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HelicopterRadio - Servo - Gyro - Gov - Batt › Futaba 9CHP vz 9CHF
09-02-2003 09:10 AM  14 years agoPost 1
dragonhawk

rrNovice

Seoul, South Korea

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I am brand new to rc heli and am doing some reaearch on radios. I was wondering what the difference if any is between these two radios. Also is this a good radio for a beginner with high aspirations(sp?). I have read alot of the posts in the beginner section and they all seemed to point in the same direction of spend the money on the radio. Thanks for the help.

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09-02-2003 09:18 AM  14 years agoPost 2
mvhf

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Antwerp, Belgium

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The difference is Either FM(PPM) or PCM.
So it is dependeing on the module which is in the back of the TX.
So get the CHP, PCM can do PPM too, while not the other way around

regards

Marc

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09-02-2003 09:31 AM  14 years agoPost 3
Angelos

rrKey Veteran

nr Oxford, OX11, UK

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mvhf,
sorry but I think you are wrong. The TX module is just a transmitter. It doesn't know and doesn't care what it transmits (PCM or PPM). Also all modern radios encode both PPM and PCM.

I am not sure what the last leter stands for but I suspect it shows what type or receiver is supplied together with the TX.

-Angelos

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09-02-2003 09:43 AM  14 years agoPost 4
KMorgan

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Bonnie Scotland

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I agree with Angelos

Keith

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09-02-2003 09:47 AM  14 years agoPost 5
mvhf

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Antwerp, Belgium

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Angelos, I meant the same thing, but I was not sure about the tx whether all tx could handle both, I know for sure the rx in the box is different

look here: futaba site

regards

Marc

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09-02-2003 01:21 PM  14 years agoPost 6
dragonhawk

rrNovice

Seoul, South Korea

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When I said that I was new to the world of rc helicopters i meant brand new. I do not know what you mean when you said PCM can do PPM too. What is PCM and PPM. I could understand it better if I knew what you were talking about. So which is the better radio? I am guessing the CHP. Thanks for the help.

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09-02-2003 01:33 PM  14 years agoPost 7
mvhf

rrApprentice

Antwerp, Belgium

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I'll try to do some small explanation on this.
You 'll find a lot of people who wants PPM instead of PCM and vice versa, so I'll not start a debate which one is better:

It's just the way how the transmitter is talking to the receiver. With PCM there is some code check so only valid (not transformed by radio noice) singals are handled. While with ppm every signal is processed by the receiver, which may cause some jitter, these are small movements of the servos.
If you do a search on PPM or PCM you'll find a lot of topics regarding this isue

regards

Marc

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09-02-2003 01:38 PM  14 years agoPost 8
Angelos

rrKey Veteran

nr Oxford, OX11, UK

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PPM is the older standard where the servo possitions are sent as a series of pulses. the pulse width defines the servo possition. interference may ocasionaly disturb the comunication and this affects the servo possitions. This is what happens when people say "i got a glitch".

PCM is a data encoding system. The radio sends data to the receiver. The receiver checks is the received data are valid and then update the servo possitions. Intererence may still be receied which will damage the data but the servos will not glitch as the receiver will reject bad data packets.

The advantage of the PPM is that you can have a feel of the comminication. You can see if are getting glitches before it is too late.

PCM will hide away all glitches but the problem may be there until it is too late. PCM on the other hand offers Failsafe. The failsafe will possition all your servos to predetermined possitions should the comunication be desrupted for one second. This can be engine to idle, rudder to newtral, etc.

Most people who fly helis use PCM. Both PPM and PCM are information encoding tequiques. The actual signal is FM (frequency modulated) in both cases.

Both TXs are the same and will both do PPM and PCM. The CHP most likely comes with a PCM receiver and the CHF with a PPM receiver.

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09-02-2003 01:42 PM  14 years agoPost 9
dragonhawk

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Seoul, South Korea

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It now makes sense. Thank you very much for the explanation.

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HelicopterRadio - Servo - Gyro - Gov - Batt › Futaba 9CHP vz 9CHF
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