Red Max

Can you use a JR receiver crystal with a Futaba radio transmitter as long as it is the same frequency?

LesUyeda

That is NOT advised. Not all crystals are created equal. There are different "cuts", requireing different cirquitry. They may appear to work, then fail, at, of course, the most inappropiate time.

Les
WA6EER

BarracudaHockey

My Feedback: (11)

Its illegal to change transmitter crystals without the proper training. If you have to ask that question, one could assume you dont have the equipment and expertise to verify that the transmitter is on frequency.

airbusdrvr

Someone will chime in soon with the right answer. Hitec and Futaba are compatible. Having only used JR/Spektrum 2.4Ghz systems I don't know what other(if any) systems are compatible with JR 72Mhz transmitters. If any other brands(i.e. Airtronics, etc.) were compatible, someone will respond. Good Luck Somehow, I think Barracud Hockey's answer missed your initial question.

exeter_acres

My Feedback: (2)

it is STRONGLY suggested that you do not "mix" brands in this area.. while a Hitec crystal "may" work in a Futaba RX, or vice versa, they are not properly tuned for each other......

prichiuso

AHH the mystery of crystals !!! None of the radio manufacturers who make crystal controlled radio systems manufacture crystals. They are bought as parts, the same way as resistors, capacitors, transistors or integrated circuits. The crystals are manufactured and tested to very stringent requirements (required by the FCC). Early radio systems had the crystals, both transmitter and reciever, soldered permanently into the circuits. This was done because of the wide tolerances of the other electronic components. Resistors could vary 10%, capacitors could vary 20 to 25%. This required each transmitter and receiver to be tuned to the particular frequency it operated on. With today's modern components and large scale integrated circuits, it is possible to make a transmitter and receiver that can operate over a wide band of frequencies by changing crystals. While it is technically illegal to change crystals in a transmitter (some radios avoid this by using a single frequency module or a synthesized frequency module) most modern recievers will operate at the frequency of the crystal installed. Receivers operating on 27, 72 and 75 MHz use a signal detector called a superheterodyne (superhet for short). For a single conversion reciever the crystal frequency for a given channel is actually 455 KHz above or below the nominal channel frequency. The tuning circuit of the receiver creates an intermediate frequency by mixing the recieved signal with the crystal frequency. This is then filtered and the pulse train is decoded and sent to the output. A dual conversion receiver does the same thing only with two intermediate frequencies one at 10 MHz and then at 455 Khz. So in effect there are only 4 types of crystals (aside from physical dimensions). A single conversion crystal cut ABOVE or BELOW nominal frequency or a dual conversion crystal cut ABOVE or BELOW nominal frequency. AM or FM makes no difference. In short, if the crystal works in your receiver it will work fine.

fizzwater2

My Feedback: (61)

But re-read the original post - was the question can you use a JR RECEIVER crystal in a Futaba TRANSMITTER.

No. You can't. Receiver crystals are cut to be off of the desired frequency by the amount of the IF in the receiver - and as such, won't transmit on the correct frequency should you put one in a transmitter, even if you did get it to oscillate.

BarracudaHockey

My Feedback: (11)

Yup, I read the initial post incorrectly.

Red Max

Okey my origional question was: Can I use a JR Receiver in my airplane and use a Futaba radio, as long as I have the same frequency crystals in my trans. and receiver???

BuschBarber

My Feedback: (2)

No!! JR is Positive Shift and Futaba is Negative Shift. There are receivers from Hitec that have AutoShift and will work with either JR or Futaba. I believe that the new Hitec Aurora 9 will work with Hitec 2.4, JR 72 Mhz PPM, and Futaba 72 Mhz PPM.

BarracudaHockey

My Feedback: (11)

It was a round about route but we finally got there!

No.

Red Max

Thanks everyone. Thats what i wanted to know.

Rodney

Some transmitters allow you to have either positive or negative shift. If your futaba transmitter can be set up for positive shift, yes you can use it with the JR receiver.

JohnBuckner

My Feedback: (1)

His six channel FM Conquest has servo reversing and dual rates with only the low rates adjustable through manual pots on aileron and elevator and thats it.

It definately does not have shift selectability. Will function only with negative shift or negative shift selected receivers.

The old Conquest's all of them including the FM, AM, and the PCM versions are all long in the tooth and I would not trust any of them. Certainly not worth the investment of all new batterys. The rest of the airplane stuff you bought on another thread may be fine but this radio is not a buy at any price.

Check your servo plugs, They may look like this picture. If so these are the old 'G' plugs and you will not be able to use them in any modern Rx. This without a major hassle.

Some times these great deals or even freebys when it comes to radio systems can be expensive indeed.

This radio does have a trainer capability and switch but often with these old units the trim pots are so far off that that the buddy box and the master trims cannot be matched even at full trim pot delections.

Sorry someone needed to say it.

John

Red Max

Radio and receiver might be a good E-Bay project to auction off. I have other good radios in which I dont have to take any chances. What was the main issues with the old Conquest radios and receivers? This radio system came with an old trainer plane that a friend of mine had built as an ARF several years ago. It has an older K & B two stroke engine and all servos, the engine appears to be about a .50 size. Has good compression. He had a Global PT-19 that wal almost finished that had the same type of engine, and a .40 size Elder that was mostly finished. The trainer came with an extra fuselage. I also got a gas engine, cant tell what CC or what brand, appears to be around a 20 some cc range, I got everything for $50.00. I might try to sell the radio and receiver, or just use it in the old trainer, after I recover it and check all glue joints. I love to build and customize maby a little more than actual flying.

JohnBuckner

My Feedback: (1)

They were perfectly fine in their day but their day is long gone. I am no electronics expert but I do know that our radios do not last forever. And twentyyears and more is a lifetime for these radios. RF frequencys drift even sitting new in the box stick pots and trim pots corrode from disuse and become eratic.

Plastic gimble components dry up and fail.

John

Red Max

I thought about that , too. Thanks for the input. Better safe than sorry.

JohnBuckner

My Feedback: (1)

Red the K&B if it is a Sportster series the likely diplacement or size is .45 or .65, If it is the old standards it is a .40 or a .61 in any case they can be usefull engines. I just ran in a new in box .61 for a fellow yesterday and it dialed in nicely.

The Trainer could be one among hundreds litteraly. It also could be useful. Pictures could be the most help here to get useful thoughts. The Globle PT-19 I remember and may have flown some and I thing a nice flyer but best left untill becoming proficient with your trainer.

The Elder is a very cool kit built of a fantasy scale vintage type flyer of the early years of aviation. What that means is it is not a copy of any full scale orginal airplane but instead meant to represent an era in aviation but still fly well which it does indeed.

I built one years ago and it was a very sweet flyer, I think I finally gave it away, agine though it not a trainer so start with the trainer and get involved without fail with your local club or fellow flyers and find that mentor. This is key to you success.

John

Red Max

Well, actually, I am not a beginner, have been building kits, arfs, and flying on and off for several years. I am well beyond the trainer stage, but I still like to fly one once in a while "just for fun". This trainer's covering is in pretty bad shape, and I am going to strip it and check all glue joints. I have several airplanes in my hangar, my favorite is the Twist .40. Had a Twist 150 and traded it off, sorry I did that. I have not flown at all so far this summer, too many irons in the fire, but I am going to try to get some flights in before winter. I believe the K & B is around .50 size, as it is much bigger than a .40. The PT-19 is going to be a great project as well as the Elder (something to do this winter). I have the older orange colored Blue Max and the newer "New Generation" blue colored blue max. I made the new Blue Max to look like a Eindecker with the overhead wing wires and cowel. Back to the K & B, there is nothing on it anywhere that tells what size it is, but I believe the origional owner said it was a .50. (or so). I have a new Funtana .90 that I have almost completed, needs to be balanced and gone over completely one more time. Beautiful plane. I like 3d planes but I dont fly 3-D, mostly because they can be flown slow and handle really easy with a lot of exponential. I actually like them better than a trainer.

JohnBuckner

My Feedback: (1)

If there is no size indicated on K&B then that would seem to suggest that it is a Sportster series engine In which case it is either a .45 or a .65, Does it have a four bolt head? Some have the displacment stamped on the outside edge of the engine mount lugs and some had no stamp.

You will enjoy both the PT-19 and Elder

John

Red Max

Just got around to checking e-mails. Been out of pocket , couple of chores. I will check the head bolts. Absolutely could not see any stampings except K& B, but I will check again.