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JR 40 series transmitter

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Old 12-31-2002, 07:00 PM
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jim walker
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Default JR 40 series transmitter

I think it's a 4042. Anyway, The local hobby shop owner sells JR radios and says that switching crystals in the transmitter is OK even if he switches 10 or 20 channels away from what the transmitter was sold with from the factory. I read an article that stated the recievers don't care what frequency their on, but the transmitter is tuned at the factory to the crystal it's shipped with. The article went on to say that you could move up or down a couple of channels but after that you would progressively lose range the farther away you got from the factory setting. After many mishaps that were attributed to "interference", I mentioned to the local hobby shop owner what I just wrote and he said that may be true on other transmitters, but JR transmitters don't care what frequency they are on.

One of the mishaps was my plane, a very nice pylon racer that is now a bag of broken parts with all the radio gear destroyed. I asked what frequency the JR 40 series radio I bought from him was originally on, and he said it didn't matter so he didn't keep track of it.

Well, it's not worth it to me so I put the transmitter on the shelf until I could figure it out. I have a Hitec Flash 5 that is on 60 and has never had any "interference" much less a crash.

So with that background here are my questions. Is the article I read correct about JR transmitters in that they need to be tuned to the crystal? If so, what would it cost to get my transmitter changed to 60 and tuned?

Thanks, Jim
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Old 12-31-2002, 07:11 PM
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It is against FCC regulations to change the frequency of a transmitter except when performed by an authorized service center. This is true for all brands, with the only exception being systhesized systems. It would be the price of the crystal and a unit or 2 of labor for a crystal change only, which each unit of labor is $7.50, plus shipping. If any other parts or labor is required it would be higher than this.
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Old 12-31-2002, 07:28 PM
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Default JR 40 series transmitter

Wow! Thanks for the quick response. I'll assume that the "interference" is directly related to crystal switching even though you didn't directly answer that question. So what is the most efficient process and procedure to get my transmitter to an authorized service center for a crystal change and tune up? I want to do it ASAP and thanks again for your help.
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Old 12-31-2002, 07:42 PM
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Tough to say, I would say that it is not very likely, but the chance exists if the tuning was not checked. Fill out this form and send it in and we can take care of it from there. http://www.horizonhobby.com/media/pd...rchecklist.pdf
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Old 12-31-2002, 07:59 PM
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Default JR 40 series transmitter

Thanks for the form Danny, I'll send it in soon.

I base that statement on the following facts.

I've never been "hit" on my Flash 5 that is still on it's original frequency much less have the model go completely out of control for a long enough period to punch a hole in the ground.

The JR transmitter's that he has sold have all had their crystals changed from the original by simply removing the original from the back and plugging in another with no tuning or checking of any kind. The new frequency could be anywhere from 1 to 60 depending on what he has on hand in surplus. Of these transmitters, I've seen 4 planes go in now at two seperate locations where it was obviously not pilot error but total loss of communication. The latest was the owners brand new Dymond Tiger Moth with a $300 brushless in it. I watched him fly one airplane with no troubles, then change the crystal in the same transmitter to fly the Tiger Moth on a different frequency. The Moth flew great till it got a couple of hundred feet away and then it just augered in.

But if I understand you correctly, you are agreeing with him that changing crystals without tuning by an authorized service center (although against the law) doesn't affect the performance of the radio system......

I'm really confused now.
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Old 01-02-2003, 02:35 PM
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It is against the law to do so except when done by an authorized service center. It is likely that the changing of the crystals did not cause this problem though, but that chance exists when the output of the TX has not been checked.
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