may be so in a lab or with new equipment, properly shielded. Who knows how long spark propagation could occur with a poorly shielded, dirty, damp connection? Also, we're only interfering with a 100mw transmitter signal.

How do you explain the results of the heli fliers years ago? It's on the run ryder (one word) website.
Old 08-19-2014, 04:03 PM
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[QUOTE=All Day Dan;11863822]Dirtybird, be sure to tell your doctor that you fly RC and use an engine that requires a spark. There have been several guys in my club that had to give up ignition engines because it was interfering with their pacemaker and they felt it. Not having one I don’t know what the symptoms were but they avoid the gasoline engines now whenever there is one running nearby. By the way, they also had to bring their transmitter in to the doctor’s office to have it on while the pacemaker was being monitored. No problem there.Dan.[/QUOTE

I discussed this with my Dr. He assured me that the only thing that would affect it is a strong magnet held directly over the pacemaker. I ask him about this because I read on this wonderful internot that you should not use a chain saw.
He said I can even have an MRI which has been a no no before.
I guess they continue to make improvements.
Old 08-19-2014, 04:08 PM
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dirtybird
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Originally Posted by eddieC View Post
dirtybird, I respect your 40 years as an EE. As for point 2 and a spark lasting but 1ms, that may be so in a lab or with new equipment, properly shielded. Who knows how long spark propagation could occur with a poorly shielded, dirty, damp connection? Also, we're only interfering with a 100mw transmitter signal.

How do you explain the results of the heli fliers years ago? It's on the run ryder (one word) website.
I checked the spark duration with my oscilloscope and an RCEXL ignition. Its far less than 1 ms.
I will looh at the Ryder website
Old 08-19-2014, 04:11 PM
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dirtybird
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Originally Posted by eddieC View Post
dirtybird, I respect your 40 years as an EE. As for point 2 and a spark lasting but 1ms, that may be so in a lab or with new equipment, properly shielded. Who knows how long spark propagation could occur with a poorly shielded, dirty, damp connection? Also, we're only interfering with a 100mw transmitter signal.

How do you explain the results of the heli fliers years ago? It's on the run ryder (one word) website.
I checked the spark duration with my oscilloscope and an RCEXL ignition. Its far less than 1 ms.
I will look at the Ryder websit
I looked. Its about truck
OK I found the site. But would you provide a link? I dont want to spend all day looking thru that website

Last edited by dirtybird; 08-19-2014 at 04:17 PM.
Old 08-19-2014, 04:26 PM
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Originally Posted by FSki View Post
Would that work, I thought Sbuss wasn't a high frequency digital signal with a decoder at the end but just serial pulse signals sent through one line and then "split" by the Sbuss servo unit (i.e. send pulse no Y to channel X) or Sbus servo which is looking for pulse number Y, so any noise on this system would be similar to individual servos plugged direct to the Rx.
If its just one serial line the pulse needs an address to tell which servo to go to
Old 08-19-2014, 04:58 PM
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Originally Posted by BadAzzMaxx View Post
I don't know if the problem is in the servos, servo leads or the receiver and really do not care, I am posting real world facts that I have seen and have had customers tell me they had.

I am no way a electronic expert, just know what will happen.

Milton
++1!!

Dirty Bird, why do you negate everyone's experience at having encountered interference in their airplane installations of 2.4 gig radio systems?? You can preach all day long about the impossibility of interference affecting the 2.4 gig system, and provide all the proof you want, but you are NOT considering the other areas of the entire radio system where RF interference does penetrate and DOES cause glitching problems. For an apparently knowledgeable electronics engineer, you seem to be very close minded I am sorry to say.

This whole subject started in another thread, and frankly is getting tiresome. The only reason I follow it is because I feel we are somewhat honor bound to provide good info to the people that visit this forum, and stating that it is literally impossible to encounter interference on 2.4 gig radio systems is downright misleading and untrue.

AV8TOR

Last edited by av8tor1977; 08-19-2014 at 05:04 PM.
Old 08-19-2014, 05:41 PM
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....

Last edited by Truckracer; 08-19-2014 at 09:19 PM. Reason: contribution to this thread not wanted or needed
Old 08-19-2014, 06:15 PM
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This has been a very informative thread even with the banter. I have to say from my understanding of 2.4 that I agree with dirtybird. The areas of interference, by the discussions here anyway, have been by a means that is bypassing the 2.4 system, not going thru it. The "2.4" is the transmission of signal between the Tx and the Rx through the airways. Everything else such as servos, ign's, etc, is not a 2.4 signal. Digital or analog yes but not a band, therefore one can not say that a twitching servo is caused by interference of the 2.4 system. Merely that is the perception from a lack of understanding and a true cause will be found within the electronics outside of the Tx to Rx 2.4 transmission.
Old 08-19-2014, 06:26 PM
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Sorry, but my response to this is "Oh good God!!" The average person builds a plane or assembles an ARF, he installs a radio system in it, and because it is a 2.4 gb system, he is led to believe that he can ignore all the advice about proper radio installation because hey, "It's 2.4 gb and it's bullet proof!" as is being presented here.

Let me tell you, as he does the walk of shame, with his garbage bag in hand, and collects what is left of his airplane, I really don't think he cares exactly how his "2.4 gb SYSTEM didn't get hit on the high side; it got hit on the low."

I've said my peace, and I'm out of here.....

AV8TOR

Last edited by av8tor1977; 08-19-2014 at 06:28 PM.

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