Is the Spectrum receiver totally immune to noise?

[rdlohr]

I've been seeing a few nice new birds that have this receiver in close proximity to either the ESC lines and/or the motor like this receiver is completely immune to noise and no longer requires isolation from high current, noise generating components such as the ESC and the motor.

The battery, ESC, and motor all have high current levels, upwards of 30 Amps running through them and they inherently create large magnetic fields that I feel should not be near any electronics that we are counting on to control our helis.

This just seems like bad practice to me and I'm afraid we are giving the newbies the wrong guidance here...

[PeterV]

Yep for sure!
There is nothing about the DX 2.4G's that is of any help to local interference/noise. In that respect they are no different than any other RX.

The bottom line it keep ALL RC stuff as far away as possible from the other power devices - more so the motor and ESC.

The biggest problem I see is the "I did this and it has never been a problem", eg put the RX on the ESC.
That is just LUCK. Not true proof of anything.

Glitching is a very immeasureable event. It happens...it doesn't...some people who use bad placements of electronics are lucky, others are not. Even good placements can be 'unlucky'.
But electronics/physics is a finite and known science. So you just don't do things that oppose those guidelines. Otherwise you increase the odds of trouble!


PS: The title should not have said "RF noise"....just "noise". RF meaning Radio Frequency - HF/VHF/UHF etc.
Even 50Hz can radiate and be 'noise' (any alternating wave can radiate and/or create 'noise' in the right circumstances)....but it is a 'power' frequency, not RF.
ESC's I think up to/in the 400Khz range.

[CHOPPER BOB]

maybe this will help most or all noise that our helis create is in the same freq that fm radios listen on dsm radios do not hear this noise they are on 2.4gz noise that would glitch a fm or ppm, pcm that is why you will see more setup done like this the vids on the horizon page explain this better :D

[PeterV]

This thread is not talking about 'airwave RF noise'. It is about the fact there is 'local' noise generated ON the heli - and that is what 2.4g systems don't reject any different than any other RX.

But too many people seem to think the 2.4g means ALL noise has little or no effect. WRONG.

[CHOPPER BOB]

yes I know thats why I said create as I have afew radios that use the 2.4 gz freq efi is not in this range the guys at the local clubs have started to see that the glitch is gone with these radios I am useing these radios in my 1/5 gas trucks and my elect boats 45in and 60in gas with no glitchs all that I am saying is you are less likely to have a glitch with these radios but mounting should be done with noise in mind :D

[KamikaziRcPilot]

The only interference issue I've seen so far was caused by a 2.4ghz on-board camera. It just saturated the receiver to the point where it wouldn't work properly.

[rdlohr]

Thanks for the response. I removed RF from the title because I did mean all as was pointed out.

[Funky]

I had major glitching when I first began flying with a JR 6102 and FM receiver. It caused 2 major crashes within the first 2 weeks I flew. I tried moving things around, but it only made the glitches smaller, it never got rid of them no matter how hard I tried. I got used to a few glitches each flight and just tried to keep it up high enough that it wouldn't glitch itself into the ground. I was averaging maybe 15-20 glitches every 6 minute flight.... some small, some big. After I spectrumized my 6102 the glitches stopped. I have not seen a single one since. Since then I have wires hanging everywhere in 2 Rexes, a Blade and a Mini Titan and have not had a single glitch since the conversion. I am not supporting bad wiring, but for me, all I do is seperate the electronics the best I can, zip tie them up and fly. No more Worries, that first flight without a single glitch was like a dream compared to what I was used to :wink:

[rdlohr]

I am not supporting bad wiring, but for me, all I do is seperate the electronics the best I can, zip tie them up and fly.

Thats pretty much what I am advocating. Place your components following the proper placement rules and hope for the best. This won't assure zero glitches, but it gives you the best odds. (and don't use FM any more!)

Rick

[robmoney]

I think that the frquency band the DSM operates on is the key here...

Local and ambient RF, EM noises just don't have the affect on these rx's compared to fm, pcm, etc... SO FAR ANYWAY! :)

I fly indoors a lot at a shop in Dallas that has dirt and carpet track car/truck racing going on at the same time. 100+ rc'ers...

Sat. there were 85 car racers around while we where flying helis and NON of us Spektrum guys go ANY hits...

Love the Spektrum! :smokin:

I'll let ya know if I glitch it into the dirt! :)

[xStatiCa]

This thread is not talking about 'airwave RF noise'. It is about the fact there is 'local' noise generated ON the heli - and that is what 2.4g systems don't reject any different than any other RX.

But too many people seem to think the 2.4g means ALL noise has little or no effect. WRONG.

While I would not say ALL noise... it appears that most locally generated noise (like from the motor and ESC) are generated at a lower frequency and does not affect the RX.

Direct from spektrum website:

"Is it true that using Spektrum will prevent the problems I'm having with interference caused from electric motors and speed controllers in my model?

In many instances, yes it will. The radio interference caused by noisy motors, speed controllers, metal rubbing metal, noisy bearings, etc, generates all its interfering noise below 300MHz-right where we've been operating our 72 and 75mHz models. The Spektrum system operates at 2.4GHz, that's 2400mHz and is well above the frequency that model generated noise is on, so the Spektrum system is unaffected."

I personally keep things away regardless. Just my preference.

[xStatiCa]

The next person that has a major rebuild and has a 2.5ghz, PCM, and FM rx should take the ESC, motor, and rx out of the heli, tape them together, and do a range check at half throttle for testing each rx :).

[robmoney]

Just buy a spektrum and quit worrying! HAHA! :smokin:

Rob

[rdlohr]

Long term I will most likely end up with the spectrum technology, but I will still follow the best practices. My preference too.

[bmlasater]

fwiw..

I tried to make the original Spektrum 6Ch fail deliberately...I was never able to induce a "glitch" per se, but misplacement of other electronics, such as the gyro too close to the esc or motor will still allow emi issues to occur..Best practice still is to isolate any signal carrying wires or equipment as far from high current devices as practical...

John.

[rdlohr]

We talk a lot about this noise coming from the high current stuff but I've never seen anyone capture it.

I had a buddy at work measure the noise coming off the TREX600 BEC (there was none) today and he agreed to do some measurements on my heli in the next few weeks. You wouldn't belive how much noise was coming from a 60 hz fan, even when it was shut off!

I'm hoping to get some good traces with pictures. I'm hoping to resolve the age old question about where to place your ferrite ring.

Rick

[cbdane]

I've been seeing a few nice new birds that have this receiver in close proximity to either the ESC lines and/or the motor like this receiver is completely immune to noise and no longer requires isolation from high current, noise generating components such as the ESC and the motor.

The battery, ESC, and motor all have high current levels, upwards of 30 Amps running through them and they inherently create large magnetic fields that I feel should not be near any electronics that we are counting on to control our helis.

This just seems like bad practice to me and I'm afraid we are giving the newbies the wrong guidance here...

Here are some of the big differences in the spread spectrum system, as my meager understanding can decipher them:

- the control packets are sent at very high rates due to the very large bandwidth available at 2.5GHz; kHz packet rates, I believe instead of the 50Hz rate (50 per second) of FM systems. That means that many packets can be disrupted by noise without degrading control.

- each packet is digitally tagged with numerical checksums allowing the receiver to determine when data corruption has occured and to discard the bad information. Since the packets are coming so fast, no problem if one gets occasionally corrupted by a brushless ESC pulse and is thrown away since many more redundant packets containing the same information are being sent.

- Sources of electrical interference usually show up as noise at their primary frequency as well as sub-harmonics (components of lesser frequency). The 2.5GHz is so far above the spectral signature of noise sources (let's say the switching regulators in a brushless controller), that even sub-harmonics are out of reach, making it hard to disrupt.

The Spektrum system is certainly not immune to noise but it is huge improvement over our old 72MHz (~50MHz in the UK, I believe) systems.

Here's an interesting thing to think about. The control data packets are flying around fast and furious and the Spektrum receiver is correctly reading (and filtering) not just the intended signals, but those from every active transmitter! :shock: Sort of like, "Ahh, here's another data packet. Is it a good one? Let's verify the numerical checksum. Yep, it's okay. Now, was it intended for me? Nope, wrong ID tag. Oh well, wait for another one." A busy little receiver. Pretty amazing, really.

All this said, I'll keep my ESC well away from my Spektrum receivers, thank you very much! :)

[xStatiCa]

Here's an interesting thing to think about. The control data packets are flying around fast and furious and the Spektrum receiver is correctly reading (and filtering) not just the intended signals, but those from every active transmitter! :shock: Sort of like, "Ahh, here's another data packet. Is it a good one? Let's verify the numerical checksum. Yep, it's okay. Now, was it intended for me? Nope, wrong ID tag. Oh well, wait for another one." A busy little receiver. Pretty amazing, really.

Are you sure about that? If 2 frequencies are close to each other (side by side) you might get some very small signal from the other one but not enough that you transmitter is reading it's data. The RX actually locks onto 2 channels specifically... It does not listen to all of them or it would need 80 receivers... that would be quite a few antenna sticking out of that little receiver :).

Where did you read your info at?

[carlo_the_wonder_frog]

Even if the frequencies are close together, it still won't affect the spektrum as it does not have the ID tag, so any errant signals are tossed out. Yes it does see all the channels, but only listens to 2, and those packets sent on those channels must have the correct ID tags or it will not use them.

[MarkD]

I'm hoping to resolve the age old question about where to place your ferrite ring.

Rick

On the end of your ferrite finger? :mrgreen:

[Gary JP4]

Like Funky I too started out with a Trex 450 SE about a year ago with a JR 6102 with R610UL (I think) and the JR FM rx and had glitches and or cut outs. Specifically they were motor cut outs but not of the duration you get with a low battery. They lasted longer and had random durations. I reprogrammed pitch and power curves from what LHS had set for me, removed soft start, did the heatsink mod to the ESC, and still had cutouts. This scared me. I realy didn' t want to crash due to glitches. It seemed like a pretty big investment to loose for that reason.

I spectrumized my 6102 and glitches / motor cutouts stopped. A few months Later after a good crash from dumb thumbs I rearranged everything like yo are talking about here (battery front top, ESC front lower, RX behind motor, and Rdlohr's gyro mount). I also started cleaning up wiring.

But for what it is worth I have never had a cutout or glitches since going specturm regardless of layout. If I had it to do over again now I would get the DX7.

[Jermo]

I've been seeing a few nice new birds that have this receiver in close proximity to either the ESC lines and/or the motor like this receiver is completely immune to noise and no longer requires isolation from high current, noise generating components such as the ESC and the motor.

The battery, ESC, and motor all have high current levels, upwards of 30 Amps running through them and they inherently create large magnetic fields that I feel should not be near any electronics that we are counting on to control our helis.

This just seems like bad practice to me and I'm afraid we are giving the newbies the wrong guidance here...


I didn't read all the responses. The answer is NO. Nothing is 100% immune although DSS and DS2 are a good shot at not having issues. Recievers can be subject to an effect called "Front end overload". Basically there's an amplifier just after the antenna that gets overdriven by a STRONG signal (must be in the correct frequency range of the reciever OR a harmonic). This signal effectively makes the reciever Deaf.

The DX7 AR7000 reciever attempts to compensate for this by listening on 2 different frequencies and using 2 recievers located 90 degrees out of phase. For most applications the result is a bullet proof system, however, any strong signal close enough to the reciever(s) can still overload the reciever because: 1. they aren't shielded very well and 2. Proximity and signal width/strength.

Often if you experience interference that's wide enough and strong enough it's phase only affects ONE reciever.

Theoretically it should be rare to ever be completely locked out. I would guess flying in close proximity to a cell tower could potentially lock it out although better reciever shielding could potentially overcome that.
Jermo

Edit: to answer another part of the question: any strong EMF fields COULD potentially mess with the reciever. IF it could mess with it the result would be a total lockout or slow response. It's technically possible for signal to be induced on the servo wires to move something but the control system should detect that and compensate.
Jermo

[brovic777]

I've been using the DX7 for about 3 weeks on my Trex and have yet to experience any noise, glitches, etc, and I have the ESC right next to my reciever... At least yet...

[cbdane]

I've been using the DX7 for about 3 weeks on my Trex and have yet to experience any noise, glitches, etc, and I have the ESC right next to my reciever... At least yet...

Ah, the ****** litmus test. Issue settled. :mrgreen:

(just kidding with you Mr. 3Dz!)

[Finless]

My 2 cents.... While 2.4 is MUCH more immune I still would not let this allow a BAD wiring job etc. With the DX6 I would see guys that had no problems and some that the system just seemed SLOW... I am sure noise was casuing the RX to toss data away.

BUT there is another aspect. Noise up the signal wire from the RX to the servos or gyro. 2.4 wont help here! You still need to keep your outputs fromt he RX away from possible noise. Just last weekend I found a gyro having problems becasue of noise effecting it!

So while 2.4 is the future and will help eliminate shoot downs from other radios, noise on the 2.4 band etc... It doesnt make up for a BAD and noise INTERNAL system.

Bob