i for one will not use a pcm again, lost a heli once cause of it. all test's where carried out & also changed reciever once i got the heli back in the air, never had a problem again.

the old saying of once bitten twice shy still remains firmly in my head when ever i see a pcm reciever & will always shy away from them regardless of brand etc. only my thoughts & opinions though.

I'm not going to remove this thread.. There is a lot of good learning here. You just have to be paying attention and have an open mind to the facts and not carrying preconceived notions.

Guys,
no comments about my observations?

I think that test should be explained in detail, I feel it is very valuable.

For me, the above info on pcm versus PPM is good, and a well conducted test. But it doesn't do a lot for me, personally, as I wasn't shot down. In fact, I was the only guy flying at the time. I will say I got a bit cross when people say, it (PCM) doesn't stay in shut down. It does. PERIOD. I've experienced it, I've seen it in other people's CRASHED 'planes, and I've had many people tell me as well. I have also seen two lucky guy's who managed to fly through it and get control back. But I think the ratio is 2 saved and 11 crashed, plus my own two.
It does happen.
I also got a bit cross when simple things like batteries and switches are pointed to as the cause, when I clearly stated all was well. And in typical fashion "normal" fashion, plug it all in, as I explained a few (a lot) posts ago, and all worked. All the range tests worked.

But as sh says. Once bitten twice shy. For me twice bitten, so ....

But now I have been given "Another chance" with a replacement rx. I guess I'll try it, but I know for sure, in a crappy cheap arf it will never fail. Put it in a Patternship, and good 'ol Murphy will say hello.

MikeEast.
Maybe you can pick out the good learning bits and summarise. I'm don't seem to be able to see the good bits anymore.

Obviously it does not matter what anyone says, you have made up your mind and no one is going to change it. You are a smart guy and have read every word and have made your conclusion, so any comments I make are going to make no difference.

I will just go so far to say that I have never, ever seen or heard of anyone in person that has lost an airplane due to PCM lockout. Low voltage, failed switches and regulators I have seen. I hear a few people say they have lost a plane due to failsafe lockout, but I fly with and read about around 50 that do not for every 1 that has. Conversely I have personally witnessed countless planes on PPM go in due to mysterious interference of some sort. A PPM plane that gets 5+ seconds of interference is going in almost every time. Anything longer does not matter because the plane is in the dirt by then.

Now as far as lockout. Whether or not they will come out of lockout is not arguable. Its an electronic fact that when the signal is regained a PCM will and does unlock. However, it will remain locked out as long as the signal is lost. Thus the failsafe control inputs. IE,,, kill the engine.


Bottom line, its a preference and its a free country and both are good choices. Gather information, make your choice and go with it.

Not quite fair,
It does matter what other people say, otherwise I wouldn't ask. As for my mind being made up, well ....I can be swayed.

Back to it.
What I don't seem to be able to cope with, everybody says PCM will not stay locked out. Now I have definitely counted out the switch and low voltage. But how do we really know if the signal is lost?
In the case of PCM, to me, there seems no fair way of knowing if the signal is bad, for whatever reason, until it's over. Take my case. Total good ground test range, as per JR's document, which is the only way I know of , batteries good, etc. Plane takes off, goes quite away on the 270 degree turn around, yet went into fail safe, no more than 150 metres out, at approx 100 feet high. I even had time to turn away a little so the TX ariel was at a different angle.

Thanks to all for input

Now this is just talking and I am not claiming fact but I have seen 1 JR PCM go down but it was a strange crash.. The plane never went to failsafe settings it just held its last inputs and glided in at idle into the dirt. This was a single conversion PCM JR reciever on Ch14 or 16. The guy was flying a 40% Carden Cap... The failsafe was set to cut the engine and snap the plane into the ground or something, of which it did none. It just held its course at a low throttle setting and flew in a straight line right into the dirt at about a 30 degree angle.

At that time we discussed and I remember some talk about JR single conversion PCM receivers being more vulnerable than a Dual Conversion PCM. I wonder if that plays into your situation and if there is any truth to their being a difference between single and dual conversion PCM. So with that I will recant and say that I can truthfully say that I have never seen a Dual Conversion PCM receiver lockout or fail in any way. I cant even remember reading about a Futaba PCM locking out at all, I really cant.

Hi guys I have been following this thread with great intrest ,I have a couple larger planes 28%gassers ,nothing TOC but still several dollars in them and they both fly well .Both my sets are using PPM and we all know what a gasser with ign can do with RF ,so it took a little while to get things in order to rid myself of the dreaded RF and glitch probs .
I have read in here over and over that a PCM will come off of lockput if it gets a clean signal back ,Well thats the whole key IF ITS GETS A CLEAN SIGNAL BACK .Something is making it go into failsafe to start with and if its in the air chances are its not going away in 2-3 seconds of time and in most cases this is enough time to dirt nap most planes .Granted its better to have the failsafe set up to either idle or kill the engines ,but I feel either way that the plane is lost .
Im sure batterys, connectors, voltage regs and so on can and do contribute to this as much as noise in the air .
But what I am seeing here says that by using a PCM can and will save lives ,Sorry I'm having a little trouble with that one.
A plane hitting someone in the head even with a dead engine can and will do massive damage .Just because the engine is either dead or at a idle dosent mean the plane isnt going into the crowd ,just not as fast .
I box build my planes from kits and I would love to use a PCM to insure longer life & better signal and so on .But after watching a few go in, in total lockout I can't bring myself to do it .

Cyberwolf,
They were my comments implying that PCM may save a life or prevent serious injury. Clearly, you are correct that an idling/dead engine is very dangerous when out of control. I would make two points:
1. An engine running at speed will do more damage than one at idle. If you are going to be hit better that the prop is turning at 2,000 rather than 10,000.
2. An engine running at speed has a greater "zone of damage" because it will fly further and be going faster when it impacts the ground/person/property. Many airfields are close to roads or poputated areas, if the plane is set to idle is is likely to crash much earlier and therefore less likely to hit someone/something.

Are these events likely, no, but they do happen. The fact is that at least one person has been killed because PCM was not used (or not used correctly) - the child I mentioned earlier in the UK. Will it happen again? I pray not but I can tell you it will not be due to one of my planes flying away on me because my throttle cuts back to idle if I lose control. Bad things do happen but I think that using PCM makes it less likely that they will happen.

Changing tack slightly, there was a suggestions a few posts back that mentioned a new type of PPM Rx that allows PCM type features while operating on PPM. Maybe that's worht a look for people who are not comfortable with PCM.

Regardless of all of this it's good to have the debate, thanks for thall the inputs.

Sorry, but I don't think that's quite correct(unless there's been more than one)
The tragedy that I know about involved a model that did have pcm---but the throttle was set to "hold", not idle, and the impact was at full throttle.

Clearly PCM must be set to be worthwhile, I think my logic still holds true on this basis.

I haven’t seen it mentioned in this thread yet, but another big positive for PCM is low voltage flight pack detection. I don’t know if all systems offer the feature but the Futaba 9C PCM Super does. When the receiver detects a low voltage flight pack battery it retards the throttle. It can be overridden by bringing the TX throttle back to idle and then advancing the throttle for landing with power control. IMHO, if you fly valuable aircraft and are interested in safety PCM is the only way to go.

Can you use a futaba receiver with a JR transmitter?

Unless you can change the shift on the transmitter no they won't talk to each other.
Unless maybe theres something about the newer ones i'm not familar with.

Okay then,

My reasoning for PCM has always been grounded in my distinct ability to not pilot aircraft well. so any help I can give myself on comp day is welcomed, that includes glitch reduction ( a big problem in my electrics with PPM, I swapped them over to PCM after losing a CAP 10)

Can you run a dual conversion receiver with normal radio? Or do you need a dual conversion transmitter?

Pardon my ignorance but I am learning.

Hi Rendegade,
I'm using a JR 9XII Tx with both dual and single conversion PCM Rx's.
My understanding (correct me if I am wrong anyone) is that the only difference is the way Rx "interprets" the signal from your radio (dual conversion blocking out more unwanted evil signals ) hence you can just use your normal PCM capable Tx for Dual Conversion Rx.
All the best, Twoturnspin

Thanks mate

In support of ozzieflier, or at least sharing similar experiences, I too had what is referred to as lock-out two weeks ago. The 1/4 scale was no more than 200 feet away in clear sight when the engine went to idle and the plane flew for about 400 yards in a right bank and shredded through some trees. I had absolutely zero control. I moved the sticks every way without any resulting evidence of my influence from the ground. It was an eternity by the time the bits and pieces came to rest. The worst part....wasn't even my plane. A friend wanted me to fly it to trouble shoot some issues. I have been reading tons on the PCM issue and found some interesting things that I will share with you guys.
go to this web page...

http://www.torreypinesgulls.org/radios.htm

Thanks that was very interesting reading

Just wondering if anyone has any experience with the Multiplex Synth IDP receivers?

http://www.multiplexusa.com/product_fs.htm
http://www.multiplexusa.com/Support/...H%20Manual.pdf

These will apparently work with JR (and all +ve shift systems, but not Futaba from what I can gather).

Thanks.

I don't like that much IPD design.

From what the specs say, it is essentially a PPM system with some logic to filter out interferences. So the servo position is encoded with an ANALOG modulation.

PCM on the opposite is a DIGITAL modulation, which offer far superior signal robustness: it is very hard to corrupt the signal, and if that ever happens the receiver can know it thanks to a checksum attached to each frame - to me, the two are not even comparable!

Hello Guys,

I've read this whole part, before posting anything.
Let me tell this : PCM NO THANKS !!!!

PCM is actually the same signal, but with a digital code put on. If the RX 'sees' a bit wrong, it knows it did a bad reception.

At my club, everyone fly's PCM, except me.
Now, at a certain place, there is a small forest, and all the pcm guys seem to loose control if they accidently forget it, but it doesn't always happen.
I passed the same place, right after one crash happened there, nothing happened. Airplane ? Curare .40 with an 25 year old Sanwa, 40Mhz at AM.
Now, what do I notice ? If I do a groundcheck I get at least 2.5 the range of the so high priced Futaba's.
Now, I still use my OLD Multiplex receivers that are ppm single conversion ? What do I notice ? totally no problems, and way bigger range that the PCM guys. With groundcheck and in the air.
I can easily park my plane in the clouds, and go wide away.

Now, what happens usually with PCM ? It 'cleans' the signal, thus working away any distorsion, where you could notice a slighty later response. If this happens if you are flying away, you won't notice going out of reach, while with PPM, you will be noticing this with your airplane doing odd things, while still having the chance to turn it back towards you.

PCM so safe ? This summer in Chechia two people died after an airplane in F3A crashed in the public. The rx was programmed as it should be, yet, it quiet didn't do what it should do. The airplane was getting out of a hoover, while it leveled, and just flew away, right into the public, that was more then 200 meter away.
The pilot, yet a very experienced flyer was arrested, while he previously flew, and nothing happened.
Now, what did happen ? right at his freq. a very powerfull Tx started to send signals ( some radio ). Clearly, the PCM 'recognised' it, putting everything level, and there it went..........

Ofcourse, he got cleared from any blame !


Back to Belgium : You have to know it's really a small country, full with TX's, cellphones, radios that bring quiet a disturbance in the air. Now even the market opened to 35Mhz toys.
Still my PPM's function greatly, being single conversion.

What's happening more ? well, ACT braught out a dual frequency system, bringing the range up to 5 km, this setup and range was tested by TUV, and showed in a big 4 or 6 turbines model airliner.
They even have DSP on ppm, and their receivers are great. But I think I have to say they only have products in 35 and 40Mhz
Check www.acteurope.de . With ACT, you can litterally check how much distorsion and failure your TX saw. Really nice stuff. I just baught my first ACT DSP ( dual conversion ) With some of the models, you even buy a RX that is able to distribute 15A , and some models can directly work on 2C lipo, they stock servo's for these as well, capable of 39Kg/cm Patternflyers this is for you guys !

I hear Berg is going that way too. And towards my feelings, never buy PCM

For what it's worth the Multiplex IPD's are [sm=thumbs_up.gif]
As I recollect well, you can LOCK them at one frequency, thus getting rid from the probs of switching over to the frequency of your neigbour.
The IPD does bring DSP on PPM as well.
Same goes for the module for your transceiver. You dial in the frequency you want them to be on.