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mixing rx's with tx's

R/C Submarine modelers

Postby boatbuilder1 » Fri Dec 05, 2003 12:53 pm

is it possible to mix rxand tx brands like I have a few extra rx from futaba and would like to get it to work with the robbe radio f 14 ?
charlie



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Postby petn7 » Fri Dec 05, 2003 2:13 pm

should be as long as they are on the same shift. i dunno what shift robbe is on.
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Postby kd6hq » Fri Dec 05, 2003 4:42 pm

I normally use the Futuba R127DF receiver with the robbe F14 radio, not problem. Any of the Futaba "FM" receivers should work.
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Postby boatbuilder1 » Sat Dec 06, 2003 12:20 am

I get next to nothing and some glitching
I thought the robbe was made by futaba?????????
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Postby boatbuilder1 » Sat Dec 06, 2003 12:21 am

and what is a shift ?
do you mean FREQ
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Postby petn7 » Sat Dec 06, 2003 12:46 am

no, i do not mean frequency. i don't know exactly what shift is, but some radios have different shifts from each other. for example, one cannot use a futaba transmitter with a JR receiver since they have opposite shifts.
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Postby kd6hq » Sat Dec 06, 2003 4:33 am

Charles

As far as I know the robbe F14 is made by Futaba.

Don’t worry about the shift - I know that Futaba receivers will work with the F-14.

To me when my servos "glitch" it usually means that the batteries need to be charged but there can be many other reasons also. When you get the glitches – is anything else running? (Pumps, props, etc….)

What is the model number of the receiver are you using?
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Postby boatbuilder1 » Sat Dec 06, 2003 11:03 am

model# fp-r-138dp 8 channel pcm 1024

thanks for the help batteries are fully charged
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Postby kd6hq » Sat Dec 06, 2003 12:15 pm

Ok, this may be where the problem is the F-14 is not a PCM transmitter. I am not familiar with the PCM, as I have never used one. So if someone else can speak up here it would be appreciated. In the mean time I’ll see what I can find out.
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Postby Ramius-II » Sat Dec 06, 2003 1:05 pm

Hi All:
PCM is short for Pulse Code Modulation and refers to the type of signal that a transmitter produces. Shift is a frequency offset. In FM the signal is "wide" rather than "tall" like AM. AM is Amplitude Modulation where the transmitted power in varied up and down. FM uses a constant power and changes the frequency, typically 5 KHz of center frequency. Since we are not working with music or sound, we don't need such a large change in frequency. Thus, one maunfacturer can choose to use the area which is the primary frequency +5 KHz and another the primary frequency -5 KHz. Thus the term shift. Shift+ or Shift-. Another term is "high side" and "low side".

If I haven't put you all to sleep by now, or given you a brain cramp, ??? on a receiver there is a switch for PPM/PCM. This must match the transmitter type if the receiver is universal.

PCM is specific to each brand, so you can only use a Futaba PCM Tx with Futaba PCM Rx, Multiplex PCM Tx with Multiplex PCM Rx and so on. Many years ago, Multiplex led the way with PCM, being the first model aircraft radio to have PCM, before Futaba/JR had it. As usual, Multiplex has moved on and developed PPM with the full programmable failsafe features of PCM, so they have stopped making PCM Rx, and their latest Tx the Royal Evo does not have PCM. If you buy their older Tx such as the Profis they have PCM but you would need to find PCM Rx second hand. To get the failsafe features in PPM you have to buy a Multiplex IPD Rx, which is cheaper than buying a PCM Rx and it can be used with absolutely any brand of shift compatible PPM Tx still with its fully programmable failsafe, unlike a PCM Rx.

Ed
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