Hi.
Does anyone know if it's possible to connect two different brands of transmitters to use the teacher/student functionality? (In this case: JR->Multiplex)
I realize that I would have to make myself a custom cable, but AFAIK it's only the PPM signal that's interesting and that signal should be the same on every transmitter. (Please correct me if I'm wrong on this one).
Looking forward to your comments, /TB
Hitec and Futaba will work together but it's recommended by Hitec that you use their cord. Some of the later Hitec radios can have problems with certain trainer cords. The rumour (unconfirmed) is that some leads allow voltage to flow back from the Futaba to the Hitec, often smoking both radios. Anyone got the hot gossip on this rumour?
There was a kit for a device that allowed you to use two receivers in the model. The student and the teacher could have different brands of TX and could even have different modes. Can't remember where I saw it. You had a switch on the teachers tx that cut off the RF. then the student had control. When the teacher need to regain control he let go of the switch.
regards
Tom Watson Sydney Australia
For full details of all configurations, refer to "Buddy Boxes. Servo Leads.Simulators.Interface" e.g. TX 2 TX ***
JR and Multiplex are both "positive shift" transmitters, so if the channel functions are the same, you can probably do it. BTW, Hangar 9 makes an interface that allows Futaba and JR stuff to buddy box together.
Morris
The bad combo is Futaba master, Hitec student, and Futaba cord. The hitec cord has a diode. Without it, this combo will power the student radio, allowing it to transmit. You run the risk of shooting someone down with the student radio. Solutions are to remove the students crystal or frequency module and/or antenna, or to avoid the situation and use a Hitec buddy cord.
"AeroMutt" schreef in bericht news:b30b1$4304cbb8$d818625b$ snipped-for-privacy@NAXS.COM...
--------------------- Hi to all,
That positive shift problem of tue U.S. is of no importance, as this concerns the RF-part. As the original author of the question suggests, it's only the ppm-signal one should care about.
If you have just a little proficiency in electronics, or not even electronics, just electrics and you know which side of a soldering iron is hot, then you can make a buddy lead that would probably work between JR and Multiplex. And if it does'n work, it will do no harm. You even can reverse polarity of the signal, if signal is reversed, it will work. If it finally does'n work, probably the signal must be a little manipulated with a few electronic components, but unfortunately, then I cannot help anymore. Anyway, as Alan Tong's excellent RC-URL-list mentions, refer to my website for full details :
Olivier
| That positive shift problem of tue U.S. is of no importance, as this | concerns the RF-part. As the original author of the question | suggests, it's only the ppm-signal one should care about.
Yes, but the PPM signal is exactly where the shift _is_.
It would be a simple matter to change the shift from one to another (needing probably only a single chip) but if your buddy cord doesn't take that into account, then it's not going to work.
Even the site you mentioned mentions this. Look at this picture --
He also says this --
A transmitter with a positive PPM modulation will in theory not be compatible with a transmitter working with a negative PPM-modulation. In practice, my FC18V3Plus seems to understand sometimes an opposite PPM-signal
He then says that `this has nothing to do with the positive and negative SHIFT system which applies to the United-States and Canada', which is probably what you're thinking of, but I'm not so sure I agree.
Either way, he seems to think there is a problem -- and so do I. I'm not sure I agree with him about the _source_ of the problem, but I'll admit that he's done a lot more research on it than I have, so he may very well be correct.
| If you have just a little proficiency in electronics, or not even | electronics, just electrics and you know which side of a soldering | iron is hot, then you can make a buddy lead that would probably work | between JR and Multiplex. And if it does'n work, it will do no harm.
There is potential to do harm. Depending on the transmitter brand, some master boxes provide power to the slave box. If you get that power into the wrong pin, you could fry something.
| Anyway, as Alan Tong's excellent RC-URL-list mentions, refer to my | website for full details :
And a fine site it is.
Either way, as long as you're not doing PCM, you can usually work out buddy box connections between most brands of transmitters now.
"Doug McLaren" schreef in bericht news:uogNe.154931$ snipped-for-privacy@tornado.texas.rr.com...
Hi again,
As you didn't seem to notice, I am the author of the site
As you say, however, "Either way, as long as you're not doing PCM, you can usually work out buddy box connections between most brands of transmitters now." And you are very correct by saying "Depending on the transmitter brand, some master boxes provide power to the slave box. If you get that power into the wrong pin, you could fry something." That's why I suggest in chapter 2 about making buddy leads the following : "In any case and as mentioned before, I dissuade everybody to use a lead that gives battery-power from master to pupil transmitter"
In chapter 6, there's an (incomplete yet) overview of what type of transmitters have been connected to each other. There have been several Graupner transmitters as slave connected to a Multiplex transmitter. As Graupner is rather similar to Jr for some models... Unfortunately, I have nearly no (or not at) all feedback from the US (where JR is so popular) about people connecting different brands to each other. Probably the doom of the FCC has something to do with it.
Olivier
Hitec and Futaba TX and RX are fully compatible except for PCM systems. Both must be set to PPM if linked together - neither will operate the other's PCM RX. There is no diode in the Hitec lead, Pins 4 & 5 are simply soldered together at the student end only.
Hitec Laser and Eclipse can also buddy mode 1 to mode 2 and vice versa.as if both are on the same mode.
NB: the new Futaba 9C uses a unique square plug.- reason could be that it is more compact and the plug and cord are almost flat to the TX case and not so easily damaged as the round type used on earlier models. see =
Futaba 9ZHP has 5V + through centre pin which is earthed to plug shield on Hitec buddy boxes, not a good combination.
It is now possible to connect JR to Hitec or Futaba. refer to 'Buddy Boxes. Servo Leads.Simulators.Interface" at Alan's Hobby Web Links
regards Alan T. Alan's Hobby, Model & RC Links
| > Either way, he seems to think there is a problem -- and so do I. I'm | > not sure I agree with him about the _source_ of the problem, but I'll | > admit that he's done a lot more research on it than I have, so he may | > very well be correct. ... | As you didn't seem to notice, I am the author of the site |
Yes, I missed that.
| I live in Europe, where that positive and negative shift is | non-existent.
Right, but it seems an awfully big coincidence that in the US, the same brands that have a positive modulated PPM shift also have a positive RF shift, and the same brands that have a negative modulated PPM shift also have a negative RF shift.
What seems likely to me is that the PPM shift is the _cause_ of the RF shift, and outside of the US the manufacturers simply added a bit of circuitry to reverse the shift before feeding it to the RF stage, or perhaps the RF stage itself reverses it. (I wish they'd done that over here, but I guess it saved a bit of money for Futaba and Hitec by omitting the components.)
This would be a relatively easy thing to verify -- I would take a JR TX as a buddy box, and connect it to a Futaba TX master (doing no translation of the PPM signal in the trainer cord), then see which brand of RX works with it. If a JR RX works (with the Futaba TX, but the PPM signal coming from JR), then I'm correct. If the Futaba RX works, then I'll be confused. If neither works, then you'll be right.
Since you're not in the US, you probably don't have any US RC equipment, so any verification of this will probably have to be done over here. I'll see about setting up the test if I get a chance.
| Altough this positive and negative shift is nonexistant for the old | continent (all transmitters I had in my hands are exclusively positive | shift), the PPM-signal of some transmitters I had in my hands are positive, | some are negative. This just as proof that the negative and positive shift | is only related on how that PPM signal (be it positive or negative) is send | : either frequency shift below the carrier, either the frequency shift above | the carrier-frequency.
It's not proof, as I've suggested. (And it's not really possible to prove anything anyways, only disprove. It may suggest this, but I do have an alternate explanation, one that can be verified (but not proven, of course.))
| Unfortunately, I have nearly no (or not at) all feedback from the US | (where JR is so popular) about people connecting different brands to | each other. Probably the doom of the FCC has something to do with | it.
I'll bet it's more economics than `FCC doom' -- by not standardizing the shifts in the US, Futaba and Hitec probably saved $0.15 per transmitter or so. Also, they may see some value in not being compatible with JR and Airtronics.
As for JR being so popular over here, it seems to vary a lot. At the glow club I fly at, Futaba reigns supreme. At the glider club it's JR. Hitec is a distant third at both, especially with low end equipment, and Airtronics is very rare. The glider club also have a few Multiplex users. The glow club has never heard of Multiplex :)
I understand that English is not your first language. However, I do not know how to put past posts in more simple English.......... Whenever connecting a buddy box, the module and/or crystal should be removed from the buddy box - no matter which brand of TX is used. Not only will this prevent extraneous transmissions, but in buddy boxes which require a battery to be in place (do not turn on - plug in activates power) as in JR, and computerised TX.this almost doubles the battery on time as you are not generating RF. There is definitely no diode in a Hitec Trainer Cord. Two pins of the Hitec Trainer lead are shorted together at the student end. This is the same as PC Simulator leads for Hitec & Futaba 6 pin DIN plugs. The Hitec Trainer lead is preferred for both use with Futaba TX with a round
6 pin DIN socket and Hitec systems, as it is not only longer and much more flexible it is usually better priced. Once more, please refer to "Buddy Boxes. Servo Leads.Simulators.Interface" at Alan's Hobby, Model & RC Web Links
Perfect! Please keep in touch if you ever find something that would confirm you view! As my electronic knowledge is much to restricted and as I never had any confirmation on the RF-signal having the same sign as the ppm-signal, I am curious.
OK, not a proof indeed.
Thanks for you critical view on this matter, indeed.
Olivier
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