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SPCM or PPM

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Old 03-29-2006, 10:56 AM
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tfarmer96
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Default SPCM or PPM

I just got my Jr 9303. I have been going though the programing for my planes and it gives me a choice to use SPCM or PPM. I have slimline JR700 RX in all my planes. What is the difference in SPCM and PPM.

Thanks.
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Old 03-29-2006, 11:48 AM
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js3
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Default RE: SPCM or PPM

I believe "S" is newer technology than "Z" but don't quote me on it. I know that I have to match the TX (SPCM or ZPCM) to whatever type of modulation the RX will accept. As for the differences between S and Z, I don't really know. I'll keep an eye on this thread hopefully to find out.
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Old 03-29-2006, 02:11 PM
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Default RE: SPCM or PPM

I certainly don't claim to be an expert, but can tell you as I understand it. PPM is basically FM, if you have an FM rx, then your tx must be set to PPM. SPCM is the new version, ZPCM is an older version of the PCM models from JR.
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Old 03-29-2006, 02:16 PM
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tfarmer96
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Default RE: SPCM or PPM

so I should use PPM instead of the SPCM setting. I haven’t even tried it out on my rx yet. I think the 700 slim lines are just plain old FM
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Old 03-29-2006, 02:37 PM
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Richard L.
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Default RE: SPCM or PPM

Yes, use PPM with your 700 receiver. I'm slowly replacing all my 700 receivers with 770S receivers because I prefer to use SPCM modulation better (no glitches).
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Old 03-29-2006, 02:43 PM
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Default RE: SPCM or PPM

thats what i was looking for thanks!
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Old 03-29-2006, 03:27 PM
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Default RE: SPCM or PPM

Sorry, I misread your subject line and thought you were asking about the differences between SPCM and PCM rather than PPM.

The modulation required is always defined by the RX (other than the synthisizing systems).
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Old 03-29-2006, 03:30 PM
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Default RE: SPCM or PPM

By the way, I have had a 9303 for one year now, you are going to love it!!!
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Old 03-29-2006, 07:50 PM
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Default RE: SPCM or PPM

PPM is an FM transmission and SPCM is a PCM transmission. which one you use depend on the receiver. The receiver it came with is more than likely a SPCM receiver. but don't rely on that, a 700 is a ppm reciever
kinda easy to tell.

IF your receiver is PCM and it set to PPM it won't work.

If your reciever is FM/PPM and your Tx is set to PCM then then the servo will jitter and shake and have little to no control over them
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Old 03-30-2006, 01:56 AM
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JohnW
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Default RE: SPCM or PPM

As for the diff, I believe the ZPCM can resolve 512 step and the SPCM can resolve 1024 steps, but then again I fly Futaba, so I'm not 100% certain on that one.
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Old 03-30-2006, 07:48 AM
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pettit
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Default RE: SPCM or PPM

Sorry to burst someone's bubble, RedFox, but here's how it works:

PCM, XPCM, ZPCM, PPM, they're all transmitted using Frequency Modulation, FM.

It just depends on the method in which the information is used to modulate the frequency.

PPM, Pulse Positiion Modulation, is plain old FM as we all like to call it. The data is used to shift the frequency of the RF signal coming from the transmitter.

PCM, ZPCM, XPCM, are all Pulse Code Modulation techniques, different from one another, but still just digital information being used to modulate the RF from the transmitter.

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Old 03-30-2006, 09:56 AM
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Default RE: SPCM or PPM

I also have a 9303. For the 700 receiver, and I have one, you need to set PPM. For the 770 receiver, set SPCM. They are both nice little receivers.

As was mentioned earlier, ZPCM is the older 512 step receivers and SPCM is the newer 1024. I don't think JR sells any of the ZPCM receivers any more.
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Old 03-30-2006, 11:20 AM
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Default RE: SPCM or PPM

Sorry to burst your bubble....[:'(]
I have never heard of XPCM.
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Old 03-30-2006, 08:23 PM
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Default RE: SPCM or PPM

yep, I understand the true differance. this is just an internet forum, going into full detail I didn't feel nessasary, my bad I guess
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