DragonHeart

Hi,

Ok this may sound stupid but im gonna ask anyway lol.

If u have a futba radio do you have to use a futba reciver or can u use a different make with it ie :GWS etc ?

Im gathering you would have to use the same make, but never hurts to ask

Jack Hyde

My Feedback: (1)

Some txs emit a positive pulse signal and work with rcvrs that use a positive pulse signal - Airtronics is a positve pulse system. Hitec is negative pulse, so is Futaba I think. I have a Hitec Eclipse radio that can be programmed to transmit + or -. The Airtronics RD 6000 can be programmed to put out + or -. I have used Hitec rcvrs with the RD 6000 and Airtronics rcvrs with the Eclipse. It is done all the time. So it can be done but only with compatible sets.

Montague

Not a stupid question at all.

You may, in fact, mix and match brands of transmitters and receivers. But there are some limitations.

Talking about only FM here for a moment, as that's most common. With FM, there are two ways to "shift" the signal. Futaba and Hitec go one way, JR and Airtronics go the other. So you can't use a JR reciever with a Futaba TX

Then you get to companies like GWS, FMA, Hitech (with their after-market RXs) and several others. They all sell FM receivers in "Futaba" and "JR" flavors. So, when you order a GWS receiver, you specifiy if you want Futaba compatibility or JR/Airtronics compatibility.

Now, each receiver uses a crystal. You use the crystal that matches the receiver, regardless of the transmitter. So use a GWS crystal in a GWS receiver when using it with your Futaba transmitter.

PCM is a different animal. In general, PCM receivers only work PCM transmitters from the same company, and sometimes not all PCM TXs from the same company. (1024 vs older 512 PCM for example).

And to really confuse things, there are receivers out there that can be switched from Futaba to JR compatible. Hitech and FMA both make some that do this, either with a switch or they actually auto-detect what kind of TX is sending out the signal.

And finally, there are a couple of Transmitters (Hitech Eclipse with the Spectra module and the Polk Tracker II) that can be set to Futaba or JR shift, allowing them to work with any FM Receiver.

Personally, I have a JR and a Polk transmitter. I have a mixture of FMA, Hitech, JR, Futaba (just 1), and GWS (just 1) recievers.

Crash90

My Feedback: (17)

I have used 3 receivers successfully with my futaba transmitter.
Futaba
GWS
and the M5 receiver. I forget who makes it.
They are the only ones I have tried.

Montague

The M5 is made by FMA

Spaceclam

futaba and hitec are negative shift. airtronics and jr are positive shift. gws makes both positive and negative shift recievers, you just have to specify. as long as your tx and rx are on the same channel and the same direction pulse, they will work fine.

Montague

Oh, one funny side note, different companies sometimes number their channels differently. When I moved some of my planes over from my older JR radio to my Polk, I had to go unplug the servos and replug them in different channel slots.

DragonHeart

Thx guys for your answers

Spaceclam

that's true, i forgot about that.

Steve Lewin

Dragonheart,

Careful ! All of the information above applies only to the US and their 72MHz frequency band. Given in good faith I'm sure but by people who forget that America is not the whole world .

If you are in the UK, using 35MHz (or in the rest of the world) it's much easier because we don't have all that positive/negative rubbish. *All* makes of PPM (sometimes incorrectly called FM) transmitter and receiver will work together. Only for PCM do you have to stay with the same make.

Steve

DBCherry

My Feedback: (4)

Good to know Steve. To be honest, I generally don't think to look at the country of origin before replying. I should change that.

Makes me happy that I hadn't seen this to respond to.
Dennis-

Spaceclam

same here. they are these little tiny letters in a place where you don't even look. you want to read the post, not the jagon to the left

Montague

Yes it is, "W" says so. j/k

Acutally, I did notice the UK as the location, but I didn't know that all the transmitters shift the same way on 35Mhz. I wonder why this is. Do you know if everyone is shifting positive or negitive? I wonder why whichever manufacturer shifts one way on 72Mhz and the other way on 35Mhz does things that way.

While writing this, it occued to me that they could be shifting "both" ways on 35Mhz, which again leads me to wonder why it's different on the two bands.

Actually, as I understand it, PPM is, in fact properly called PPM/FM (or was that FM/PPM, I forget). Neither PPM or FM alone is actually acurate. PPM is Pulse Position Modulation and PCM is Pulse Code Modulation. Both both describe how the data is organized, but not necessarily how the wave is actually affected.

PCM is usually FM. You could, in theory, have an AM PCM system, though I doubt anyone has done so. So, when you say PCM, it's clear you mean FM/PCM. The existing AM and FM sets are all PPM, which is why PPM is shorted to "FM" rather than saying FM/PPM all the time.

At least that's how I understand it.

Spaceclam

i don't understand it at all

Steve Lewin

The world outside America (if it exists ) uses +ve shift. I have no knowledge of why Futaba/Hitec chose to do something different on 72MHz.

The cynical among us might think that the US is a big enough market for them to want to lock people into their kit i.e. prevent people from easily switching or mixing brands. But I couldn't say. Certainly there are no technical benefits to either shift.

As for PPM/PCM, if you're going to refer to just the PCM coding method and not mention that's it's transmitted over FM I'd suggest that it's a lot more logical to refer to PPM (the coding method). Talking about an FM Tx when you mean PPM, knowing full well that PCM is also FM is just technically wrong. Still I can tell I'm swimming against the tide with this one. It won't be the first time...or the last .

Steve

Montague

Steve,
Thanks for the info the rest of the world as far as shift direction goes. Very strange stuff there. I do wonder why Futaba did what they did for the US market. (If I had to guess, I'd say that Hitec followed Futaba's lead there. Could be wrong though.) Of course, it's also possible that Futaba chose to use that shift to be compatible with the domestic companies like Ace and Kraft that used to be dominant in the states. I have no idea if either Ace or Kraft ever produced an FM set though. Before my time.

You are absolutely right about the whole label thing for PPM vs PCM, FM vs AM kind of thing. It's just common useage, probibly due to the order the various tech has evolved. First there was AM/PPM, and no one bothered saying anything, it was just a radio .

Then there was FM/PPM, but it was only differnt in that it was FM, so all the ads had "IT's FM!!!" in big letters, and the transmitters all had "FM" stamped on the front pannel. So, now we had AM and FM transmitters.

Then along comes PCM. And all the ads say "PCM! It's better!". You get the idea.

So, now we have 3 types of transmitters, all of which are referred to by somewhat incorrect short hand terms . But we know what we mean, and the stuff works (most of the time)

Montague

You know, I thought I saw a post by a rep from Futaba on here the other day. Maybe we can get some hard info?