Engine Interference/Noise with Spektrum DX7???
 

Hey guys yesterday I was tuning my OS 46AX when I discovered that the High Speed Needle bracket had broke off(previously damaged from a crash). The High Speed Needle was dangling but still secure enough for me to do some tuning and it didn't cause any problems. But today I was messing around with my Twist and all the surfaces responded to my inputs, but as soon as I fired the engine up and gave it some revs, nothing was responding to my inputs. Everything was twitching and wouldn't respond. My receiver battery and transmitter battery were fully charged. The antenna on the transmitter was bent 90 degrees like it should be, the only thing I could think was maybe there was noise coming off of the bracket since it was vibrating against the engine. So I killed the engine and everything worked fine, then I removed the bracket to see if I could eliminate the two metals from vibrating, but it still caused my controls to go haywire once the engine was running. My radio equipment is only about 2 weeks old and have never been in a crash. I didn't think 2.4 GHz technology was effected by stiff like this. The only other thing that was different from yesterday and today was that I didn't have my wing on the plane yesterday, but I removed the wing/disco'd the ailerons and it still had the interference. Im not sure what to make of all this. Also my throttle pushrod is a plastic pushrod, so there shouldn't be any noise coming off of that.

RE: Engine Interference/Noise with Spektrum DX7???
 

2.4 Ghz radios can still be affected by RF interference like this. Unfortunately many people are confused on this issue. 2.4 radios will not interfere with EACH OTHER, but RF interference can still affect them. Metal to metal contact can/will vibrate with the engine running and cause glitches in your radio that you are describing.

Ken

RE: Engine Interference/Noise with Spektrum DX7???
 

I've seen ignitions on gas engines cause issues on Spektrum radios but never noise off of a glow engine. I'm not saying that it can't happen though.

Still, I would look for some other possible causes. Could vibration from the engine be affecting the switch, a connection or something else? Do you have the antennas from the two receivers oriented perpendicular to each other? Is it possible that there is a problem with the receiver itself? Could you have a bearing or something failing in the engine to cause an unusual RF problem?

Did you try re-binding it?

If in doubt, call Horizon. They have great support for their products. Even if you have to wait for a receiver repair or something, it is better than losing a plane.

RE: Engine Interference/Noise with Spektrum DX7???
 

I looked at my setup and I think the battery was coming loose from the switch connector. I'll just have to wait for the new bracket to test it out and do another range check just to be safe.

RE: Engine Interference/Noise with Spektrum DX7???
 

Switches can be one big airplane destroyer. The switch itself can cause you heartburn. The connection between switch and battery is a real place for trouble.
I suggest you use heat-srink tubing over the batt-switch connector. In my larger and /or better models, I splice in a second switch so there is a double switch routing for those little electric fellows to travel. Then when the engine is running, and the model is well held down, do a "Mag Check" (real airplane thing for recips) by switching one switch off at a time. If the radio fails with a switch off, then you know trouble could happen. Your choice on just how brave you wanna' be! ;)

At the very least, tape over all those electrical connections with a good sticky tape.

RE: Engine Interference/Noise with Spektrum DX7???
 

First off, alot of people seem to think 2.4 Ghz radios are imune to interference, not true.
It could be the engine but I have to ask, was the receiver in that same crash?
I have had receivers that were in a crash that worked just fine until I fired the engine up. Hairline cracks will sometimes show themselfs under the vibration of a running engine.
PS: as hossfly suggested your switch could also cause this. Plug your battery directly into your receiver and see if it still does the same thing.

RE: Engine Interference/Noise with Spektrum DX7???
 

The reciever has never been in a crash, but I used some thin wire to hold the connector together for now until I can order some safety clips off of towerhobbies. Anyone got any recommendations on a particular safety clip?

RE: Engine Interference/Noise with Spektrum DX7???
 

On connectors like battery to switch or servo to extension, stuff like that I use a piece of 3/8" heat shrink tubing.
My LHS sells short pieces just for that purpose.

RE: Engine Interference/Noise with Spektrum DX7???
 

How close were you to the airplane? It could be you were over driving the receiver...it didn't become an issue until you fired up the engine.....what I suggest is to fire up the engine and walk away 10 ft. and see what happens...

RE: Engine Interference/Noise with Spektrum DX7???
 

Spektrum says opposite of that. http://www.spektrumrc.com/DSM/Technology/spekTech.aspx

RE: Engine Interference/Noise with Spektrum DX7???
 

I don't buy it for one moment.
They may be less prone to it but not immune to spite their claims.

RE: Engine Interference/Noise with Spektrum DX7???
 

Brett,
Yes, I know what Spektrum says. But that is a sales pitch. ANY radio signal is subject to RF interference. It's just the nature of a radio signal. Now it's possible that they can reduce the amount of interference that it gets, but it's still possible for it to be hit with RF interference. The DSM that Spektrum and JR use will basically ignore any signal that doesn't have the ID of the transmitter encoded in the signal. BUT....... In this case if there is metal to metal contact creating RF signals it can be the stronger RF source and the signal from the transmitter will never get to the receiver. Therefore the receiver will never get communications from the transmitter and will act in the same manner as the original poster stated.

Even though a model uses a newer 2.4 ghz radio, all of the same methods and techniques used for older 72 Mhz radios to avoid causing RF interference need to be followed. To not do this thinking your radio is immune to signal interference is a recipe for disaster.

Ken

RE: Engine Interference/Noise with Spektrum DX7???
 

I guess I should have said Spektrum claims ...;)

RE: Engine Interference/Noise with Spektrum DX7???
 

Metal to metal contact on or around an engine is famous for causing interference.

Make sure that your throttle linkage does not have a metal clevis in contact with a metal throttle arm. Use something else to isolate the pushrod from the engine itself.

RE: Engine Interference/Noise with Spektrum DX7???
 

We also had a Spectrum seriously effected by noise from an ignition module. Yes, the 2.4GHz units also follow the same laws of nature that the other radios do, they can be effected by electrical noise, it is just that there is not as much chance as for the 72/75 MHz units. As to one of the comments above that the radio might be getting swamped out because the transmitter is to close: if so I'd sure get me another receiver as this will not happen with a well designed receiver and power levels that our RC transmitters put out, especially the 2.4GHz units.

RE: Engine Interference/Noise with Spektrum DX7???
 

I doubt there is much interference in the 2.4GHz band generated by RC model components. Low pass filtering is inherent in all of the electro-mechanical interference generating systems. You have to try pretty hard to get any kind of RF power up into the 2.4GHz band. In addition to the extremely high frequency, spread spectrum modulation provides an additional resistance to interference (and jamming, which is why the military uses it).

RE: Engine Interference/Noise with Spektrum DX7???
 

It doesn't have to be in the 2.4Ghz range to interfere. It only has to be a strong enough resonant frequency to partially block the signal.

RE: Engine Interference/Noise with Spektrum DX7???
 

That doesn't make any sense. If you can't get RF energy up into the 2.4GHz band, you can't interfere with a signal in that band.

RE: Engine Interference/Noise with Spektrum DX7???
 

Wouldn't overtones, etc. come into play?

Your primary RF freq would not necessarily be in the 2.4mHz band, but a lower primary may produce a resonance overtone smack in the middle... Granted that the likeyhood is not all that great of this happening, but given a LOT of RF noise couldn't it?

On 72Mhz I've had engines send my RX nuts when the engine hit a specific RPM range, and there is no way that the engine would be rotating at the same 72mHz rate... yet even with filtering my radio was still overpowered by the engine.

RE: Engine Interference/Noise with Spektrum DX7???
 

In Missileman's theory the proper term would be "harmonic" and they could get up into 2.4 range. Strong enough to interfere? I honestly don't know. The signal source is in close proximity to the RX. I do know that "spread spectrum" is NOT a valid defense as it only means the radio selects (in the case of Spektrum) one pair of freqs per flight. After that it sticks to those freqs and they are vulnerable like any other. Since Futaba hops from one to another they would be less vulnerable. It is simply ALWAYS a good idea to build to the highest standards that you can for safety sake.

All that said, there should be a much lower possibility of interference using the new 2.4 GHz systems but NOTHING is bullet-proof.

RE: Engine Interference/Noise with Spektrum DX7???
 

I should have said harmonics, Bruce is right. I know some of the theory but I really don't understand it well enough.
In practice I have only had a 2.4 Ghz radio interefered with once and that was from a 2.4 Ghz cordless phone of all things almost cost me a helicopter.

RE: Engine Interference/Noise with Spektrum DX7???
 

Thank you! I blanked out on the term.

RE: Engine Interference/Noise with Spektrum DX7???
 

This is actually a very legitimate source for 2.4 Ghz interference. There are a BUNCH of devices that are not RC related that operate in the 2.4 Ghz frequency ranges. Some that jump immediately to mind are computer wireless communications (Wi-Fi), telephones, video equipment, high speed data transmission equipment, as well as many more not mentioned. Most of the devices that are computer related are "Spread Spectrum" certified which means that they will "work and play well" with other Spread Spectrum devices. Our radios fall into that category. But for those devices that don't fall into that category they can and WILL interfere with our radios. I know this one for a fact. I build and manage computer networks for a living. I have some long range (up to 45 miles) wireless networking equipment that operates on 2.4 Ghz. This equipment broadcasts on a very narrow band when it's mounted on a tower, but if this were beamed across an area where a flying field was located it is possible that it could interfere with an RC radio.

Some items like telephones and video equipment have already proven to be able to interfere with our radios.

Ken

RE: Engine Interference/Noise with Spektrum DX7???
 

And remember (those that may have forgotten) 2.4 GHz is more than a specific frequency in our case. It is a BAND of multiple frequencies and it is left up to the individual equipment designer to determine exactly which freqs the equipment will operate on or choose between or hop about on and in what sequence. MANY variables. Futaba and Spektrum may not be even using exactly the same frequencies but I have not looked.

One nice thing about Futaba:In the US, FCC part 15 on unlicensed systems in the 2.4GHz bands permits more power than non-hopping systems. The limit is increased from 1 milliwatt to 1 watt or a thousand times increase. The FCC prescribes a minimum number of channels and a maximum dwell time for each channel.

Yes, I like Futaba. But the Spektrum stuff works OK too. Not trying to start a war here so please don't go there.

RE: Engine Interference/Noise with Spektrum DX7???
 

To answer a question, there is no metal to metal contact from throttle pushrod to engine control arm. The arm is plastic and the control horn is plastic. It may have been something totally different then metal to metal noise because I tried keeping the High Speed Needle away from the engine to avoid any contact and I still had the glitching. It may have just been that the battery connector was on the verge of becoming unplugged from the switch connector that the added vibration was enough to open and close the connection. To answer another question I was a foot away from the plane with my transmitter in hand and antenna bent 90 degrees as normal. I can't troubleshoot at the moment since I removed the engine until I get the new HSN bracket along with some safety connectors I ordered. Once I get everything put back together Im going to do a bunch of tests to make sure it was just the connector coming loose and not something wrong with the receiver or transmitter.