Is the Spectrum receiver totally immune to noise?

[PeterV]

Yep ******, as mentioned it is a technical thing...and may not show up at all in practice.

Even if an ESC is well designed and has perfect shielding, it just so happens that there are three wires coming out of it, carrying INTENTIONAL HF wave forms, to control the motor! Carrying 20 to 30 amps of that waveform! So it is a reasonable powerhouse of potential radiating. (of that range in the 200KHz to 400KHz area - or whatever it exactly is)

BUT...you might very well wrap those three (or one) wire right around a RX and not even see a problem! Many factors come into it, so only a case by case result will show which Rxes and which ESC's/wires/layouts ever even matter.
Lucky? Unlucky?

Once again the bottom line remains that is is not a good idea to have those POTENTIAL problem situations at all. eg good component layout choices.

Have you tried putting a small piece of duct tape in between the RX and ESC (on the frame I guess) as shielding? Just in case.

[rdlohr]

On the end of your ferrite finger?

Sounds engaging...

[brovic777]

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

So Guys,
So, an ESC can have a static discharge that will jump through the wires and disrupt the electrical current flow going to the servos and gyro making glitches... hmmm

Isn't that like the governments super weapon called an "EMP" Electrical Magnetic Pulse" used to disrupt any electrical devise within a specific taget area, depending on the amount of EMP emitted to destroy enemy territories????

Oh and by the way, "Duct Tape" does not protect from EMP's... I wonder if the static platic that my computer parts come in can be used to protect from this...

[PeterV]

That weapon is more often used to knock out the electronics on model heli's....
oops..that was classified.

[rdlohr]

Static has nothing to do with it. The ESC wires create a magnetic field. The magnetic field causes current to flow in metalic objects nearby.

A transformer is exactly that. You put current through one winding, and it induces it into the other winding. Like magic.

Incredibly enough, it is like the EMP I think but on amuch smaller scale.

[rdlohr]

That weapon is more often used to knock out the electronics on model heli's....
oops..that was classified.

Careful, you may lose your clearance! :D

[cbdane]

So Guys,
So, an ESC can have a static discharge that will jump through the wires and disrupt the electrical current flow going to the servos and gyro making glitches... hmmm

Isn't that like the governments super weapon called an "EMP" Electrical Magnetic Pulse" used to disrupt any electrical devise within a specific taget area, depending on the amount of EMP emitted to destroy enemy territories????

Oh and by the way, "Duct Tape" does not protect from EMP's... I wonder if the static platic that my computer parts come in can be used to protect from this...

Better stick to theology. Your talent for taking a thread into the dump is endless... :?

[ZX11]

Internal and external noise is an interesting concept. I wasn't aware that the plastic Trex canopies divided the radio noise :wink: The 2.4G selectivity amp (or circuit) should ignore that noise internal or external since it is soooo far out of band.

I always took internal noise to be within the receiver affecting the downconverted signals. Aren't modern chips shielded?

[brovic777]

Better stick to theology. Your talent for taking a thread into the dump is endless... :?

Hey cddane, I'm trying to understand how heli's work as much as I can. Knowlege=power you know. I went through this learning curve back in 1999 when I started learning how to build computers.

Now I can build a computer from the ground up. All my friends would always come to me to get thier computers fixed, which I would do it for free by the way, instead of charging $90 diagnosis fee as many retailers such as Compusa and Best Buy do.

As I learn about heli's, I can do the same to help others later.

[cbdane]

Better stick to theology. Your talent for taking a thread into the dump is endless... :?

Hey cddane, I'm trying to understand how heli's work as much as I can. Knowlege=power you know. I went through this learning curve back in 1999 when I started learning how to build computers.

Now I can build a computer from the ground up. All my friends would always come to me to get thier computers fixed, which I would do it for free by the way, instead of charging $90 diagnosis fee as many retailers such as Compusa and Best Buy do.

As I learn about heli's, I can do the same to help others later.

Agreed. I was out of line.

However, I don't think you have the attitude/demeanor of a student looking to learn; rather more of a self-proclaimed expert who is so often dangerously wrong; for example your ESC installation, duct taped blades, and living room escapades. This is definitely not helpful to new forum pilots (like me) looking for advice.

Knowledge may equal power (your words) but around here, power isn't needed. Just helpful (and hopefully accurate) advice so we can all become better heli modelers. You just haven't fit that mold yet and, in my opinion, have quickly gone from a mildly entertaining distraction to a serious nuisance.

Just some humbly offered views.

[PeterV]

ZX11...if you have ANY freq, of enough power, it can couple into the circuitry of an electronic device. Not as the native RF...or as the IF Freq (downmixed)...but just as the freq it came as (whether 400KHz or 60Hz or anything). It gets onto the voltage rails...existing signal paths....'joining' them, riding on them. Thus the signal is no longer just what it was supposed to be.

In RC RX the carrier (72MHz or 2.4G) is downmixed to an IF freq..then the data decoded off it. Data to drive servos. Servos run off DC...but it is controlled DC levels.
So if there is noise ON the servo signal now - fed into the RX decoding along the way - you get servos with signals of the true commands, plus voltage variations of the noise. Could be High freq, low freq...any freq.
= servos now jitter, hum or buzz.

In other cases, noise could "swamp out" an area of the RX circuitry and then it can't pass any info at all. There are many variations, according the actual noise...where it got in...how strong it was to add to, or swamp out, existing signals....or what it exactly affected in the RX (or whatever electronic device it got into).

[brovic777]

You just haven't fit that mold yet and, in my opinion, have quickly gone from a mildly entertaining distraction to a serious nuisance.

Just some humbly offered views.

Dear cddane, sorry that you find me a nuisance. My advice to you that you simply ignore any post that I write or reply to. You have the power within your keyboard to skip a post or scroll down and not read anything that I write.

Helifreak.com is for "FUN, LEARNING, FRIENDSHIP AND MUTUAL RESPECT."

Guess you can't please all people at all times.

[spork]

This is definitely not helpful to new forum pilots (like me) looking for advice.

cbdane, you should come join the Group W Flying Club down here in Mtn View one day. We have PLENTY of advice (not necessarily good advice, but it's free - as is the abuse :mrgreen: ).

[kgfly]

Another opinion:

The Spektrum Rx is highly resistant to noise from all onboard sources and despite discussion of magnetic coupling, is highly unlikely to be affected by the ESC or motor. As pointed out, other downstream components like the servos and gyro are still susceptable to noise induced in the servo leads so good wiring practice is still necessary. I have seen examples of Spektrum Rx mounted on top of ESCs and operated without a problem, although I would not recommend that myself.

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! 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.

With respect, this is an incorrect understanding of how spread spectrum in general or the Spektrum in particular work.

In spread spectrum the signal is encoded with a unique key (in this case, the Tx/model ID). It is not an ID tag inside the packet that the Rx uses to recognise it, it is an encoding key which is applied to the packet to uniquely spread the information across many frequencies. An Rx will only see packets encoded with the ID it is programmed to use. All other transmissions in the band simply appear as noise. So the Rx cannot see or decode packets from any other Spektrum Tx or any other 2.4GHz source, it will only ever see packets from its bound Tx.

You are correct that each packet has a checksum and the Rx uses that to check that the packet is not corrupted before using its contents.

Also AFAIK the Spektrum system still only sends packets 50 times a second. The packets are sent at a high data rate so only last for milliseconds. This low duty-cycle transmission is what allows the Tx to use so much less power than a legacy FM Tx which transmits continuously. If noise levels on both channels for both Rx were to rise far enough for packets to get lost, then at some point you would notice a sluggish response and then if it got even worse, the Rx would go into failsafe until the noise level fell again. I have yet to see a single validated report of a Spektrum Rx going into failsafe as a result of interference.

[Finless]

However, I don't think you have the attitude/demeanor of a student looking to learn; rather more of a self-proclaimed expert who is so often dangerously wrong;


I am curious... Can you show me a post where he proclaimed himself an expert?
Dude... I know he can be annoying but remember Fun, LEARNING< and Mutual respect be it n00n or not!

kgfly

As pointed out, other downstream components like the servos and gyro are still susceptable to noise induced in the servo leads so good wiring practice is still necessary.


That is my point! A good setup will always yeld best performance... 2.4 may be better at noise but I do NOT believe it is immune! Noise from a bad setup may in fact cause latency (lost data) on a 2.4 system thus reducing performance! I have seen it on DX6 systems (or at least I believe that is why it was so damn slow compared to other setups).....

In the end I want to say... just becasue your on a DX6 or 7, DONT use that as an excuse to have a crappy setup!

Bob

[cbdane]

With respect, this is an incorrect understanding of how spread spectrum in general or the Spektrum in particular work.

In spread spectrum the signal is encoded with a unique key (in this case, the Tx/model ID). It is not an ID tag inside the packet that the Rx uses to recognise it, it is an encoding key which is applied to the packet to uniquely spread the information across many frequencies. An Rx will only see packets encoded with the ID it is programmed to use. All other transmissions in the band simply appear as noise. So the Rx cannot see or decode packets from any other Spektrum Tx or any other 2.4GHz source, it will only ever see packets from its bound Tx.

Yep, that's the way it's been explained to me. My incorrect reinterpretation is simply the result in the shortcoming of my ability to completely understand the keying process! :oops:

Also AFAIK the Spektrum system still only sends packets 50 times a second. The packets are sent at a high data rate so only last for milliseconds. This low duty-cycle transmission is what allows the Tx to use so much less power than a legacy FM Tx which transmits continuously.

On this topic, though, I'm still a bit uncertain since my understanding of a high transmission rate of redundant packets came from a conversation with Paul Beard, the designer, at a heli jamboree this year. However, I may have been a little slow on the uptake in this case also.

Thanks for the clarification!

[cbdane]

You just haven't fit that mold yet and, in my opinion, have quickly gone from a mildly entertaining distraction to a serious nuisance.

Just some humbly offered views.

Dear cddane, sorry that you find me a nuisance. My advice to you that you simply ignore any post that I write or reply to. You have the power within your keyboard to skip a post or scroll down and not read anything that I write.

Helifreak.com is for "FUN, LEARNING, FRIENDSHIP AND MUTUAL RESPECT."

Guess you can't please all people at all times.

You're right. My sincere apology to you (again :oops:) and to the rest of the forum. Been cooped up with the flu and spending way too much time hanging around here! :arggg: Time to fly some heli's!

I'll behave now. :glasses2:

[rdlohr]

Wow, this thread took a turn for the worse. Cbdane, hope you feel better. ******, you are welcome to be a nut, just be safe!

Rick

[kgfly]

Also AFAIK the Spektrum system still only sends packets 50 times a second. The packets are sent at a high data rate so only last for milliseconds. This low duty-cycle transmission is what allows the Tx to use so much less power than a legacy FM Tx which transmits continuously.

On this topic, though, I'm still a bit uncertain since my understanding of a high transmission rate of redundant packets came from a conversation with Paul Beard, the designer, at a heli jamboree this year. However, I may have been a little slow on the uptake in this case also.

Well I would definitely take Paul Beard's input over mine !

[spork]

I am curious... Can you show me a post where he proclaimed himself an expert?

He talks about his whoopin' 3DZ and his super-human bionic reflexes in several posts. I think he's just funnin' with us, and I think most people think that as well; but if you take him literally it would be easy to get the idea that he's a bit full of himself. But frankly, I'm not going to mess with him - did you see those HUGE gunz? :mrgreen:

[spork]

Well I would definitely take Paul Beard's input over mine !

Kenneth, I assume the key you're talking about is the spreading code - yes? Is the Spektrum a direct-sequence or frequency-hopper?

[xStatiCa]

DX6 and DX7 are Direct Sequence.

[kgfly]

Yes and DSSS.

Apparently Nomadio (Futaba FASST) is FHSS but Spektrum and XPS/XL are DSSS.

XPS/XL is clever in that it only uses a single (bidirectional) channel for the link but if either the Tx or Rx detects too much noise (too many lost packets) they will initiate a jump to another channel. This doesn't qualify as FHSS since it is only on an as-needed basis and typically would not happen at all.

[skripo]

Is it possible that the position of the board between ythe RX and TX blocked the signal?

The presence of another 2.4 GHZ signal is not the death knell for the DX, look how many devices can get along on the same frequency. My router and cordless are just one example.

[Jermo]

Mongo, Just as a test perhaps try encasing the RX in a conductive material and attaching it to the aircraft ground. Sounds like it could be front end overload or signal injection. If it's front overload there's not much to be done. Basically the scoreboard 2.4GHz signal is so loud the RX can't hear anything else. If it's injection type interference then shielding the RX should help. Based on the description of the model "glitching" it sounds more like injection interference.
Jermo