vasek

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what is the difference between those two mod.?

laryboy

My Feedback: (2)

Modulation-this is the type of radio signal you want to use on each model. There are three different modes depending on which receiver and you are using. PPM, ZPCM, and SPCM. PPM is like normal "FM" and is used with the JR RF200 receiver and other after market FM receivers. ZPCM is "Pulse Code Modulation" with a 512 step resolution and is used with JR's 233 Receiver. SPCM is "Pulse Code Modulation" with a 1024 step resolution and is activated when using the JR 330 PCM receiver

vasek

My Feedback: (4)

thanks laryboy, but I am still a little confused...

I am getting the PCM9XII with the syntesizer so I can choose any ch. , the Tx comes with the R900S (SPCM). I was just wondering why I would use the ZPCM ?

I believe, to use failsafe I cannot use PPM... if you or anyone else can elaborate a little more.

carrellh

Some of this may not apply to JR equipment but it is decent general info

http://www.futaba-rc.com/faq/product-faq.html#q16

The original PCM radio systems had a servo resolution that was 512 points on the 60 degree rotation. The newer equipment offers 1024 points, or a resolution two times better than the previous 512. Depending upon what model of PCM transmitter you own, it will be able to use EITHER 512 OR 1024, not both. So you need to know which type your radio uses. To make this easy, Futaba labels the face of the 1024-type transmitters and receivers with "1024". If JR is like Futaba, your transmitter is either capable of SPCM or ZPCM but not both.

Further down the page
There is no range increase in going to PCM; however, there is marked improvement in noise reduction, and in safe performance during the time noise is received. Basically, PCM takes your radio's FM signal and 'scrambles' it. Then the PCM receiver descrambles it and utilizes it. Random noise from other items are not going to be mistakenly read as proper servo instructions as can happen with an FM.
Also, PCM does not transmit position signals for each servo in each pulse. Rather it submits movement commands and occasional position confirmation commands. This way, if a stray signal DID tangle up with your existing command string it is not likely to affect all channels because many channels commands are not currently being sent.
FailSafe: If your PCM receives interference, it maintains the last task it was doing until a preset time you program in your radio. If it continuously receives interference past the preset time it then obeys the commands you set in the transmitter (for example on giant scale gas planes we set failsafe to shut down the kill switch and throttle and leave all other surfaces in the same position).
The transmitter periodically sends commands to the receiver that are to be used in the event of a failsafe situation. When the receiver determines a failsafe situation is occurring, it obeys these stored commands. In a battery failsafe situation it obeys only the throttle command but obeys regular transmitter commands for all other channels. It continues to analyze the transmitter's commands for throttle, and when the transmitter command is the one set as the 'reset' for the failsafe is received then it releases the failsafe hold on throttle.

vasek

My Feedback: (4)

thanks Carrell [sm=thumbup.gif]

Mac_Man_UK

The JR Transmitters USUALLY have all 3 types of modulation available. However, as the Z type is old, JR no longer manufacture the Z type receiver and some transmitters no longer have this function available. With the PCM9XII, Z type modulation is still embedded and available to the user.

I would expect the next series release to drop Z type completely.

rmh

MacMan has it right
Other than the "feel"of the servo as it moves -512 and 1024 steps-- radios act the same.
My 9 (9303 in US) channel does not display it and I won't bother to have it activated .
My 10x has all three -and I recently flew both Z and S receivers with new servos - just to see what the apparant differences were .
One is really hard pressed to tell on good ,new servos.
The operation of the twin elevator servos was the only place I could see any difference.
On the old 512 radios the mix function was awful -and there was plenty of error in this application.
512 is going away -just like 56 k dial up on computers. My new computer setup is fibre optic -into the house and upload and download is -fast- just under a T3 -- all for 33 bucks a month- The new radios are the same deal - no advantages to to using the old setups -New RX are available in SPCM for very little money and all around, much better.

stek79

Hello Dick,
do you mind explain more in detail that dual elevator behaviour under 512 setps mod? Just for curiosity...

There are timing errors on fast movements, or also errors in position holding? And in flight, could you tell the difference?

Interesting experiment!