RC Radios, Transmitters, Receivers, Servos, gyros Discussion all about rc radios, transmitters, receivers, servos, etc.

Why isnt my Futaba working with Jr receiver?

Reply

Old 10-08-2003, 03:16 PM
  #1  
faisalk
Senior Member
Thread Starter
 
Join Date: Apr 2003
Location: karachi, PAKISTAN
Posts: 313
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Why isnt my Futaba working with Jr receiver?

I just bought a Futaba 9cap transmitter only on 35 mhz. People told me that on 35 mhz futaba transmitter will work with Jr receivers. The problem is that it does not seem to be working. The servos are not taking any signals from the transmitter. The receiver is a single conversion receiver, do you think may be this is the problem? Also I am using a Jr crystal in the transmitter, I know it is not advisable as it reduces range but it should atleast take signals from one feet. Help plz!
faisalk is offline  
Reply With Quote
Old 10-08-2003, 03:22 PM
  #2  
james yeram
Member
My Feedback: (5)
 
Join Date: Sep 2003
Location: Oceanside, CA
Posts: 72
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

wow don't even fly if it works.
very unsafe.
futaba uses the dual conversion crystal. if you want to try the jr thing try using ppm instead of pcm that might be your problem.
james yeram is offline  
Reply With Quote
Old 10-08-2003, 03:24 PM
  #3  
sdavied
Senior Member
My Feedback: (4)
 
Join Date: Sep 2002
Location: Ellis, KS
Posts: 112
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

To my knowledge JR and Futaba are not compatible. I believe the signal coding is different. And also, 72 mhz is the only band available for R/C aircraft, unless you are a HAM. Then you can get radio systems on 50 mhz. I think the 35 you are refering to is the channel. The channel number has nothing to really do with frequency. It is an arbitrary number assigned to the frequency.
sdavied is offline  
Reply With Quote
Old 10-08-2003, 03:25 PM
  #4  
faisalk
Senior Member
Thread Starter
 
Join Date: Apr 2003
Location: karachi, PAKISTAN
Posts: 313
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

I already tried ppm. Is there dual conversion and single conversion in transmitters too or just in receivers?
faisalk is offline  
Reply With Quote
Old 10-08-2003, 03:51 PM
  #5  
tadawson
Senior Member
 
Join Date: Sep 2002
Location: Lewisville, TX
Posts: 669
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

sdavied -
Dude, check again. This guy is in Pakistan - they are on teh 35MHz BAND, not 72MHz. My understanding was that the shift is the SAME on all but 72MHz between Futaba and JR. I have no idea why you would put a JR TX crystal in the Futaba TX - just stick with the Futaba crystal. You WILL need to use PPM receivers, though, and the JR and Futaba PCM signal encodings are different no matter what band you are on.
tadawson is offline  
Reply With Quote
Old 10-09-2003, 12:10 AM
  #6  
GalenB
My Feedback: (18)
 
Join Date: Dec 2001
Location: Issaquah, WA
Posts: 2,141
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

This is also how I understand non-US transmitters and receivers to work. They all have the same shift so they should in theory be compatible. As already mentioned -- I think you should get a Futaba crystal for your Futaba receiver...

Please keep us posted as to how this works out.
GalenB is offline  
Reply With Quote
Old 10-09-2003, 03:03 AM
  #7  
HarryC
My Feedback: (1)
 
Join Date: Feb 2002
Location: private, UNITED KINGDOM
Posts: 3,560
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

Futaba 9cap transmitter only on 35 mhz.Also I am using a Jr crystal in the transmitter,
That is problem number one. You must use that manufacturer's crystal in their piece of equipment. No ifs or buts or well it seemed to work ok. Futaba Tx means Futaba crystal and nothing else.

The JR Rx must have a JR crystal. The Tx does not know if the Rx is single or dual conversion, it is just an issue in the Rx and works transparently with any Tx.

Are you sure both are PPM? The Rx needs to be PPM. The Tx can be set to PPM or PCM, it must be set to PPM.

H
HarryC is online now  
Reply With Quote
Old 10-09-2003, 05:16 AM
  #8  
ReallyUglyStick
Senior Member
My Feedback: (5)
 
Join Date: Feb 2002
Location: Cary, NC
Posts: 207
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

i think he meant jr crystal in the rx, unless his model is different than the us 9cap's. the 9c's come with a module in the tx.
ReallyUglyStick is offline  
Reply With Quote
Old 10-09-2003, 06:07 AM
  #9  
faisalk
Senior Member
Thread Starter
 
Join Date: Apr 2003
Location: karachi, PAKISTAN
Posts: 313
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

Mine is also with a module but there is a crystal inside the module which specifies the channel number.
faisalk is offline  
Reply With Quote
Old 10-09-2003, 06:22 AM
  #10  
faisalk
Senior Member
Thread Starter
 
Join Date: Apr 2003
Location: karachi, PAKISTAN
Posts: 313
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

Harryc I have set it to ppm but still it is not picking up any signals. you know for a fact that with a jr transmitter crystal in futaba transmitter it wont pick up any signals or it should pick up signals with reduced range?
faisalk is offline  
Reply With Quote
Old 10-09-2003, 10:01 AM
  #11  
HarryC
My Feedback: (1)
 
Join Date: Feb 2002
Location: private, UNITED KINGDOM
Posts: 3,560
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

I don't know how a Futaba Tx reacts with a JR crystal in it, but I would not be at all worried if it did not work. If it does not work with a Futaba crystal, then is the time to be worried!

The crystals we use do not vibrate at the frequency of our "channel". They work at much lower frequencies and part of the circuit multiples the crystals vibrations to get to the transmitted frequency. Multiplex uses crystals half the transmitted frequency and actually marks them with the crystal frequency e.g. 17point something Mhz instead of 35point something Mhz. I don't know what JR and Futaba use, but just suppose one uses crystals of 1/2 frequency and the other uses 1/3 frequency, they will never work in each other's Tx. Even if both use the same fraction that doesn't mean they will work. The different circuits may be designed for crystals of different properties, to manipulate the excitation of the crystal and its output.

In other words a JR crystal in a Futaba Tx tells you nothing about whether the Tx is working or not. We use Fut Tx with JR Rx and JR TX with Fut Rx all the time, so it does work.

H
HarryC is online now  
Reply With Quote
Old 10-09-2003, 10:59 AM
  #12  
mr.rc-cam
Senior Member
 
mr.rc-cam's Avatar
 
Join Date: Jun 2002
Location: West Coast, CA
Posts: 536
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

As mentioned, many of the JR Rx's are single conversions designs. Futaba uses dual conversion. The Xtals are quite different in these two cases.

Also, the pullability spec of the various Rx xtal brands can differ. So, often it is not wise to mix brands even when they seem to work.
mr.rc-cam is offline  
Reply With Quote
Old 10-09-2003, 05:56 PM
  #13  
The_Matrix
Senior Member
 
Join Date: Jul 2003
Location: Red Springs, NC
Posts: 134
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

To put it in simple terms. You cannot use a JR reciever with a Futaba Transmitter, it simply will not work. They are not compatible. JR uses positive shift and Futaba uses Negative shift. You can use JR servos with a Futaba system or Futaba servos in a JR system, but not mixed TR and RX. JR is compatiable with Airtonics however, and you can mix those systems. You may also mix Futaba systems with Hitec or Tower Hobbies brand.
The_Matrix is offline  
Reply With Quote
Old 10-09-2003, 06:28 PM
  #14  
Mac_Man_UK
Senior Member
 
Mac_Man_UK's Avatar
 
Join Date: Jul 2003
Location: Slough, UNITED KINGDOM
Posts: 1,415
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

To give Harry some extra info.....

The JR Transmitters use cyrstals labelled at the Transmit frequency but oscillate at 1/4 the freq. The transmit module / board uses 2 stages of frequency doubling to give the final RF Frequency. JR kit uses a deviation of +/- 1.8KHz which is generated at the xtal fundamental.

The JR receiver ( unless a Dual Conversion ) uses an IF of 455KHz. The crystal oscillates 455KHz lower than the marked frequency. ( BTW the Xtal runs at 3rd Overtone ). This generates a mix signal of RF Frequency, Xtal Frequency, Xtal + RF Freq, and RF - Xtal Freq. This combined siganl is filtered to leave only a 455KHz IF.

Dual Conversions receivers have another IF of 10.7 MHz in addition to the 455 KHz IF.

For more info on the benefits of DC & SC, there is an interesting article here....

http://www.bergent.net/SC-DC.pdf
Mac_Man_UK is offline  
Reply With Quote
Old 10-09-2003, 06:40 PM
  #15  
HarryC
My Feedback: (1)
 
Join Date: Feb 2002
Location: private, UNITED KINGDOM
Posts: 3,560
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

To put it in simple terms. You cannot use a JR reciever with a Futaba Transmitter, it simply will not work.
If you read this thread, and many other similar ones you will learn that Futaba and JR are perfectly compatible. It is only for the North American market on 72Mhz that Futaba makes a special effort to make its product different to that which it makes for the whole of the rest of the world. For some reason Futaba shafts American customers, to lock them in to its products. For the rest of the world Futaba only makes positive shift radios. Hitec just copied Futaba in the USA, again for everyone else in the world Hitec makes positive shift radios. Those of us outside the USA had never even heard of shift incompatibility until we read about it from Americans on the web forums.

H
HarryC is online now  
Reply With Quote
Old 10-10-2003, 01:12 AM
  #16  
faisalk
Senior Member
Thread Starter
 
Join Date: Apr 2003
Location: karachi, PAKISTAN
Posts: 313
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

I am waiting for my futaba transmitter crystal. As soon as i receive it I will clarify all you guys on the issue of compatibility.
faisalk is offline  
Reply With Quote
Old 10-10-2003, 07:28 AM
  #17  
ReallyUglyStick
Senior Member
My Feedback: (5)
 
Join Date: Feb 2002
Location: Cary, NC
Posts: 207
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

why didn't your module come with a crystal in it? the module is supposed to be the self contained rf section of your tx. the whole purpose of the module is to swap them out, not pull the crystal out of them. i'm quite sure they aren't even designed to have crystal pulled out of them.
ReallyUglyStick is offline  
Reply With Quote
Old 10-10-2003, 07:44 AM
  #18  
faisalk
Senior Member
Thread Starter
 
Join Date: Apr 2003
Location: karachi, PAKISTAN
Posts: 313
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

reallyuglystick i think you yourself dont know much about this stuff. The module came with a crystal but the channel number does not match with my jr receiver crystal(The crystal in Futaba transmitter is 35.850, whereas crystal in all 3 of my jr receivers is 35.190) I think the purpose of module is to change the frequency band (for eg. if in UK you are using 35mhz and you go to usa you just change the module and you can use your same transmitter on 72mhz by putting a 72 mhz module) The crystal in the transmitter should match with the crystal in the receiver. I have 3 planes and all 3 receivers have the same crystal i.e 35.190. Now if I buy a new transmitter I wont change the crystal in all 3 of my receivers to match the transmitter crystal. I will just change the crystal in transmitter to match the receivers.
faisalk is offline  
Reply With Quote
Old 10-10-2003, 09:03 AM
  #19  
HarryC
My Feedback: (1)
 
Join Date: Feb 2002
Location: private, UNITED KINGDOM
Posts: 3,560
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

Faisalk is correct. Again this is a difference between the USA and the rest of the world. We are allowed to change crystals in transmitters, from top to bottom of the band. I don’t know if the USA’s FCC is just being cautious or if there is good reason because errors in the crystal get magnified twice as much at 72 Mhz as they do at 35Mhz. Hard to believe that’s the reason though, because in the USA Multiplex has a dispensation from the FCC that allows Multiplex users to change the crystals without needing a qualified technician to re-tune the radio! Perhaps it suits Futaba and JR not to apply for dispensation like Mpx did, so that they boost sales of modules?

H
HarryC is online now  
Reply With Quote
Old 10-10-2003, 11:41 AM
  #20  
Troy Newman
Senior Member
 
Join Date: Dec 2001
Location: Goodyear, AZ
Posts: 2,429
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

Its possible to swap crystals in both Futaba, and JR modules.....This is not recomended but I personally do it all the time...Do a good range test and check it out...you should be fine.

The crystals on both modules are easily accessed without tking the modules apart.


As for running a Futaba Crystal in a JR module or RX or vice versa this should not be done. As for the Shift issue I don't know but the US market is different and I suspect that on 35mhz Futaba, JR and Airtronics all may talk to each other. I don't know this for sure but it is possible.
Troy Newman is offline  
Reply With Quote
Old 10-10-2003, 02:10 PM
  #21  
faisalk
Senior Member
Thread Starter
 
Join Date: Apr 2003
Location: karachi, PAKISTAN
Posts: 313
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Why isnt my Futaba working with Jr receiver?

Another question how much does your 9cap last on a full charge? mine is only lasting for 2 hrs whereas my Jr was lasting atleast 5 hrs.
faisalk is offline  
Reply With Quote

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service