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Multiplex Evo and IPD technology?

Old 06-29-2005, 03:42 PM
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JLS
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Default Multiplex Evo and IPD technology?

I am considering buying a Evo 12. My problem is that I have been under the impression that PCM technology is better for large scale gas planes. I have read several posts regarding PCM vs PPM and understand the pros and cons of both but there is very little discussion regarding IPD technology. I would really like to be comfortable with IPD before I buy and put into my first giant gasser. Comp-Arf Extra 330.
Old 06-29-2005, 04:51 PM
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sillyness
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Default RE: Multiplex Evo and IPD technology?

I had an Evo 12... I sold it. Some features it was lacking that I wanted:
1. There is only one expo setting per surface per model. You can't change the expo with dual rates or flight modes.
2. There are no multi-point mixes... all of them are linear. I use multipoint for several things.

Other than that the radio was OK.

I still use the IPD RXs in my gas planes... I really like them. They get awesome range checks with my 10X... better than most other RX's I've used. Personally, I don't like PCM and will never use it again. I want to know I'm getting hit without my RX locking out. FWIW... I also use some plain old PPM RXs in a gas plane... they work great. You just have to set your plane up correctly to use them... you should really do that with PCM also... otherwise it just hides the problems until they big enough to bite you in the knickers.

I'm sure someone will disagree, but this is how I do things.
Old 06-29-2005, 11:42 PM
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JLS
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Default RE: Multiplex Evo and IPD technology?

Do you have a description of what IPD is? What is the theoretical advantage of IPD over PPM, or PCM for that matter? I am hoping someone can convince me that this technology is better or at least equal to PCM for gas planes. Since you mentioned multi-point mixes, can you give me an example of why you would use a mix like that. I'm curious if it is something that I might feel I need in the future. Thanks
Old 06-30-2005, 01:41 AM
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Default RE: Multiplex Evo and IPD technology?

Have look at this document:
http://www.mpx.speedkom.net/cms/vors...tip_ipd_gb.pdf
Old 07-01-2005, 02:04 AM
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Default RE: Multiplex Evo and IPD technology?

IPD is the replacement technology for PCM. Multiplex were first to introduce PCM, and now are the first to move on from PCM. IPD will work with any PPM transmitter, work at PPM speed (not slowing the servos like PCM does) whilst giving the interference rejection and failsafe qualities of PCM.
When PCM was introduced the only way of the Rx scruitising the incoming signal was first to give the signal a digital numeric value. Technology has moved on and modern processors can interrogate the signal in real time (hence the speed improvement). The algorithm can tell the difference betwwen a good signal frame and a bad one. Moreover, it can take various stages of action in the event of a poor signal, ranging from just waiting for the next frame up to full failsafe. However, in the event of a few bad frames, these can be "fixed" by the Rx storing the signal trend. This has the effect of slowing the servo response before the model gets to the point were the signal is so bad that failsafe cuts in, so you get some warning of the problems.
I hope this helps,

John
Old 07-03-2005, 09:30 PM
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Default RE: Multiplex Evo and IPD technology?

Thanks for the responses. I am much more comfortable investing in this radio. Before this thread, i was concerned that IPD was a marketing way of saying PPM. Here in the states, we are a little unfamiliar with Multiplex and I was not aware that they are on the "cutting edge" in regards to RC.
Old 07-04-2005, 11:22 AM
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Default RE: Multiplex Evo and IPD technology?


ORIGINAL: JohnMac

IPD is the replacement technology for PCM. Multiplex were first to introduce PCM, and now are the first to move on from PCM. IPD will work with any PPM transmitter, work at PPM speed (not slowing the servos like PCM does) whilst giving the interference rejection and failsafe qualities of PCM.
When PCM was introduced the only way of the Rx scruitising the incoming signal was first to give the signal a digital numeric value. Technology has moved on and modern processors can interrogate the signal in real time (hence the speed improvement). The algorithm can tell the difference betwwen a good signal frame and a bad one. Moreover, it can take various stages of action in the event of a poor signal, ranging from just waiting for the next frame up to full failsafe. However, in the event of a few bad frames, these can be "fixed" by the Rx storing the signal trend. This has the effect of slowing the servo response before the model gets to the point were the signal is so bad that failsafe cuts in, so you get some warning of the problems.
I hope this helps,

John
I have had a single conversion IPD receiver that I have used for several years with no problems.
However I think PCM is better because each word (pulse) contains its ID. That makes each pulse independent. Since interference is random in nature and not synchronized with the frame the next interference pulse is not likely to occur in the same PCM word. Thus the PCM receiver will continue to work after a receiver that depends on the integrety of the frame has quit working - especially those control pulses at the end of the frame.
If you get interference that is heavy enough to wipe out the PCM receiver the PPM (IPD) receiver will be long dead. If that's an advantage I don't see it.
Old 07-05-2005, 09:46 AM
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Default RE: Multiplex Evo and IPD technology?

Each PCM system is different but a typical protocol is to split the data into two packets - two packets of four channels rather than one frame of 8 channels as PPM does. However each PCM packet still has a header with lots of data to identify that packet and if that header gets blasted the packet is failsafed. On the face of it that seems better, if the interference is very very short lived then you lose 4 channels in that packet rather than 8 channels until the next PPM frame, but since PCM runs so slowly (apart from the new 14MZ), the actual time that control is lost until regained is pretty much similar to PPM. In reality you are going to struggle to notice the difference between IPD and PCM when interference strikes.
Old 07-05-2005, 10:46 AM
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Default RE: Multiplex Evo and IPD technology?


ORIGINAL: HarryC

Each PCM system is different but a typical protocol is to split the data into two packets - two packets of four channels rather than one frame of 8 channels as PPM does. However each PCM packet still has a header with lots of data to identify that packet and if that header gets blasted the packet is failsafed. On the face of it that seems better, if the interference is very very short lived then you lose 4 channels in that packet rather than 8 channels until the next PPM frame, but since PCM runs so slowly (apart from the new 14MZ), the actual time that control is lost until regained is pretty much similar to PPM. In reality you are going to struggle to notice the difference between IPD and PCM when interference strikes.
I normally use PPM simply because I have several of the PPM receivers but only one PCM receiver.
I recently had a severe interference that I never did isolate. I changed all components except the wiring. I could get about 100' with the engine off and only about 10' range with it running. I put in the PCM receiver and had 300' range with the engine running. I concluded that the PCM receiver is a hell of a lot better than the PPM receiver. Unfortunately I didn't think to try the IPD receiver

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