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PCM?

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Old 10-11-2003, 09:18 PM
  #1  
Steff
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Default PCM?

I will buy a new radio very soon and thought about a PCM radio.
The sales person in the shop where I buy all my supplies told me, that he does not fly PCM because it takes very long for the receiver to recover after a failure.

That puzzles me. He sure has no reason to sell me cheaper radio and he always advised me very well.

Should I save the money and buy a FM or do what the advertisement says and go with PCM?

Who has "neutral" advise?

TX

Steff
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Old 10-12-2003, 12:07 AM
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Default RE: PCM?

Haven't heard that one before. One guy I talked to said that he'd rather use PPM and "fly through" the interferance rather then have a failsafe kick in.
Another guy I talked to said he did a range check using his PCM radio and got tired of walking before he lost the signal.
I plan to switch to PCM soon on my large scale models.

Technically, PCM is FM. Both PCM and PPM (also PWM) broadcast of a Frequency Modulation. PCM is digital and PPM/PWM is analog. Food for thought
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Old 10-12-2003, 09:56 AM
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Default RE: PCM?

I use both with my 9C and the recovery time on the PCM is like milliseconds. Very fast. What may be deceiving is PCM will stay in failsafe as long as the interfearance persists As for which is best that is a tough one. Lots of opinions supporting both. Do a search, lots of threads on it.
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Old 10-12-2003, 01:12 PM
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Default RE: PCM?

ORIGINAL: 3DFanatic
Another guy I talked to said he did a range check using his PCM radio and got tired of walking before he lost the signal.
I recently got my first PCM radio and this was my experience too. I finally gave up trying to lose the signal during a range check... I have mine programmed to put the engine to idle when it goes into fail safe. At the smallest hint of interference it warns me by going to idle -- I think this is a good thing...
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Old 10-12-2003, 01:52 PM
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I have been flying PPM for most of my time. I once had my transmitter battery become disconnected and the plane tried to take off. I now fly only PCM in larger planes. I would recommend PCM because it will go to a predetermined position and if the noise is bad enough to keep you locked out for an extended period of time, the the PPM effect is a plane that you think you are controlling. I have not had a glitch with PCM, I don't have nervous servos, and I do have a definate pass/fail on my range check! TO me PCM is the choice for larger planes.
ORIGINAL: Steff

I will buy a new radio very soon and thought about a PCM radio.
The sales person in the shop where I buy all my supplies told me, that he does not fly PCM because it takes very long for the receiver to recover after a failure.

That puzzles me. He sure has no reason to sell me cheaper radio and he always advised me very well.

Should I save the money and buy a FM or do what the advertisement says and go with PCM?

Who has "neutral" advise?

TX

Steff
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Old 10-13-2003, 08:20 PM
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Default RE: PCM?

Per Futaba, the recovery from an interference event is on the order of 20-50 milliseconds. Damn fast. For example, suppose the signal is lost for 250 milliseconds, or 1/4 second. The pilot will not have control for 1/4 second, plus another 20-50 milliseconds, or a total of about 300 milliseconds. Basically, not much more than a 1/4 of a second. You won't be able to measure the lag time without a scope attached, and it would be invisible to the pilot. The recovery time on JR is roughly the same.

You can advise the person in the shop that he was incorrect, and have them check with Futaba for verification.
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Old 10-13-2003, 08:37 PM
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Default RE: PCM?

ORIGINAL: sfaust

Per Futaba, the recovery from an interference event is on the order of 20-50 milliseconds. Damn fast. For example, suppose the signal is lost for 250 milliseconds, or 1/4 second. The pilot will not have control for 1/4 second, plus another 20-50 milliseconds, or a total of about 300 milliseconds. Basically, not much more than a 1/4 of a second. You won't be able to measure the lag time without a scope attached, and it would be invisible to the pilot. The recovery time on JR is roughly the same.

You can advise the person in the shop that he was incorrect, and have them check with Futaba for verification.
This is all true except in reality the loss of signal, and the recovery, if any, is observed over many iterative periods of approximately 1/2 second, and results in a jerky motion of the airplane to control signal input.

There are some here that claim that PCM is more noise immune than PPM, such as a user MGLAVIN, but I've yet to see him offer up any proof of such an notion.

At one time a technician that repairs R/C equipment, his name escapes me now, but he wrote for RC Report magazine and wrote an article that intimated that from his observation it appeared that PCM seemed to "reach down into the mud" and pull out bad signals.

This is (false) basis of proof for proponents that want to argue this issue incessantly on the internet.

This of course was just an observation, and a conclusion made without formal measurement(s) performed in a controlled environment. It was simply a casual remark made by a bench technician turned RC magazine writer.

The fact is, at this time, nobody's offered up a coherent argument one way or the other.
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Old 10-14-2003, 02:07 AM
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Default RE: PCM?

ORIGINAL: jvolkes

This is all true except in reality the loss of signal, and the recovery, if any, is observed over many iterative periods of approximately 1/2 second, and results in a jerky motion of the airplane to control signal input.
It all depends on the interference. If its one hit, its just one hit, and the pilot many never even know he was hit. If its many hits, it would indeed appear jerky or slow to respond depending on the duration of the hits. Regardless if one hit or many hits, the recovery time is the same. As soon as the first good frame is received, it is reacted upon, and there is no other delay. A frame is 22.5ms in length, so the total recovery time should be well under 50ms for each interference hit.

There are some here that claim that PCM is more noise immune than PPM, such as a user MGLAVIN, but I've yet to see him offer up any proof of such an notion.

At one time a technician that repairs R/C equipment, his name escapes me now, but he wrote for RC Report magazine and wrote an article that intimated that from his observation it appeared that PCM seemed to !QUOT!reach down into the mud!QUOT! and pull out bad signals.

This is (false) basis of proof for proponents that want to argue this issue incessantly on the internet.

This of course was just an observation, and a conclusion made without formal measurement(s) performed in a controlled environment. It was simply a casual remark made by a bench technician turned RC magazine writer.

The fact is, at this time, nobody's offered up a coherent argument one way or the other.
I have read more than one technical explanation on the reasons why PCM will retain a good signal longer than a PPM receiver. I believe that most of it was related to better front end processing and signal to noise ratios, than having to do with PCM vs PPM specifically. However, I don't have enough knowledge in radio technology to explain it, nor is my memory fully intact in regard to those bits of information

Here is some additional info. Its mostly technical details on PCM. I couldn't find the exact references regarding the increase in signal quality that I read in the past, as I didn't keep the links.

http://www.aerodesign.de/peter/2000/...ml#Anker145432
http://www.elec.mq.edu.au/~cl/files_...1/lect_pcm.pdf
http://www.mh.ttu.ee/risto/rc/electr...dio/signal.htm
http://www.futaba-rc.com/faq/faq-pcm1024.html
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Old 10-14-2003, 07:27 AM
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Default RE: PCM?

Um, I don't want to get into another PPM vs. PCM war, but I do agree with jvolkes. As an engineer myself, I read most of your references, and then some as I'm a well versed veteran of these wars myself.

There's nobody that's done any testing. Most of the scenarios, and the proofs offered up to substantiate the claims made by these guys are hypothetical, relating to hypothetical reciever front ends, hypothetical signal voltage reference levels and hypothetical signal to noise ratios relating to the aforementioned signal reference levels. Additionally add a mix of lofty "assumptions" thrown in, and you've got nothing more than a very entertaining explanation of how things "could" work.

And so the arguments go on and on.......

When, and if, someone does some actual testing I'll tune in. Having said that, not only does one need to do some actual measurements, but one also needs to establish what one considers 'loss of control' for that's the only real quantifyable measure of the quality of the system.
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Old 10-14-2003, 08:33 AM
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Default RE: PCM?

I'm no engineer, but I'll tell you this....recovery is (nearly) instantaneous. i've heard this myth about pcm taking a long time to recover and I thought I'd find out once and for all.

I turned on my transmitter and model (w/PCM rx). I moved surfaces to one extreme. I then turned on second transmitter (PPM). Surfaces moved to fail-safe (now that happens after a moment of delay...but that's a design feature). Now, the moment I turned off the second transmitter, the surfaces snapped to whereever I had the sticks now positioned on the first transmitter.

I'm a firm believer in PCM. yes it is "so good" that it can mask a problem...but I'll take that "disadvantage".


for those who say: "they'll just fly through the interference with PPM" ..... I think they are really kidding themselves....


David Soniat - Tampa, FL
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Old 10-14-2003, 08:39 AM
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Default RE: PCM?

I would also like to see some substantive testing or references regarding this, as my memory could be of some of the references that you suggest. For the most part, I look at PCM and PPM as the same, with the main advantage that PCM has over PPM being the failsafe feature. I fly both PPM and PCM in my giant airplanes, and don't feel that either is slighted in any sense. I just feel naked with the PPM receivers knowing that if it goes into the pits, it could be turning a 32x10 propeller at 6,100rpm!!! Yikes. I would feel just as comfortable with a PPM receiver with a failsafe device on the throttle.

As far as range, signal quality, etc, my feeling is that they both serve us will, and provide a usable range far beyond our sight limits. A good quality PPM receiver is just as good as a good quality PCM receiver.

I fly both, so I can neither be right, nor wrong Hows that for political correctness
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Old 10-14-2003, 08:45 AM
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Default RE: PCM?

ORIGINAL: Buzzard Dave

I'm no engineer, but I'll tell you this....recovery is (nearly) instantaneous. i've heard this myth about pcm taking a long time to recover and I thought I'd find out once and for all.
Straight from Futaba, they have confirmed it is instantaneous, and the very first valid frame is acted upon without any delay. I think that puts receovery at less than 45ms. I consider that to be instantaneous in my book.
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Old 10-14-2003, 11:04 AM
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Default RE: PCM?

RE: PCM? (in reply to sfaust) Contact Moderator | | Revisions: 1 (Post No. 9)




Um, I don't want to get into another PPM vs. PCM war, but I do agree with jvolkes. As an engineer myself, I read most of your references, and then some as I'm a well versed veteran of these wars myself.

There's nobody that's done any testing. Most of the scenarios, and the proofs offered up to substantiate the claims made by these guys are hypothetical, relating to hypothetical reciever front ends, hypothetical signal voltage reference levels and hypothetical signal to noise ratios relating to the aforementioned signal reference levels. Additionally add a mix of lofty "assumptions" thrown in, and you've got nothing more than a very entertaining explanation of how things "could" work.

And so the arguments go on and on.......

When, and if, someone does some actual testing I'll tune in. Having said that, not only does one need to do some actual measurements, but one also needs to establish what one considers 'loss of control' for that's the only real quantifyable measure of the quality of the system.


< Message edited by branded -- 10/14/2003 7:35:27 AM >
\
As a former test engineer I would like to whip this dead horse a bit.
Testing is subject to many variables that can affect the results. They must be closely controlled to get meaningfull results. The only ones that that have the time for these are probably the people that make the equipment. Then you probably won't believe them.
The former RC writer that jvolkes quotes may be only a test bench technician, but he has many years of experience (tests). If you believe in unbiased tests I would go to him first. They may not be controlled tests but I think the quantity of them makes up for it.
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Old 10-15-2003, 12:26 AM
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Default RE: PCM?

There are some here that claim that PCM is more noise immune than PPM, such as a user MGLAVIN, but I've yet to see him offer up any proof of such an notion.
Wheres the proof for your beliefs or assertions? I have not seen any offered either.

This is old news... If the simple explanation I provided previously as to why there is a difference in noise immunity is not sufficent enough to realize it's plausible, I will offer empirical lab testing data. In fact we'll perform these tests with some of the equipment I am currently using, as the data I have is around five years old or better.

There are five common interference sources associated with RC receivers when using fifty channels spaced at 20 KHz: Single/Dual conversion, PPM/PCM RX's.

1) Single conversion RX's rejection frequencies at 460KHz apart. The 455 KHz 2IM syndrome.
2) Rejection of 3IM syndrome.
3) Adjacent channel rejection to TX side band splatter.
4) Image level response in and out of the RC frequency band.
5) On channel capture point between two signals at the RX.

Minimum guideline levels for Narrow Band Rx's will be created (based upon actual field data) and a standardized graph will be formed. This graph will chart the recorded readings as derived from each piece of equipment under test (EUT) with lab equipmet.

More to come[>:]
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Old 10-15-2003, 12:56 AM
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There's nobody that's done any testing. Most of the scenarios, and the proofs offered up to substantiate the claims made by these guys are hypothetical, relating to hypothetical reciever front ends, hypothetical signal voltage reference levels and hypothetical signal to noise ratios relating to the aforementioned signal reference levels. Additionally add a mix of lofty "assumptions" thrown in, and you've got nothing more than a very entertaining explanation of how things "could" work.

And so the arguments go on and on.......

When, and if, someone does some actual testing I'll tune in. Having said that, not only does one need to do some actual measurements, but one also needs to establish what one considers 'loss of control' for that's the only real quantifyable measure of the quality of the system.
NOT so, these tests exist. I have seen data. Those in the industry KNOW these findings to be factual. It's interesting how often the word hypothetical is used in your response. It is possible that you are simply ill informed and have yet to fully understand what you require to execute an educated and dutiful understanding.

"loss of control" or interference is established at a dB level to cause +/- 40 us servo jitter. Zero reference is based on -50 dBm input power to the RX's antenna.

Originally a plan was set up to find out what the real world conditions an RC RX operates under. What the RX see's in the received signal between the TX and RX is known as dBloss (dBl). Initial readings were calculated and subsequently substantiated with field tests and measurements utilizing an RC TX and simulated RX affixed to a helium filled balloon.
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Old 10-15-2003, 07:42 AM
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ORIGINAL: mglavin

There's nobody that's done any testing. Most of the scenarios, and the proofs offered up to substantiate the claims made by these guys are hypothetical, relating to hypothetical reciever front ends, hypothetical signal voltage reference levels and hypothetical signal to noise ratios relating to the aforementioned signal reference levels. Additionally add a mix of lofty "assumptions" thrown in, and you've got nothing more than a very entertaining explanation of how things "could" work.

And so the arguments go on and on.......

When, and if, someone does some actual testing I'll tune in. Having said that, not only does one need to do some actual measurements, but one also needs to establish what one considers 'loss of control' for that's the only real quantifyable measure of the quality of the system.
NOT so, these tests exist. I have seen data. Those in the industry KNOW these findings to be factual. It's interesting how often the word hypothetical is used in your response. It is possible that you are simply ill informed and have yet to fully understand what you require to execute an educated and dutiful understanding.

"loss of control" or interference is established at a dB level to cause +/- 40 us servo jitter. Zero reference is based on -50 dBm input power to the RX's antenna.

Originally a plan was set up to find out what the real world conditions an RC RX operates under. What the RX see's in the received signal between the TX and RX is known as dBloss (dBl). Initial readings were calculated and subsequently substantiated with field tests and measurements utilizing an RC TX and simulated RX affixed to a helium filled balloon.
Mglavin. What does single conversion vs. dual conversion have to do with Pulse Position Modulation (analog) vs. Pulse Code Modulation?

All the information you just provided is correct for rejecting unwanted rf signals near, or at the center frequency as a result of mixing (harmonics). All this is fine and dandy when one needs to consider rf sources such as cranes, other hobby transmitters, etc.

These sources however are not the root of our problems. The source most likely to interfere with our models almost always eminates from within the model itself. The source is noise, of a very high level in close proximity to the reciever.

The most common source is either conducted emi (transients, loose connections, bad servos, or poor radio installation, inadequate wire gauge, etc.) or radiated emi.

Radiated is far more likely to come from within the aircraft itself than anywhere else.
Metal to metal abrasion is one such source.
Whoops, I forgot to mention radiated ignition noise.........
Either of these two sources interferes with both types of recievers. The attributes you describe previously, 3IMG, etc. are shared attributes between both PPM and PCM recievers, and frankly I'm not sure what you're point is bringing that up.

You're confusing matters. Why bring up image rejection, and the like? What's that have to do with anything?

Ill informed, perhaps. I've yet to see any published hard facts. All I've seen thus far are assertions by you, and your ilk.

Now lest you believe that I'm arguing in favor of one scheme over the other, let me state that I'm not. I simply haven't seen anything to sway me one way or the other.

As for the aforementioned tests. You neglect to say who/whom conducted these tests, and for what puposes. Were they range testing for loss of signal, or did they have defined signal sources of interference by which they could establish the thresholds whereby 'loss' of signal occurs?
All this kind of "internet" information makes me skeptical.
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Old 10-15-2003, 08:12 AM
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Default RE: PCM?

I see some of you guys touting the advantages of failsafe.
I prefer PCM because of it's superior (at least in my mind ) error rejection
but the failsafe feature really confuses me. How do you set it ?. I have the engine set to kill but have never figured out where to set controls so I just leave them in the normal postion. Is there a better way to set the failsafe controls ?
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Old 10-15-2003, 08:52 AM
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Better?

Best I can do is tell you my settings and reason for setting them.

IMHO, fail-safe is not designed to save the aircraft, it's designed to prevent injury due to fly-aways. ... If I've lost control of it long enough for fail-safe to kick in, it's likely I'm not dealing with a small intermittent interference. Also, since the engine is a large cause (directly and indirectly through vibration) of interference, killing the engine may give me back control to land safely.

In all cases I set my throttle to kill the engine.
If I've lost control of my aircraft, I want it on the ground with in the flying area before it can make it behind the flightline.

Fixed wing:
sticks to the corner
This results in a snap/spin that will have the plane on the ground with least area travelled and is the only position that will guarantee a relatively small force imparted to the point of impact. It's also a fairly predictable flightpath enabling anyone in it's way to determine where to move to safety. Recovery is a familiar maneuvre. Intermittent Hits are very noticeable.

Heli:
hold all surfaces.
After meuch debate, I eventually conceded this is the setting most likely to reduce headspeed, thereby reducing likelihood of injury to high blade inertia. Flightpath is again predictable and ground covered likely to be minimal while recovery (auto-rotation) is easy (given height to recover headspeed) due to continued predictable flightpath reducing likelyhood of disorientation.

HTH, Jim.
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Old 10-15-2003, 11:01 AM
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Default RE: PCM?

It is set differently depending on your transmitter brand. It should be in the manual. I know its covered very well in the JR 10x and Futaba 8U and 9Z radios. Not sure about the others.

Which radio do you have?
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Old 10-15-2003, 05:39 PM
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Ermmm Corret if I am wrong BUT both PPM and PCM are digital signals. Where does the analogue factor come into it ?

PPM as he name implies is Pulse Position NOT Pulse Amplitude ( aka PAM ). The Pulse position varies in accordance to the stick movement ( in its most basic term )

PCM being Pulse Code is where the intelligence is carried within the coding of the PCM signal. With the JR it can be either 9 Bit ( ZPCM ) or 10Bit (SPCM ) thus giving either 512 or 1024 levels. This also why PCM can have inbuilt Failsafe as the decoding is carried out by a dedicated processor with inbuilt memory. The JR ZPCM can have different response delays of 0.3, 0.5 or 1 second before FS operates or just left on Hold. Cant remember what the SPCM delay is.

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Old 10-15-2003, 06:25 PM
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Default RE: PCM?

sfaust
It's a 9C. The problem is not how to set them but where to set them. Obviously kill the engine is a good plan, but the rest all seem to depend on what position you are in when the error hits.
Sticks to the corners might be the way to go.
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Old 10-15-2003, 07:05 PM
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Default RE: PCM?

Ermmm Corret if I am wrong BUT both PPM and PCM are digital signals. Where does the analogue factor come into it ?

PPM as he name implies is Pulse Position NOT Pulse Amplitude ( aka PAM ). The Pulse position varies in accordance to the stick movement ( in its most basic term )

PCM being Pulse Code is where the intelligence is carried within the coding of the PCM signal. With the JR it can be either 9 Bit ( ZPCM ) or 10Bit (SPCM ) thus giving either 512 or 1024 levels. This also why PCM can have inbuilt Failsafe as the decoding is carried out by a dedicated processor with inbuilt memory. The JR ZPCM can have different response delays of 0.3, 0.5 or 1 second before FS operates or just left on Hold. Cant remember what the SPCM delay is.
PPM is said to be the analog of the transmitter stick position. The mechanism by which the pulse width, of a given pulse in a Pulse Position scheme, is varied is by use of analog integration over time.

Yes it is a digital signal whose pulse width is the analog of the transmitter stick position for a given channel.
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Old 10-15-2003, 07:57 PM
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Default RE: PCM?

Ah, I understand. A hotly debated topic.

I set the throttle to kill or idle. I feel this one is essential for the safety reasons. If you get interference, and it recovers, most pilots can land dead stick. Yea, sometimes it happens at a bad time, but its still better than your plane taking off to the pits and mowing down some spectators. I also set failsafe to turn off any extraneous items such as a smoke pump, lights, and so on. These could also be a source of interference, and if shut down it might just eliminate the problem altogether.

For the control surface, I like the sticks to the upper right corners. Like the statement earlier, the 'sticks to the corner' is designed to sacrifice the airplane yet attempt to protect the people on the ground. I can't think of any other position that will dissipate the energy of the airplane any better than killing the engine and commanding hard snap roll. If you are flying at an event and all the proper AMA safety rules are followed, the kill/snap configuration will almost always leave the airplane on the right side of the flight line and out of the pits. If left at hold, who knows where the airplane would end up. It could be the next county!

Others would recommend leaving the controls to either neutral or at the last commanded position (basically hold mode). However, a plane in hold mode, even with the engine dead can still cover lots of ground, and might make its way into the pits or local property. But, if they fly from a sparsely populated area with no spectators, last or hold might work best for them, and I might do the same under those conditions. I wouldn't do this in populated areas, or at events or fields where there is lots of spectators, traffic, buildings, etc
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Old 10-15-2003, 09:30 PM
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Default RE: PCM?

If its a question of failsafe programing, PCM is not alone Look at the Multiplex IPD receivers, Multiplex which is the one that introduced PCM to radio control, has now stopped making them altogether in favor of the IPD receivers .. Evolution
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Old 10-15-2003, 11:00 PM
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For the record, I am not an Engineer or involved in this industry. I have done lots of research on this subject. I compile data and regurgitate my understanding in my responses. I have several sources close to the industry that I rely on for technical information and understanding.


Mglavin. What does single conversion vs. dual conversion have to do with Pulse Position Modulation (analog) vs. Pulse Code Modulation?
Nothing. I was simply noting that these were included in my ramblings.

All the information you just provided is correct for rejecting unwanted rf signals near, or at the center frequency as a result of mixing (harmonics). All this is fine and dandy when one needs to consider rf sources such as cranes, other hobby transmitters, etc.

These sources however are not the root of our problems. The source most likely to interfere with our models almost always eminates from within the model itself. The source is noise, of a very high level in close proximity to the reciever.
I’m not sure why you’re suggesting these problems are not the “root”, these scenarios exist and are problematic. How does one quantify “most likely”?

The most common source is either conducted emi (transients, loose connections, bad servos, or poor radio installation, inadequate wire gauge, etc.) or radiated emi.
This maybe true but I suspect it’s an assumption. A properly rigged and operating model will not have these attributes, albeit it’s a plausible occurrence and may also be a common scenario. RFI can and will present itself; I believe it’s more common than EMI in the day to day use of our models. Therefore the aforementioned information has merit. I’ll stick my head out and suggest this information is generic to the either RFI and or EMI.

Wouldn’t attempting to distinguish the difference between RFI and EMI be a rather lofty adventure? Isn’t noise, noise? Does an RC RX know the difference?

Radiated is far more likely to come from within the aircraft itself than anywhere else.
I concur.

Metal to metal abrasion is one such source.
Whoops, I forgot to mention radiated ignition noise.........
Either of these two sources interferes with both types of recievers.
Again, I concur.

The attributes you describe previously, 3IMG, etc. are shared attributes between both PPM and PCM recievers, and frankly I'm not sure what you're point is bringing that up.
3IM is most definitely a required and or wanted and shared attribute of either AM/FM PPM or PCM RX’s.

You're confusing matters. Why bring up image rejection, and the like? What's that have to do with anything?
What happens when two signals appropriately spaced enter the 1st mixer? The RX must be able to reject these two signals by a calculated factor higher than the received controlling channel. Two similar signals are injected during test’s, thus my reference.

Ill informed, perhaps. I've yet to see any published hard facts. All I've seen thus far are assertions by you, and your ilk.
My assertions are for discussion, it’s not my intention to be a condescending or lofty. I provide the reasoning for such and it’s up to the individual reading the information to determine one way or the other.

Now lest you believe that I'm arguing in favor of one scheme over the other, let me state that I'm not. I simply haven't seen anything to sway me one way or the other.
I hear where you’re coming from; based on your comments I assumed you were in favor of the PPM scheme.

As for the aforementioned tests. You neglect to say who/whom conducted these tests, and for what puposes. Were they range testing for loss of signal, or did they have defined signal sources of interference by which they could establish the thresholds whereby 'loss' of signal occurs? All this kind of "internet" information makes me skeptical.
The tests I am aware of were performed by several individuals and hobbyists in the industry.

Once values could be placed on what an RC model sees, tests of interference could be recorded simulating real world field conditions for evaluation purposes. Defined signal sources and thresholds were employed.

One could look at testing RC RX’s from several levels, BUT what really is the tell all is the control signal the servos actually see, If we can establish what dB level is required to cause servo jitter (+/- 40 us) we have a method that suggests which scheme is superior. Could it be any simpler?

Should have some new test data tomorrow afternoon. Were going to use Futaba RX's specifically and hopefully some JR equipment if I can round some up.
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