xescse

My Feedback: (29)

I have been told that a Positive shift Transmitter (JR & Airtronics) can not be used with a Negative shift Receiver (Futaba & Hitec).
I have a JR Transmitter (XP8103) and tried it with a Negative shift (Hitec Electron 6) Receiver a the servos operated normally.
Is this OK and do I have anything to worry about. Thanks for any information out there.

ptgarcia

My Feedback: (36)

Are you sure the Hitec was negative shift? Hitec is the smart one of the bunch and makes both negative and positive shift receivers, so it is possible your test receiver was positive pitch. If it were negative shift I don't think you would get any response from your servos. I could be wrong...

Anyway, double-check your receiver, or try the same thing with a Futaba receiver. Good luck!



Edit: fixed spelling mistakes

powertoys

My Feedback: (2)

You had a Pos shift rec. I tried a JR rec with a Futaba TX and all that the servos did was twitch a little. Even the crystals can not be switched, like taking a crystal out of a Futaba rec and putting it in a JR rec will not make the JR rec work with the Futaba TX. Tried it all one day just screwing around.

Mike

fearlessJOE

I fly pos pitch. I got SHOT DOWN by a gut with a Futaba neg pitch radio! If you dont know what you have, send it in either to the mfgr. or Radio South and find out.

Ignorance and assumption can kill!

Peter_OZ

My Feedback: (1)

I also use the JR 3810 TX and have a mix of JR and Hitec RX. The Hitecs are Supreme 7 ch PPM and work fine. Where you will run in to probs is if you try to use a Hitec PCM RX as these will not work due to the different encoding.

as the others have said your Hitec RX must be a pos shift as it would not function at all if it was neg shift.

xtals are a differnt matter and can't be interchanged between the brands as each manufactuer has xtls cut to operatate on a particular harmonic of the given Freq ( 1st, 2nd, thrird order etc) and will depend on whether it is a single or dual conversion rx.

Our Rxrs are just superhetrodyne type rxrs though have a few more smarts in them these days in the form of uP on some and advanced filters.

the RX will operate on an IF ( intermediate freq ) of 455kHz which is the output of the local osc fed into the mixer, will take the input signal of in your case 72.XXX Mhz and down convert it till it gets to 455khz, sometimes on coversion is done and sometimes 2 in the =case of dual conversion which will have 2 different IFs.

down-converted,

vIF = vRF - vLO , where vIF = the IF and vRF = the radio freq (72mhz) and vLO = the local osc freq

simple math

455khz = 72MHz - vLO
therefore vLO = 71.545 Mhz not counting for the ch freq.

normally for dual conversion the 1st If is about 3.4 Mhz then 2nd IF is 455KHz.

I won't get into the fact that the mixer also produces IF +/- 455KHz, ie sidebands and how one is removed.

then you have the fun part called modulation . . .

web site to some simple psyhiscs on simple radio theory for those interested.

[link=http://scienceworld.wolfram.com/physics/HeterodyneConversion.html]Superhet theroy[/link]

sorry I'll take my nerd hat and pen protectors off now

cheers
Peter

BobH

My Feedback: (2)

I'm surprised that the crystal won't interchange? Its osilation (freq) is independant of the phase shift.. or at least so I thought..

Selleri

I use my JR388 with Futaba receivers(not DC) without any problem what so ever.
N.B. I'm on the 35 MHz band, maybe that makes some difference?

lrb75

My Feedback: (12)

Single conversion crystals should work in any single conversion receiver (at least I've tried GWS, Hitec, Berg and JR) and any dual conversion crystal I think would work in any dual conversion receiver. I've read posts where hitec crystals have been substituted for Futaba and JR dual conversion, although I've never read about using a futaba crystal in a JR receiver?? never tried it myself on a dual conversion receiver. Chances are all the Radio Mfgs buy their crystals from the same supplier and put their own sticker on them. I would just do a range check before flying. To add to fearlessjoe's post you can't fly two planes on a single frequency even if the radios are on different shifts.

lrb75

My Feedback: (12)

Oh by the way from what I've read this shift thing is only a problem in the US. Just like the charging jacks for Futaba and JR aren't compatible in the US but apparently they are in other countries.

Hossfly

I am not familiar with the Hitec Electron however Hitec 7 channels and the Optic 6 have shift-select in the transmitter. You can go either way.
The Airtronic Stylus also has Shift Select.
JR does not. I have 783 and 8103. Recently in a question since the new 9 channel does not, I was told that JR has no intention of doing so.
I use Hitec receivers. The 8 channel is also available as a 7 channel with a select-wire to just reverse for whatever transmitter. I have half dozen of those, and same in 8 channel strictly for JR/Airtronics.

sedrick

Jr is positive shift and futaba is negative shift. Hitec offers you the option of pos or neg for the receivers.
Hitec and Royal Evo transmitters are shift select so you can use Jr or futaba receivers with these radios as long as you properly select the shift. This is US problem only. Having a frequency and shift select capable radio such as the Hitec prism or eclipse or the Royal Evo 9 or 12 channel radio gives you the most capabilities.. The royal evo is the easiest to change both frequency, shift select and model

BobH

My Feedback: (2)

I buy crystals and change them on my Futaba Rx's (lo or hi band dependant) because my 9zap has a synth Module on the Tx. I don't specify a Futaba crystal and they all have worked. I suspect there is no difference between radios with regard to crystals. There really shouldn't be any need for it..

Peter_OZ

My Feedback: (1)

depends on the order of the cut i.e what harmonic of the fundamental freq they are designed to ocsilate at. Same may interchange but I would not risk it in my plane.

They may all say the same carrier freq on them ie 72.xxxMhz but in fact they are cut to ocsilate on order of magnitude frequency, 1st harmonic , 2nd, 3rd etc etc

bobh hope you public liability insurace is up to date!! I would not risk putting other brand xtls in opposing brand radio gear, it is not desgned for that radio and may or may not work. Do you want to risk you plane becoming a missile and spearing into the crowd, pits etc?

Not worth it just to save a few bucks

powertoys

My Feedback: (2)

Your just talking buying Futaba or the like brand crystals and switching between Hi and Lo right? Not JR or something else into Futaba. Because I know that doesn't work. As for switching crystals staying in the Hi band or Low band I've done that without problems. Heck I've even seen people take a low band crystal and put it in a high band rec with out probs. Though I wouldn't recommend it.

Mike

BobH

My Feedback: (2)

Peter and Mike, I have bought crystals at Toledo and I may.. and I emphisis MAY have said they were for a Futaba Radio, I can't remember. So if that were the case then I would guess that the cyrstals I puchased would have matched my Radio exactly. I can't swear to it though. I don't mix hi and lo crystals in my Rx's, I stay with the Futaba recommendations of the channel numbers and matching Crystals. Peter I would not buy a Crystal that was incompatible with my Radio and to date none of them are. The information of the Harmonic order is usefull knowledge, thanks for sharing. I'll have to investigate to see if any of the Radio's sold on US Frequencies have a different cut to them or not. That's a discussion I have not run across in my many years of RC.