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Question about Radio's

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Old 07-13-2005, 12:46 AM
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Hellbringer
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Default Question about Radio's

hi i am looking to get a new radio and i am looking at the Futaba 9CAPS or the Futaba 9CAFS . The frist question i have is what is the difference between PCM and FM? What are the advatages and disadvantages? Also i have heard about PCM lock out (from my understanding it locks you out so you cant control your plane) dose this happen offten and what is this? Thanks Mike
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Old 07-13-2005, 07:26 AM
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Default RE: Question about Radio's

First off understand that the transmitter is the same and will transmit both PPM (fm) and PCM. The model designation only refers to the reciever that ships with the package and this reciever accounts for the price difference as well.

Both are transmitted on an FM signal, its only different in how the information is encoded and how its handled by the reciever.

PCM is better at rejecting interference from adjacent channels and noisey systems like gas engines with electronic ignition.

Lockout sends the reciever into fail safe mode where the servos either stay put or assume a pre programmed position, most commonly used to neutralize the control surfaces and bring the throttle to idle.

If you can afford the difference, get the PCM. If your just starting out and want to save a little upfront get FM and if you get something later on that you feel you need PCM for just purchase a PCM reciever, the difference is set in a menu in your transmitter.
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Old 07-14-2005, 12:26 PM
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Default RE: Question about Radio's

Thanks thats answered all my question ~Hellbringer
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Old 07-14-2005, 01:31 PM
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Default RE: Question about Radio's

To expand on one point. Lockout refers to PCM where if a signal is lost the servo's do nothing until Fail Safe kicks in where they either stay put or go to a pre-programmed position.

In an FM system they may move unpredicitibly making things worse. Some people prefer to "fly through" the interference with some control as opposed to pcm where they just stay put till the reciever gets x number of good frames again.

Glad to have helped.
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Old 07-15-2005, 07:14 PM
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Default RE: Question about Radio's

Is this true of all computer radios? I am looking at the JR 6102. Can I use both pcm and ppm receivers with it? How do you find out this info?

mike
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Old 07-15-2005, 09:22 PM
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Default RE: Question about Radio's

yes mike, the 6102 has both pcm and ppm,anyways mine does, go here:

http://www.jrradios.com/Products/Def...*&tag=hqlr4006
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Old 07-16-2005, 06:50 AM
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Default RE: Question about Radio's

You would have to check with the distributor but in most cases, pcm or ppm is just a menu selection that is model specific. Like I said its not changing the RF, its still an FM signal, its just different information thats being encoded and transmitted. You do have to power cycle the transmitter after you switch models to one that has different modulation. My 9C flashes PCM or PPM until you power cycle it.
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Old 07-27-2005, 10:37 AM
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Default RE: Question about Radio's

Hi, I found your discussion by doing a search, I have an Airtronics VG 400 Transmitter will PCM and PPM receivers both work with this transmitter? You talk about a power cycle of the transmitter, What do you mean by that. Is there any place I can learn about this other than bugging you good guys at RC Universe?

THANKS IN ADVANCE
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Old 07-27-2005, 01:51 PM
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Default RE: Question about Radio's

Sorry Bill but I'm talking computer radios, the VG400 is not a computer radio.

Power cycle means to change and save a menu setting then turn it off and back on so the transmitter accepts the change. Thats one of the few changes that you make that needs power cycling to commit. But again we are talking computer radios.
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Old 07-27-2005, 02:47 PM
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Default RE: Question about Radio's

Thanks for the answer, the Airtronics VG 400 IS NOT computerized so will a PCM reciever work with it, or only PPM recievers

Thanks For the Help
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Old 07-27-2005, 05:12 PM
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Default RE: Question about Radio's


ORIGINAL: propjobbill

Thanks for the answer, the Airtronics VG 400 IS NOT computerized so will a PCM reciever work with it, or only PPM recievers

Thanks For the Help


Only FM(PPM) Rx's will work with your Tx and only positive shift Rx's if you use other brands. Hitec will provide Rx's in both negitive or positive shift and there is one Hitec model Rx as well some others such as a version of FMA have a Rx that is selectable for both shifts. In addition JR Rx's are positive shift.

John
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Old 07-28-2005, 07:48 AM
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Default RE: Question about Radio's

John is correct.
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Old 07-28-2005, 09:37 AM
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Default RE: Question about Radio's

Thanks, your answers are appreciated.

THANKS
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